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go / go / 198fc9a9eb7104d459bb5fea0aba5f2ff2c6f8d4 / . / src / cmd / compile / internal / gc / ssa.go
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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gc
import (
"bytes"
"fmt"
"html"
"os"
"strings"
"cmd/compile/internal/ssa"
"cmd/internal/obj"
"cmd/internal/obj/x86"
)
// buildssa builds an SSA function
// and reports whether it should be used.
// Once the SSA implementation is complete,
// it will never return nil, and the bool can be removed.
func buildssa(fn *Node) (ssafn *ssa.Func, usessa bool) {
name := fn.Func.Nname.Sym.Name
usessa = strings.HasSuffix(name, "_ssa") || name == os.Getenv("GOSSAFUNC")
if usessa {
fmt.Println("generating SSA for", name)
dumplist("buildssa-enter", fn.Func.Enter)
dumplist("buildssa-body", fn.Nbody)
}
var s state
s.pushLine(fn.Lineno)
defer s.popLine()
// TODO(khr): build config just once at the start of the compiler binary
var e ssaExport
e.log = usessa
s.config = ssa.NewConfig(Thearch.Thestring, &e)
s.f = s.config.NewFunc()
s.f.Name = name
if name == os.Getenv("GOSSAFUNC") {
// TODO: tempfile? it is handy to have the location
// of this file be stable, so you can just reload in the browser.
s.config.HTML = ssa.NewHTMLWriter("ssa.html", &s, name)
// TODO: generate and print a mapping from nodes to values and blocks
}
defer func() {
if !usessa {
s.config.HTML.Close()
}
}()
// If SSA support for the function is incomplete,
// assume that any panics are due to violated
// invariants. Swallow them silently.
defer func() {
if err := recover(); err != nil {
if !e.unimplemented {
panic(err)
}
}
}()
// We construct SSA using an algorithm similar to
// Brau, Buchwald, Hack, Leißa, Mallon, and Zwinkau
// http://pp.info.uni-karlsruhe.de/uploads/publikationen/braun13cc.pdf
// TODO: check this comment
// Allocate starting block
s.f.Entry = s.f.NewBlock(ssa.BlockPlain)
// Allocate exit block
s.exit = s.f.NewBlock(ssa.BlockExit)
// Allocate starting values
s.vars = map[*Node]*ssa.Value{}
s.labels = map[string]*ssaLabel{}
s.labeledNodes = map[*Node]*ssaLabel{}
s.startmem = s.entryNewValue0(ssa.OpArg, ssa.TypeMem)
s.sp = s.entryNewValue0(ssa.OpSP, Types[TUINTPTR]) // TODO: use generic pointer type (unsafe.Pointer?) instead
s.sb = s.entryNewValue0(ssa.OpSB, Types[TUINTPTR])
// Generate addresses of local declarations
s.decladdrs = map[*Node]*ssa.Value{}
for d := fn.Func.Dcl; d != nil; d = d.Next {
n := d.N
switch n.Class {
case PPARAM, PPARAMOUT:
aux := &ssa.ArgSymbol{Typ: n.Type, Offset: n.Xoffset, Sym: n.Sym}
s.decladdrs[n] = s.entryNewValue1A(ssa.OpAddr, Ptrto(n.Type), aux, s.sp)
case PAUTO:
aux := &ssa.AutoSymbol{Typ: n.Type, Offset: -1, Sym: n.Sym} // offset TBD by SSA pass
s.decladdrs[n] = s.entryNewValue1A(ssa.OpAddr, Ptrto(n.Type), aux, s.sp)
default:
str := ""
if n.Class&PHEAP != 0 {
str = ",heap"
}
s.Unimplementedf("local variable %v with class %s%s unimplemented", n, classnames[n.Class&^PHEAP], str)
}
}
// nodfp is a special argument which is the function's FP.
aux := &ssa.ArgSymbol{Typ: Types[TUINTPTR], Offset: 0, Sym: nodfp.Sym}
s.decladdrs[nodfp] = s.entryNewValue1A(ssa.OpAddr, Types[TUINTPTR], aux, s.sp)
// Convert the AST-based IR to the SSA-based IR
s.startBlock(s.f.Entry)
s.stmtList(fn.Func.Enter)
s.stmtList(fn.Nbody)
// fallthrough to exit
if b := s.endBlock(); b != nil {
addEdge(b, s.exit)
}
// Finish up exit block
s.startBlock(s.exit)
s.exit.Control = s.mem()
s.endBlock()
// Check that we used all labels
for name, lab := range s.labels {
if !lab.used() && !lab.reported {
yyerrorl(int(lab.defNode.Lineno), "label %v defined and not used", name)
lab.reported = true
}
if lab.used() && !lab.defined() && !lab.reported {
yyerrorl(int(lab.useNode.Lineno), "label %v not defined", name)
lab.reported = true
}
}
// Check any forward gotos. Non-forward gotos have already been checked.
for _, n := range s.fwdGotos {
lab := s.labels[n.Left.Sym.Name]
// If the label is undefined, we have already have printed an error.
if lab.defined() {
s.checkgoto(n, lab.defNode)
}
}
if nerrors > 0 {
return nil, false
}
// Link up variable uses to variable definitions
s.linkForwardReferences()
// Main call to ssa package to compile function
ssa.Compile(s.f)
// Calculate stats about what percentage of functions SSA handles.
if false {
fmt.Printf("SSA implemented: %t\n", !e.unimplemented)
}
if e.unimplemented {
return nil, false
}
// TODO: enable codegen more broadly once the codegen stabilizes
// and runtime support is in (gc maps, write barriers, etc.)
return s.f, usessa || localpkg.Name == os.Getenv("GOSSAPKG")
}
type state struct {
// configuration (arch) information
config *ssa.Config
// function we're building
f *ssa.Func
// exit block that "return" jumps to (and panics jump to)
exit *ssa.Block
// labels and labeled control flow nodes (OFOR, OSWITCH, OSELECT) in f
labels map[string]*ssaLabel
labeledNodes map[*Node]*ssaLabel
// gotos that jump forward; required for deferred checkgoto calls
fwdGotos []*Node
// unlabeled break and continue statement tracking
breakTo *ssa.Block // current target for plain break statement
continueTo *ssa.Block // current target for plain continue statement
// current location where we're interpreting the AST
curBlock *ssa.Block
// variable assignments in the current block (map from variable symbol to ssa value)
// *Node is the unique identifier (an ONAME Node) for the variable.
vars map[*Node]*ssa.Value
// all defined variables at the end of each block. Indexed by block ID.
defvars []map[*Node]*ssa.Value
// addresses of PPARAM, PPARAMOUT, and PAUTO variables.
decladdrs map[*Node]*ssa.Value
// starting values. Memory, frame pointer, and stack pointer
startmem *ssa.Value
sp *ssa.Value
sb *ssa.Value
// line number stack. The current line number is top of stack
line []int32
}
type ssaLabel struct {
target *ssa.Block // block identified by this label
breakTarget *ssa.Block // block to break to in control flow node identified by this label
continueTarget *ssa.Block // block to continue to in control flow node identified by this label
defNode *Node // label definition Node (OLABEL)
// Label use Node (OGOTO, OBREAK, OCONTINUE).
// Used only for error detection and reporting.
// There might be multiple uses, but we only need to track one.
useNode *Node
reported bool // reported indicates whether an error has already been reported for this label
}
// defined reports whether the label has a definition (OLABEL node).
func (l *ssaLabel) defined() bool { return l.defNode != nil }
// used reports whether the label has a use (OGOTO, OBREAK, or OCONTINUE node).
func (l *ssaLabel) used() bool { return l.useNode != nil }
// label returns the label associated with sym, creating it if necessary.
func (s *state) label(sym *Sym) *ssaLabel {
lab := s.labels[sym.Name]
if lab == nil {
lab = new(ssaLabel)
s.labels[sym.Name] = lab
}
return lab
}
func (s *state) Logf(msg string, args ...interface{}) { s.config.Logf(msg, args...) }
func (s *state) Fatalf(msg string, args ...interface{}) { s.config.Fatalf(msg, args...) }
func (s *state) Unimplementedf(msg string, args ...interface{}) { s.config.Unimplementedf(msg, args...) }
// dummy node for the memory variable
var memvar = Node{Op: ONAME, Sym: &Sym{Name: "mem"}}
// startBlock sets the current block we're generating code in to b.
func (s *state) startBlock(b *ssa.Block) {
if s.curBlock != nil {
s.Fatalf("starting block %v when block %v has not ended", b, s.curBlock)
}
s.curBlock = b
s.vars = map[*Node]*ssa.Value{}
}
// endBlock marks the end of generating code for the current block.
// Returns the (former) current block. Returns nil if there is no current
// block, i.e. if no code flows to the current execution point.
func (s *state) endBlock() *ssa.Block {
b := s.curBlock
if b == nil {
return nil
}
for len(s.defvars) <= int(b.ID) {
s.defvars = append(s.defvars, nil)
}
s.defvars[b.ID] = s.vars
s.curBlock = nil
s.vars = nil
b.Line = s.peekLine()
return b
}
// pushLine pushes a line number on the line number stack.
func (s *state) pushLine(line int32) {
s.line = append(s.line, line)
}
// popLine pops the top of the line number stack.
func (s *state) popLine() {
s.line = s.line[:len(s.line)-1]
}
// peekLine peek the top of the line number stack.
func (s *state) peekLine() int32 {
return s.line[len(s.line)-1]
}
func (s *state) Error(msg string, args ...interface{}) {
yyerrorl(int(s.peekLine()), msg, args...)
}
// newValue0 adds a new value with no arguments to the current block.
func (s *state) newValue0(op ssa.Op, t ssa.Type) *ssa.Value {
return s.curBlock.NewValue0(s.peekLine(), op, t)
}
// newValue0A adds a new value with no arguments and an aux value to the current block.
func (s *state) newValue0A(op ssa.Op, t ssa.Type, aux interface{}) *ssa.Value {
return s.curBlock.NewValue0A(s.peekLine(), op, t, aux)
}
// newValue1 adds a new value with one argument to the current block.
func (s *state) newValue1(op ssa.Op, t ssa.Type, arg *ssa.Value) *ssa.Value {
return s.curBlock.NewValue1(s.peekLine(), op, t, arg)
}
// newValue1A adds a new value with one argument and an aux value to the current block.
func (s *state) newValue1A(op ssa.Op, t ssa.Type, aux interface{}, arg *ssa.Value) *ssa.Value {
return s.curBlock.NewValue1A(s.peekLine(), op, t, aux, arg)
}
// newValue1I adds a new value with one argument and an auxint value to the current block.
func (s *state) newValue1I(op ssa.Op, t ssa.Type, aux int64, arg *ssa.Value) *ssa.Value {
return s.curBlock.NewValue1I(s.peekLine(), op, t, aux, arg)
}
// newValue2 adds a new value with two arguments to the current block.
func (s *state) newValue2(op ssa.Op, t ssa.Type, arg0, arg1 *ssa.Value) *ssa.Value {
return s.curBlock.NewValue2(s.peekLine(), op, t, arg0, arg1)
}
// newValue2I adds a new value with two arguments and an auxint value to the current block.
func (s *state) newValue2I(op ssa.Op, t ssa.Type, aux int64, arg0, arg1 *ssa.Value) *ssa.Value {
return s.curBlock.NewValue2I(s.peekLine(), op, t, aux, arg0, arg1)
}
// newValue3 adds a new value with three arguments to the current block.
func (s *state) newValue3(op ssa.Op, t ssa.Type, arg0, arg1, arg2 *ssa.Value) *ssa.Value {
return s.curBlock.NewValue3(s.peekLine(), op, t, arg0, arg1, arg2)
}
// entryNewValue adds a new value with no arguments to the entry block.
func (s *state) entryNewValue0(op ssa.Op, t ssa.Type) *ssa.Value {
return s.f.Entry.NewValue0(s.peekLine(), op, t)
}
// entryNewValue adds a new value with no arguments and an aux value to the entry block.
func (s *state) entryNewValue0A(op ssa.Op, t ssa.Type, aux interface{}) *ssa.Value {
return s.f.Entry.NewValue0A(s.peekLine(), op, t, aux)
}
// entryNewValue1 adds a new value with one argument to the entry block.
func (s *state) entryNewValue1(op ssa.Op, t ssa.Type, arg *ssa.Value) *ssa.Value {
return s.f.Entry.NewValue1(s.peekLine(), op, t, arg)
}
// entryNewValue1 adds a new value with one argument and an auxint value to the entry block.
func (s *state) entryNewValue1I(op ssa.Op, t ssa.Type, auxint int64, arg *ssa.Value) *ssa.Value {
return s.f.Entry.NewValue1I(s.peekLine(), op, t, auxint, arg)
}
// entryNewValue1A adds a new value with one argument and an aux value to the entry block.
func (s *state) entryNewValue1A(op ssa.Op, t ssa.Type, aux interface{}, arg *ssa.Value) *ssa.Value {
return s.f.Entry.NewValue1A(s.peekLine(), op, t, aux, arg)
}
// entryNewValue2 adds a new value with two arguments to the entry block.
func (s *state) entryNewValue2(op ssa.Op, t ssa.Type, arg0, arg1 *ssa.Value) *ssa.Value {
return s.f.Entry.NewValue2(s.peekLine(), op, t, arg0, arg1)
}
// constInt* routines add a new const int value to the entry block.
func (s *state) constInt8(t ssa.Type, c int8) *ssa.Value {
return s.f.ConstInt8(s.peekLine(), t, c)
}
func (s *state) constInt16(t ssa.Type, c int16) *ssa.Value {
return s.f.ConstInt16(s.peekLine(), t, c)
}
func (s *state) constInt32(t ssa.Type, c int32) *ssa.Value {
return s.f.ConstInt32(s.peekLine(), t, c)
}
func (s *state) constInt64(t ssa.Type, c int64) *ssa.Value {
return s.f.ConstInt64(s.peekLine(), t, c)
}
func (s *state) constIntPtr(t ssa.Type, c int64) *ssa.Value {
if s.config.PtrSize == 4 && int64(int32(c)) != c {
s.Fatalf("pointer constant too big %d", c)
}
return s.f.ConstIntPtr(s.peekLine(), t, c)
}
func (s *state) constInt(t ssa.Type, c int64) *ssa.Value {
if s.config.IntSize == 8 {
return s.constInt64(t, c)
}
if int64(int32(c)) != c {
s.Fatalf("integer constant too big %d", c)
}
return s.constInt32(t, int32(c))
}
// ssaStmtList converts the statement n to SSA and adds it to s.
func (s *state) stmtList(l *NodeList) {
for ; l != nil; l = l.Next {
s.stmt(l.N)
}
}
// ssaStmt converts the statement n to SSA and adds it to s.
func (s *state) stmt(n *Node) {
s.pushLine(n.Lineno)
defer s.popLine()
// If s.curBlock is nil, then we're about to generate dead code.
// We can't just short-circuit here, though,
// because we check labels and gotos as part of SSA generation.
// Provide a block for the dead code so that we don't have
// to add special cases everywhere else.
if s.curBlock == nil {
dead := s.f.NewBlock(ssa.BlockPlain)
s.startBlock(dead)
}
s.stmtList(n.Ninit)
switch n.Op {
case OBLOCK:
s.stmtList(n.List)
// No-ops
case OEMPTY, ODCLCONST, ODCLTYPE:
// Expression statements
case OCALLFUNC, OCALLMETH, OCALLINTER:
s.expr(n)
case ODCL:
if n.Left.Class&PHEAP == 0 {
return
}
if compiling_runtime != 0 {
Fatal("%v escapes to heap, not allowed in runtime.", n)
}
// TODO: the old pass hides the details of PHEAP
// variables behind ONAME nodes. Figure out if it's better
// to rewrite the tree and make the heapaddr construct explicit
// or to keep this detail hidden behind the scenes.
palloc := prealloc[n.Left]
if palloc == nil {
palloc = callnew(n.Left.Type)
prealloc[n.Left] = palloc
}
s.assign(OAS, n.Left.Name.Heapaddr, palloc)
case OLABEL:
sym := n.Left.Sym
if isblanksym(sym) {
// Empty identifier is valid but useless.
// See issues 11589, 11593.
return
}
lab := s.label(sym)
// Associate label with its control flow node, if any
if ctl := n.Name.Defn; ctl != nil {
switch ctl.Op {
case OFOR, OSWITCH, OSELECT:
s.labeledNodes[ctl] = lab
}
}
if !lab.defined() {
lab.defNode = n
} else {
s.Error("label %v already defined at %v", sym, Ctxt.Line(int(lab.defNode.Lineno)))
lab.reported = true
}
// The label might already have a target block via a goto.
if lab.target == nil {
lab.target = s.f.NewBlock(ssa.BlockPlain)
}
// go to that label (we pretend "label:" is preceded by "goto label")
b := s.endBlock()
addEdge(b, lab.target)
s.startBlock(lab.target)
case OGOTO:
sym := n.Left.Sym
lab := s.label(sym)
if lab.target == nil {
lab.target = s.f.NewBlock(ssa.BlockPlain)
}
if !lab.used() {
lab.useNode = n
}
if lab.defined() {
s.checkgoto(n, lab.defNode)
} else {
s.fwdGotos = append(s.fwdGotos, n)
}
b := s.endBlock()
addEdge(b, lab.target)
case OAS, OASWB:
// Check whether we can generate static data rather than code.
// If so, ignore n and defer data generation until codegen.
// Failure to do this causes writes to readonly symbols.
if gen_as_init(n, true) {
var data []*Node
if s.f.StaticData != nil {
data = s.f.StaticData.([]*Node)
}
s.f.StaticData = append(data, n)
return
}
s.assign(n.Op, n.Left, n.Right)
case OIF:
cond := s.expr(n.Left)
b := s.endBlock()
b.Kind = ssa.BlockIf
b.Control = cond
b.Likely = ssa.BranchPrediction(n.Likely) // gc and ssa both use -1/0/+1 for likeliness
bThen := s.f.NewBlock(ssa.BlockPlain)
bEnd := s.f.NewBlock(ssa.BlockPlain)
var bElse *ssa.Block
if n.Rlist == nil {
addEdge(b, bThen)
addEdge(b, bEnd)
} else {
bElse = s.f.NewBlock(ssa.BlockPlain)
addEdge(b, bThen)
addEdge(b, bElse)
}
s.startBlock(bThen)
s.stmtList(n.Nbody)
if b := s.endBlock(); b != nil {
addEdge(b, bEnd)
}
if n.Rlist != nil {
s.startBlock(bElse)
s.stmtList(n.Rlist)
if b := s.endBlock(); b != nil {
addEdge(b, bEnd)
}
}
s.startBlock(bEnd)
case ORETURN:
s.stmtList(n.List)
b := s.endBlock()
addEdge(b, s.exit)
case OCONTINUE, OBREAK:
var op string
var to *ssa.Block
switch n.Op {
case OCONTINUE:
op = "continue"
to = s.continueTo
case OBREAK:
op = "break"
to = s.breakTo
}
if n.Left == nil {
// plain break/continue
if to == nil {
s.Error("%s is not in a loop", op)
return
}
// nothing to do; "to" is already the correct target
} else {
// labeled break/continue; look up the target
sym := n.Left.Sym
lab := s.label(sym)
if !lab.used() {
lab.useNode = n.Left
}
if !lab.defined() {
s.Error("%s label not defined: %v", op, sym)
lab.reported = true
return
}
switch n.Op {
case OCONTINUE:
to = lab.continueTarget
case OBREAK:
to = lab.breakTarget
}
if to == nil {
// Valid label but not usable with a break/continue here, e.g.:
// for {
// continue abc
// }
// abc:
// for {}
s.Error("invalid %s label %v", op, sym)
lab.reported = true
return
}
}
b := s.endBlock()
addEdge(b, to)
case OFOR:
// OFOR: for Ninit; Left; Right { Nbody }
bCond := s.f.NewBlock(ssa.BlockPlain)
bBody := s.f.NewBlock(ssa.BlockPlain)
bIncr := s.f.NewBlock(ssa.BlockPlain)
bEnd := s.f.NewBlock(ssa.BlockPlain)
// first, jump to condition test
b := s.endBlock()
addEdge(b, bCond)
// generate code to test condition
s.startBlock(bCond)
var cond *ssa.Value
if n.Left != nil {
cond = s.expr(n.Left)
} else {
cond = s.entryNewValue0A(ssa.OpConstBool, Types[TBOOL], true)
}
b = s.endBlock()
b.Kind = ssa.BlockIf
b.Control = cond
b.Likely = ssa.BranchLikely
addEdge(b, bBody)
addEdge(b, bEnd)
// set up for continue/break in body
prevContinue := s.continueTo
prevBreak := s.breakTo
s.continueTo = bIncr
s.breakTo = bEnd
lab := s.labeledNodes[n]
if lab != nil {
// labeled for loop
lab.continueTarget = bIncr
lab.breakTarget = bEnd
}
// generate body
s.startBlock(bBody)
s.stmtList(n.Nbody)
// tear down continue/break
s.continueTo = prevContinue
s.breakTo = prevBreak
if lab != nil {
lab.continueTarget = nil
lab.breakTarget = nil
}
// done with body, goto incr
if b := s.endBlock(); b != nil {
addEdge(b, bIncr)
}
// generate incr
s.startBlock(bIncr)
if n.Right != nil {
s.stmt(n.Right)
}
if b := s.endBlock(); b != nil {
addEdge(b, bCond)
}
s.startBlock(bEnd)
case OSWITCH, OSELECT:
// These have been mostly rewritten by the front end into their Nbody fields.
// Our main task is to correctly hook up any break statements.
bEnd := s.f.NewBlock(ssa.BlockPlain)
prevBreak := s.breakTo
s.breakTo = bEnd
lab := s.labeledNodes[n]
if lab != nil {
// labeled
lab.breakTarget = bEnd
}
// generate body code
s.stmtList(n.Nbody)
s.breakTo = prevBreak
if lab != nil {
lab.breakTarget = nil
}
if b := s.endBlock(); b != nil {
addEdge(b, bEnd)
}
s.startBlock(bEnd)
case OVARKILL:
// TODO(khr): ??? anything to do here? Only for addrtaken variables?
// Maybe just link it in the store chain?
default:
s.Unimplementedf("unhandled stmt %s", opnames[n.Op])
}
}
type opAndType struct {
op uint8
etype uint8
}
var opToSSA = map[opAndType]ssa.Op{
opAndType{OADD, TINT8}: ssa.OpAdd8,
opAndType{OADD, TUINT8}: ssa.OpAdd8,
opAndType{OADD, TINT16}: ssa.OpAdd16,
opAndType{OADD, TUINT16}: ssa.OpAdd16,
opAndType{OADD, TINT32}: ssa.OpAdd32,
opAndType{OADD, TUINT32}: ssa.OpAdd32,
opAndType{OADD, TPTR32}: ssa.OpAdd32,
opAndType{OADD, TINT64}: ssa.OpAdd64,
opAndType{OADD, TUINT64}: ssa.OpAdd64,
opAndType{OADD, TPTR64}: ssa.OpAdd64,
opAndType{OSUB, TINT8}: ssa.OpSub8,
opAndType{OSUB, TUINT8}: ssa.OpSub8,
opAndType{OSUB, TINT16}: ssa.OpSub16,
opAndType{OSUB, TUINT16}: ssa.OpSub16,
opAndType{OSUB, TINT32}: ssa.OpSub32,
opAndType{OSUB, TUINT32}: ssa.OpSub32,
opAndType{OSUB, TINT64}: ssa.OpSub64,
opAndType{OSUB, TUINT64}: ssa.OpSub64,
opAndType{ONOT, TBOOL}: ssa.OpNot,
opAndType{OMINUS, TINT8}: ssa.OpNeg8,
opAndType{OMINUS, TUINT8}: ssa.OpNeg8,
opAndType{OMINUS, TINT16}: ssa.OpNeg16,
opAndType{OMINUS, TUINT16}: ssa.OpNeg16,
opAndType{OMINUS, TINT32}: ssa.OpNeg32,
opAndType{OMINUS, TUINT32}: ssa.OpNeg32,
opAndType{OMINUS, TINT64}: ssa.OpNeg64,
opAndType{OMINUS, TUINT64}: ssa.OpNeg64,
opAndType{OCOM, TINT8}: ssa.OpCom8,
opAndType{OCOM, TUINT8}: ssa.OpCom8,
opAndType{OCOM, TINT16}: ssa.OpCom16,
opAndType{OCOM, TUINT16}: ssa.OpCom16,
opAndType{OCOM, TINT32}: ssa.OpCom32,
opAndType{OCOM, TUINT32}: ssa.OpCom32,
opAndType{OCOM, TINT64}: ssa.OpCom64,
opAndType{OCOM, TUINT64}: ssa.OpCom64,
opAndType{OMUL, TINT8}: ssa.OpMul8,
opAndType{OMUL, TUINT8}: ssa.OpMul8,
opAndType{OMUL, TINT16}: ssa.OpMul16,
opAndType{OMUL, TUINT16}: ssa.OpMul16,
opAndType{OMUL, TINT32}: ssa.OpMul32,
opAndType{OMUL, TUINT32}: ssa.OpMul32,
opAndType{OMUL, TINT64}: ssa.OpMul64,
opAndType{OMUL, TUINT64}: ssa.OpMul64,
opAndType{OAND, TINT8}: ssa.OpAnd8,
opAndType{OAND, TUINT8}: ssa.OpAnd8,
opAndType{OAND, TINT16}: ssa.OpAnd16,
opAndType{OAND, TUINT16}: ssa.OpAnd16,
opAndType{OAND, TINT32}: ssa.OpAnd32,
opAndType{OAND, TUINT32}: ssa.OpAnd32,
opAndType{OAND, TINT64}: ssa.OpAnd64,
opAndType{OAND, TUINT64}: ssa.OpAnd64,
opAndType{OOR, TINT8}: ssa.OpOr8,
opAndType{OOR, TUINT8}: ssa.OpOr8,
opAndType{OOR, TINT16}: ssa.OpOr16,
opAndType{OOR, TUINT16}: ssa.OpOr16,
opAndType{OOR, TINT32}: ssa.OpOr32,
opAndType{OOR, TUINT32}: ssa.OpOr32,
opAndType{OOR, TINT64}: ssa.OpOr64,
opAndType{OOR, TUINT64}: ssa.OpOr64,
opAndType{OXOR, TINT8}: ssa.OpXor8,
opAndType{OXOR, TUINT8}: ssa.OpXor8,
opAndType{OXOR, TINT16}: ssa.OpXor16,
opAndType{OXOR, TUINT16}: ssa.OpXor16,
opAndType{OXOR, TINT32}: ssa.OpXor32,
opAndType{OXOR, TUINT32}: ssa.OpXor32,
opAndType{OXOR, TINT64}: ssa.OpXor64,
opAndType{OXOR, TUINT64}: ssa.OpXor64,
opAndType{OEQ, TBOOL}: ssa.OpEq8,
opAndType{OEQ, TINT8}: ssa.OpEq8,
opAndType{OEQ, TUINT8}: ssa.OpEq8,
opAndType{OEQ, TINT16}: ssa.OpEq16,
opAndType{OEQ, TUINT16}: ssa.OpEq16,
opAndType{OEQ, TINT32}: ssa.OpEq32,
opAndType{OEQ, TUINT32}: ssa.OpEq32,
opAndType{OEQ, TINT64}: ssa.OpEq64,
opAndType{OEQ, TUINT64}: ssa.OpEq64,
opAndType{OEQ, TPTR64}: ssa.OpEq64,
opAndType{OEQ, TINTER}: ssa.OpEqFat, // e == nil only
opAndType{OEQ, TARRAY}: ssa.OpEqFat, // slice only; a == nil only
opAndType{OEQ, TFUNC}: ssa.OpEqPtr,
opAndType{OEQ, TMAP}: ssa.OpEqPtr,
opAndType{OEQ, TCHAN}: ssa.OpEqPtr,
opAndType{OEQ, TUINTPTR}: ssa.OpEqPtr,
opAndType{OEQ, TUNSAFEPTR}: ssa.OpEqPtr,
opAndType{ONE, TBOOL}: ssa.OpNeq8,
opAndType{ONE, TINT8}: ssa.OpNeq8,
opAndType{ONE, TUINT8}: ssa.OpNeq8,
opAndType{ONE, TINT16}: ssa.OpNeq16,
opAndType{ONE, TUINT16}: ssa.OpNeq16,
opAndType{ONE, TINT32}: ssa.OpNeq32,
opAndType{ONE, TUINT32}: ssa.OpNeq32,
opAndType{ONE, TINT64}: ssa.OpNeq64,
opAndType{ONE, TUINT64}: ssa.OpNeq64,
opAndType{ONE, TPTR64}: ssa.OpNeq64,
opAndType{ONE, TINTER}: ssa.OpNeqFat, // e != nil only
opAndType{ONE, TARRAY}: ssa.OpNeqFat, // slice only; a != nil only
opAndType{ONE, TFUNC}: ssa.OpNeqPtr,
opAndType{ONE, TMAP}: ssa.OpNeqPtr,
opAndType{ONE, TCHAN}: ssa.OpNeqPtr,
opAndType{ONE, TUINTPTR}: ssa.OpNeqPtr,
opAndType{ONE, TUNSAFEPTR}: ssa.OpNeqPtr,
opAndType{OLT, TINT8}: ssa.OpLess8,
opAndType{OLT, TUINT8}: ssa.OpLess8U,
opAndType{OLT, TINT16}: ssa.OpLess16,
opAndType{OLT, TUINT16}: ssa.OpLess16U,
opAndType{OLT, TINT32}: ssa.OpLess32,
opAndType{OLT, TUINT32}: ssa.OpLess32U,
opAndType{OLT, TINT64}: ssa.OpLess64,
opAndType{OLT, TUINT64}: ssa.OpLess64U,
opAndType{OGT, TINT8}: ssa.OpGreater8,
opAndType{OGT, TUINT8}: ssa.OpGreater8U,
opAndType{OGT, TINT16}: ssa.OpGreater16,
opAndType{OGT, TUINT16}: ssa.OpGreater16U,
opAndType{OGT, TINT32}: ssa.OpGreater32,
opAndType{OGT, TUINT32}: ssa.OpGreater32U,
opAndType{OGT, TINT64}: ssa.OpGreater64,
opAndType{OGT, TUINT64}: ssa.OpGreater64U,
opAndType{OLE, TINT8}: ssa.OpLeq8,
opAndType{OLE, TUINT8}: ssa.OpLeq8U,
opAndType{OLE, TINT16}: ssa.OpLeq16,
opAndType{OLE, TUINT16}: ssa.OpLeq16U,
opAndType{OLE, TINT32}: ssa.OpLeq32,
opAndType{OLE, TUINT32}: ssa.OpLeq32U,
opAndType{OLE, TINT64}: ssa.OpLeq64,
opAndType{OLE, TUINT64}: ssa.OpLeq64U,
opAndType{OGE, TINT8}: ssa.OpGeq8,
opAndType{OGE, TUINT8}: ssa.OpGeq8U,
opAndType{OGE, TINT16}: ssa.OpGeq16,
opAndType{OGE, TUINT16}: ssa.OpGeq16U,
opAndType{OGE, TINT32}: ssa.OpGeq32,
opAndType{OGE, TUINT32}: ssa.OpGeq32U,
opAndType{OGE, TINT64}: ssa.OpGeq64,
opAndType{OGE, TUINT64}: ssa.OpGeq64U,
opAndType{OLROT, TUINT8}: ssa.OpLrot8,
opAndType{OLROT, TUINT16}: ssa.OpLrot16,
opAndType{OLROT, TUINT32}: ssa.OpLrot32,
opAndType{OLROT, TUINT64}: ssa.OpLrot64,
}
func (s *state) concreteEtype(t *Type) uint8 {
e := t.Etype
switch e {
default:
return e
case TINT:
if s.config.IntSize == 8 {
return TINT64
}
return TINT32
case TUINT:
if s.config.IntSize == 8 {
return TUINT64
}
return TUINT32
case TUINTPTR:
if s.config.PtrSize == 8 {
return TUINT64
}
return TUINT32
}
}
func (s *state) ssaOp(op uint8, t *Type) ssa.Op {
etype := s.concreteEtype(t)
x, ok := opToSSA[opAndType{op, etype}]
if !ok {
s.Unimplementedf("unhandled binary op %s etype=%s", opnames[op], Econv(int(etype), 0))
}
return x
}
type opAndTwoTypes struct {
op uint8
etype1 uint8
etype2 uint8
}
var shiftOpToSSA = map[opAndTwoTypes]ssa.Op{
opAndTwoTypes{OLSH, TINT8, TUINT8}: ssa.OpLsh8x8,
opAndTwoTypes{OLSH, TUINT8, TUINT8}: ssa.OpLsh8x8,
opAndTwoTypes{OLSH, TINT8, TUINT16}: ssa.OpLsh8x16,
opAndTwoTypes{OLSH, TUINT8, TUINT16}: ssa.OpLsh8x16,
opAndTwoTypes{OLSH, TINT8, TUINT32}: ssa.OpLsh8x32,
opAndTwoTypes{OLSH, TUINT8, TUINT32}: ssa.OpLsh8x32,
opAndTwoTypes{OLSH, TINT8, TUINT64}: ssa.OpLsh8x64,
opAndTwoTypes{OLSH, TUINT8, TUINT64}: ssa.OpLsh8x64,
opAndTwoTypes{OLSH, TINT16, TUINT8}: ssa.OpLsh16x8,
opAndTwoTypes{OLSH, TUINT16, TUINT8}: ssa.OpLsh16x8,
opAndTwoTypes{OLSH, TINT16, TUINT16}: ssa.OpLsh16x16,
opAndTwoTypes{OLSH, TUINT16, TUINT16}: ssa.OpLsh16x16,
opAndTwoTypes{OLSH, TINT16, TUINT32}: ssa.OpLsh16x32,
opAndTwoTypes{OLSH, TUINT16, TUINT32}: ssa.OpLsh16x32,
opAndTwoTypes{OLSH, TINT16, TUINT64}: ssa.OpLsh16x64,
opAndTwoTypes{OLSH, TUINT16, TUINT64}: ssa.OpLsh16x64,
opAndTwoTypes{OLSH, TINT32, TUINT8}: ssa.OpLsh32x8,
opAndTwoTypes{OLSH, TUINT32, TUINT8}: ssa.OpLsh32x8,
opAndTwoTypes{OLSH, TINT32, TUINT16}: ssa.OpLsh32x16,
opAndTwoTypes{OLSH, TUINT32, TUINT16}: ssa.OpLsh32x16,
opAndTwoTypes{OLSH, TINT32, TUINT32}: ssa.OpLsh32x32,
opAndTwoTypes{OLSH, TUINT32, TUINT32}: ssa.OpLsh32x32,
opAndTwoTypes{OLSH, TINT32, TUINT64}: ssa.OpLsh32x64,
opAndTwoTypes{OLSH, TUINT32, TUINT64}: ssa.OpLsh32x64,
opAndTwoTypes{OLSH, TINT64, TUINT8}: ssa.OpLsh64x8,
opAndTwoTypes{OLSH, TUINT64, TUINT8}: ssa.OpLsh64x8,
opAndTwoTypes{OLSH, TINT64, TUINT16}: ssa.OpLsh64x16,
opAndTwoTypes{OLSH, TUINT64, TUINT16}: ssa.OpLsh64x16,
opAndTwoTypes{OLSH, TINT64, TUINT32}: ssa.OpLsh64x32,
opAndTwoTypes{OLSH, TUINT64, TUINT32}: ssa.OpLsh64x32,
opAndTwoTypes{OLSH, TINT64, TUINT64}: ssa.OpLsh64x64,
opAndTwoTypes{OLSH, TUINT64, TUINT64}: ssa.OpLsh64x64,
opAndTwoTypes{ORSH, TINT8, TUINT8}: ssa.OpRsh8x8,
opAndTwoTypes{ORSH, TUINT8, TUINT8}: ssa.OpRsh8Ux8,
opAndTwoTypes{ORSH, TINT8, TUINT16}: ssa.OpRsh8x16,
opAndTwoTypes{ORSH, TUINT8, TUINT16}: ssa.OpRsh8Ux16,
opAndTwoTypes{ORSH, TINT8, TUINT32}: ssa.OpRsh8x32,
opAndTwoTypes{ORSH, TUINT8, TUINT32}: ssa.OpRsh8Ux32,
opAndTwoTypes{ORSH, TINT8, TUINT64}: ssa.OpRsh8x64,
opAndTwoTypes{ORSH, TUINT8, TUINT64}: ssa.OpRsh8Ux64,
opAndTwoTypes{ORSH, TINT16, TUINT8}: ssa.OpRsh16x8,
opAndTwoTypes{ORSH, TUINT16, TUINT8}: ssa.OpRsh16Ux8,
opAndTwoTypes{ORSH, TINT16, TUINT16}: ssa.OpRsh16x16,
opAndTwoTypes{ORSH, TUINT16, TUINT16}: ssa.OpRsh16Ux16,
opAndTwoTypes{ORSH, TINT16, TUINT32}: ssa.OpRsh16x32,
opAndTwoTypes{ORSH, TUINT16, TUINT32}: ssa.OpRsh16Ux32,
opAndTwoTypes{ORSH, TINT16, TUINT64}: ssa.OpRsh16x64,
opAndTwoTypes{ORSH, TUINT16, TUINT64}: ssa.OpRsh16Ux64,
opAndTwoTypes{ORSH, TINT32, TUINT8}: ssa.OpRsh32x8,
opAndTwoTypes{ORSH, TUINT32, TUINT8}: ssa.OpRsh32Ux8,
opAndTwoTypes{ORSH, TINT32, TUINT16}: ssa.OpRsh32x16,
opAndTwoTypes{ORSH, TUINT32, TUINT16}: ssa.OpRsh32Ux16,
opAndTwoTypes{ORSH, TINT32, TUINT32}: ssa.OpRsh32x32,
opAndTwoTypes{ORSH, TUINT32, TUINT32}: ssa.OpRsh32Ux32,
opAndTwoTypes{ORSH, TINT32, TUINT64}: ssa.OpRsh32x64,
opAndTwoTypes{ORSH, TUINT32, TUINT64}: ssa.OpRsh32Ux64,
opAndTwoTypes{ORSH, TINT64, TUINT8}: ssa.OpRsh64x8,
opAndTwoTypes{ORSH, TUINT64, TUINT8}: ssa.OpRsh64Ux8,
opAndTwoTypes{ORSH, TINT64, TUINT16}: ssa.OpRsh64x16,
opAndTwoTypes{ORSH, TUINT64, TUINT16}: ssa.OpRsh64Ux16,
opAndTwoTypes{ORSH, TINT64, TUINT32}: ssa.OpRsh64x32,
opAndTwoTypes{ORSH, TUINT64, TUINT32}: ssa.OpRsh64Ux32,
opAndTwoTypes{ORSH, TINT64, TUINT64}: ssa.OpRsh64x64,
opAndTwoTypes{ORSH, TUINT64, TUINT64}: ssa.OpRsh64Ux64,
}
func (s *state) ssaShiftOp(op uint8, t *Type, u *Type) ssa.Op {
etype1 := s.concreteEtype(t)
etype2 := s.concreteEtype(u)
x, ok := shiftOpToSSA[opAndTwoTypes{op, etype1, etype2}]
if !ok {
s.Unimplementedf("unhandled shift op %s etype=%s/%s", opnames[op], Econv(int(etype1), 0), Econv(int(etype2), 0))
}
return x
}
func (s *state) ssaRotateOp(op uint8, t *Type) ssa.Op {
etype1 := s.concreteEtype(t)
x, ok := opToSSA[opAndType{op, etype1}]
if !ok {
s.Unimplementedf("unhandled rotate op %s etype=%s", opnames[op], Econv(int(etype1), 0))
}
return x
}
// expr converts the expression n to ssa, adds it to s and returns the ssa result.
func (s *state) expr(n *Node) *ssa.Value {
s.pushLine(n.Lineno)
defer s.popLine()
s.stmtList(n.Ninit)
switch n.Op {
case ONAME:
if n.Class == PFUNC {
// "value" of a function is the address of the function's closure
sym := funcsym(n.Sym)
aux := &ssa.ExternSymbol{n.Type, sym}
return s.entryNewValue1A(ssa.OpAddr, Ptrto(n.Type), aux, s.sb)
}
if canSSA(n) {
return s.variable(n, n.Type)
}
addr := s.addr(n)
return s.newValue2(ssa.OpLoad, n.Type, addr, s.mem())
case OLITERAL:
switch n.Val().Ctype() {
case CTINT:
i := Mpgetfix(n.Val().U.(*Mpint))
switch n.Type.Size() {
case 1:
return s.constInt8(n.Type, int8(i))
case 2:
return s.constInt16(n.Type, int16(i))
case 4:
return s.constInt32(n.Type, int32(i))
case 8:
return s.constInt64(n.Type, i)
default:
s.Fatalf("bad integer size %d", n.Type.Size())
return nil
}
case CTSTR:
return s.entryNewValue0A(ssa.OpConstString, n.Type, n.Val().U)
case CTBOOL:
return s.entryNewValue0A(ssa.OpConstBool, n.Type, n.Val().U)
case CTNIL:
return s.entryNewValue0(ssa.OpConstNil, n.Type)
default:
s.Unimplementedf("unhandled OLITERAL %v", n.Val().Ctype())
return nil
}
case OCONVNOP:
to := n.Type
from := n.Left.Type
if to.Etype == TFUNC {
s.Unimplementedf("CONVNOP closure %v -> %v", n.Type, n.Left.Type)
return nil
}
// Assume everything will work out, so set up our return value.
// Anything interesting that happens from here is a fatal.
x := s.expr(n.Left)
v := s.newValue1(ssa.OpCopy, to, x) // ensure that v has the right type
// named <--> unnamed type or typed <--> untyped const
if from.Etype == to.Etype {
return v
}
// unsafe.Pointer <--> *T
if to.Etype == TUNSAFEPTR && from.IsPtr() || from.Etype == TUNSAFEPTR && to.IsPtr() {
return v
}
dowidth(from)
dowidth(to)
if from.Width != to.Width {
s.Fatalf("CONVNOP width mismatch %v (%d) -> %v (%d)\n", from, from.Width, to, to.Width)
return nil
}
if etypesign(from.Etype) != etypesign(to.Etype) {
s.Fatalf("CONVNOP sign mismatch %v (%s) -> %v (%s)\n", from, Econv(int(from.Etype), 0), to, Econv(int(to.Etype), 0))
return nil
}
if flag_race != 0 {
s.Unimplementedf("questionable CONVNOP from race detector %v -> %v\n", from, to)
return nil
}
if etypesign(from.Etype) == 0 {
s.Fatalf("CONVNOP unrecognized non-integer %v -> %v\n", from, to)
return nil
}
// integer, same width, same sign
return v
case OCONV:
x := s.expr(n.Left)
ft := n.Left.Type // from type
tt := n.Type // to type
if ft.IsInteger() && tt.IsInteger() {
var op ssa.Op
if tt.Size() == ft.Size() {
op = ssa.OpCopy
} else if tt.Size() < ft.Size() {
// truncation
switch 10*ft.Size() + tt.Size() {
case 21:
op = ssa.OpTrunc16to8
case 41:
op = ssa.OpTrunc32to8
case 42:
op = ssa.OpTrunc32to16
case 81:
op = ssa.OpTrunc64to8
case 82:
op = ssa.OpTrunc64to16
case 84:
op = ssa.OpTrunc64to32
default:
s.Fatalf("weird integer truncation %s -> %s", ft, tt)
}
} else if ft.IsSigned() {
// sign extension
switch 10*ft.Size() + tt.Size() {
case 12:
op = ssa.OpSignExt8to16
case 14:
op = ssa.OpSignExt8to32
case 18:
op = ssa.OpSignExt8to64
case 24:
op = ssa.OpSignExt16to32
case 28:
op = ssa.OpSignExt16to64
case 48:
op = ssa.OpSignExt32to64
default:
s.Fatalf("bad integer sign extension %s -> %s", ft, tt)
}
} else {
// zero extension
switch 10*ft.Size() + tt.Size() {
case 12:
op = ssa.OpZeroExt8to16
case 14:
op = ssa.OpZeroExt8to32
case 18:
op = ssa.OpZeroExt8to64
case 24:
op = ssa.OpZeroExt16to32
case 28:
op = ssa.OpZeroExt16to64
case 48:
op = ssa.OpZeroExt32to64
default:
s.Fatalf("weird integer sign extension %s -> %s", ft, tt)
}
}
return s.newValue1(op, n.Type, x)
}
s.Unimplementedf("unhandled OCONV %s -> %s", n.Left.Type, n.Type)
return nil
// binary ops
case OLT, OEQ, ONE, OLE, OGE, OGT:
a := s.expr(n.Left)
b := s.expr(n.Right)
return s.newValue2(s.ssaOp(n.Op, n.Left.Type), Types[TBOOL], a, b)
case OADD, OAND, OMUL, OOR, OSUB, OXOR:
a := s.expr(n.Left)
b := s.expr(n.Right)
return s.newValue2(s.ssaOp(n.Op, n.Type), a.Type, a, b)
case OLSH, ORSH:
a := s.expr(n.Left)
b := s.expr(n.Right)
return s.newValue2(s.ssaShiftOp(n.Op, n.Type, n.Right.Type), a.Type, a, b)
case OLROT:
a := s.expr(n.Left)
i := n.Right.Int()
if i <= 0 || i >= n.Type.Size()*8 {
s.Fatalf("Wrong rotate distance for LROT, expected 1 through %d, saw %d", n.Type.Size()*8-1, i)
}
return s.newValue1I(s.ssaRotateOp(n.Op, n.Type), a.Type, i, a)
case OANDAND, OOROR:
// To implement OANDAND (and OOROR), we introduce a
// new temporary variable to hold the result. The
// variable is associated with the OANDAND node in the
// s.vars table (normally variables are only
// associated with ONAME nodes). We convert
// A && B
// to
// var = A
// if var {
// var = B
// }
// Using var in the subsequent block introduces the
// necessary phi variable.
el := s.expr(n.Left)
s.vars[n] = el
b := s.endBlock()
b.Kind = ssa.BlockIf
b.Control = el
// In theory, we should set b.Likely here based on context.
// However, gc only gives us likeliness hints
// in a single place, for plain OIF statements,
// and passing around context is finnicky, so don't bother for now.
bRight := s.f.NewBlock(ssa.BlockPlain)
bResult := s.f.NewBlock(ssa.BlockPlain)
if n.Op == OANDAND {
addEdge(b, bRight)
addEdge(b, bResult)
} else if n.Op == OOROR {
addEdge(b, bResult)
addEdge(b, bRight)
}
s.startBlock(bRight)
er := s.expr(n.Right)
s.vars[n] = er
b = s.endBlock()
addEdge(b, bResult)
s.startBlock(bResult)
return s.variable(n, n.Type)
// unary ops
case ONOT, OMINUS, OCOM:
a := s.expr(n.Left)
return s.newValue1(s.ssaOp(n.Op, n.Type), a.Type, a)
case OADDR:
return s.addr(n.Left)
case OINDREG:
if int(n.Reg) != Thearch.REGSP {
s.Unimplementedf("OINDREG of non-SP register %s in expr: %v", obj.Rconv(int(n.Reg)), n)
return nil
}
addr := s.entryNewValue1I(ssa.OpOffPtr, Ptrto(n.Type), n.Xoffset, s.sp)
return s.newValue2(ssa.OpLoad, n.Type, addr, s.mem())
case OIND:
p := s.expr(n.Left)
s.nilCheck(p)
return s.newValue2(ssa.OpLoad, n.Type, p, s.mem())
case ODOT:
v := s.expr(n.Left)
return s.newValue1I(ssa.OpStructSelect, n.Type, n.Xoffset, v)
case ODOTPTR:
p := s.expr(n.Left)
s.nilCheck(p)
p = s.newValue2(ssa.OpAddPtr, p.Type, p, s.constIntPtr(Types[TUINTPTR], n.Xoffset))
return s.newValue2(ssa.OpLoad, n.Type, p, s.mem())
case OINDEX:
if n.Left.Type.Bound >= 0 { // array or string
a := s.expr(n.Left)
i := s.expr(n.Right)
i = s.extendIndex(i)
var elemtype *Type
var len *ssa.Value
if n.Left.Type.IsString() {
len = s.newValue1(ssa.OpStringLen, Types[TINT], a)
elemtype = Types[TUINT8]
} else {
len = s.constInt(Types[TINT], n.Left.Type.Bound)
elemtype = n.Left.Type.Type
}
s.boundsCheck(i, len)
return s.newValue2(ssa.OpArrayIndex, elemtype, a, i)
} else { // slice
p := s.addr(n)
return s.newValue2(ssa.OpLoad, n.Left.Type.Type, p, s.mem())
}
case OLEN, OCAP:
switch {
case n.Left.Type.IsSlice():
op := ssa.OpSliceLen
if n.Op == OCAP {
op = ssa.OpSliceCap
}
return s.newValue1(op, Types[TINT], s.expr(n.Left))
case n.Left.Type.IsString(): // string; not reachable for OCAP
return s.newValue1(ssa.OpStringLen, Types[TINT], s.expr(n.Left))
default: // array
return s.constInt(Types[TINT], n.Left.Type.Bound)
}
case OSPTR:
a := s.expr(n.Left)
if n.Left.Type.IsSlice() {
return s.newValue1(ssa.OpSlicePtr, n.Type, a)
} else {
return s.newValue1(ssa.OpStringPtr, n.Type, a)
}
case OITAB:
a := s.expr(n.Left)
return s.newValue1(ssa.OpITab, n.Type, a)
case OCALLFUNC, OCALLMETH:
left := n.Left
static := left.Op == ONAME && left.Class == PFUNC
if n.Op == OCALLMETH {
// Rewrite to an OCALLFUNC: (p.f)(...) becomes (f)(p, ...)
// Take care not to modify the original AST.
if left.Op != ODOTMETH {
Fatal("OCALLMETH: n.Left not an ODOTMETH: %v", left)
}
newLeft := *left.Right
newLeft.Type = left.Type
if newLeft.Op == ONAME {
newLeft.Class = PFUNC
}
left = &newLeft
static = true
}
// evaluate closure
var closure *ssa.Value
if !static {
closure = s.expr(left)
}
// run all argument assignments
s.stmtList(n.List)
bNext := s.f.NewBlock(ssa.BlockPlain)
var call *ssa.Value
if static {
call = s.newValue1A(ssa.OpStaticCall, ssa.TypeMem, left.Sym, s.mem())
} else {
entry := s.newValue2(ssa.OpLoad, Types[TUINTPTR], closure, s.mem())
call = s.newValue3(ssa.OpClosureCall, ssa.TypeMem, entry, closure, s.mem())
}
dowidth(left.Type)
call.AuxInt = left.Type.Argwid // call operations carry the argsize of the callee along with them
s.vars[&memvar] = call
b := s.endBlock()
b.Kind = ssa.BlockCall
b.Control = call
addEdge(b, bNext)
addEdge(b, s.exit)
// read result from stack at the start of the fallthrough block
s.startBlock(bNext)
var titer Iter
fp := Structfirst(&titer, Getoutarg(left.Type))
if fp == nil {
// CALLFUNC has no return value. Continue with the next statement.
return nil
}
a := s.entryNewValue1I(ssa.OpOffPtr, Ptrto(fp.Type), fp.Width, s.sp)
return s.newValue2(ssa.OpLoad, fp.Type, a, call)
case OGETG:
return s.newValue0(ssa.OpGetG, n.Type)
default:
s.Unimplementedf("unhandled expr %s", opnames[n.Op])
return nil
}
}
func (s *state) assign(op uint8, left *Node, right *Node) {
// TODO: do write barrier
// if op == OASWB
var val *ssa.Value
if right == nil {
// right == nil means use the zero value of the assigned type.
t := left.Type
if !canSSA(left) {
// if we can't ssa this memory, treat it as just zeroing out the backing memory
addr := s.addr(left)
s.vars[&memvar] = s.newValue2I(ssa.OpZero, ssa.TypeMem, t.Size(), addr, s.mem())
return
}
val = s.zeroVal(t)
} else {
val = s.expr(right)
}
if left.Op == ONAME && canSSA(left) {
// Update variable assignment.
s.vars[left] = val
return
}
// not ssa-able. Treat as a store.
addr := s.addr(left)
s.vars[&memvar] = s.newValue3(ssa.OpStore, ssa.TypeMem, addr, val, s.mem())
}
// zeroVal returns the zero value for type t.
func (s *state) zeroVal(t *Type) *ssa.Value {
switch {
case t.IsInteger():
switch t.Size() {
case 1:
return s.constInt8(t, 0)
case 2:
return s.constInt16(t, 0)
case 4:
return s.constInt32(t, 0)
case 8:
return s.constInt64(t, 0)
default:
s.Fatalf("bad sized integer type %s", t)
}
case t.IsString():
return s.entryNewValue0A(ssa.OpConstString, t, "")
case t.IsPtr():
return s.entryNewValue0(ssa.OpConstNil, t)
case t.IsBoolean():
return s.entryNewValue0A(ssa.OpConstBool, t, false) // TODO: store bools as 0/1 in AuxInt?
}
s.Unimplementedf("zero for type %v not implemented", t)
return nil
}
// etypesign returns the signed-ness of e, for integer/pointer etypes.
// -1 means signed, +1 means unsigned, 0 means non-integer/non-pointer.
func etypesign(e uint8) int8 {
switch e {
case TINT8, TINT16, TINT32, TINT64, TINT:
return -1
case TUINT8, TUINT16, TUINT32, TUINT64, TUINT, TUINTPTR, TUNSAFEPTR:
return +1
}
return 0
}
// addr converts the address of the expression n to SSA, adds it to s and returns the SSA result.
// The value that the returned Value represents is guaranteed to be non-nil.
func (s *state) addr(n *Node) *ssa.Value {
switch n.Op {
case ONAME:
switch n.Class {
case PEXTERN:
// global variable
aux := &ssa.ExternSymbol{n.Type, n.Sym}
v := s.entryNewValue1A(ssa.OpAddr, Ptrto(n.Type), aux, s.sb)
// TODO: Make OpAddr use AuxInt as well as Aux.
if n.Xoffset != 0 {
v = s.entryNewValue1I(ssa.OpOffPtr, v.Type, n.Xoffset, v)
}
return v
case PPARAM, PPARAMOUT, PAUTO:
// parameter/result slot or local variable
v := s.decladdrs[n]
if v == nil {
if flag_race != 0 && n.String() == ".fp" {
s.Unimplementedf("race detector mishandles nodfp")
}
s.Fatalf("addr of undeclared ONAME %v. declared: %v", n, s.decladdrs)
}
return v
case PAUTO | PHEAP:
return s.expr(n.Name.Heapaddr)
default:
s.Unimplementedf("variable address of %v not implemented", n)
return nil
}
case OINDREG:
// indirect off a register
// used for storing/loading arguments/returns to/from callees
if int(n.Reg) != Thearch.REGSP {
s.Unimplementedf("OINDREG of non-SP register %s in addr: %v", obj.Rconv(int(n.Reg)), n)
return nil
}
return s.entryNewValue1I(ssa.OpOffPtr, Ptrto(n.Type), n.Xoffset, s.sp)
case OINDEX:
if n.Left.Type.IsSlice() {
a := s.expr(n.Left)
i := s.expr(n.Right)
i = s.extendIndex(i)
len := s.newValue1(ssa.OpSliceLen, Types[TUINTPTR], a)
s.boundsCheck(i, len)
p := s.newValue1(ssa.OpSlicePtr, Ptrto(n.Left.Type.Type), a)
return s.newValue2(ssa.OpPtrIndex, Ptrto(n.Left.Type.Type), p, i)
} else { // array
a := s.addr(n.Left)
i := s.expr(n.Right)
i = s.extendIndex(i)
len := s.constInt(Types[TINT], n.Left.Type.Bound)
s.boundsCheck(i, len)
return s.newValue2(ssa.OpPtrIndex, Ptrto(n.Left.Type.Type), a, i)
}
case OIND:
p := s.expr(n.Left)
s.nilCheck(p)
return p
case ODOT:
p := s.addr(n.Left)
return s.newValue2(ssa.OpAddPtr, p.Type, p, s.constIntPtr(Types[TUINTPTR], n.Xoffset))
case ODOTPTR:
p := s.expr(n.Left)
s.nilCheck(p)
return s.newValue2(ssa.OpAddPtr, p.Type, p, s.constIntPtr(Types[TUINTPTR], n.Xoffset))
default:
s.Unimplementedf("addr: bad op %v", Oconv(int(n.Op), 0))
return nil
}
}
// canSSA reports whether n is SSA-able.
// n must be an ONAME.
func canSSA(n *Node) bool {
if n.Op != ONAME {
return false
}
if n.Addrtaken {
return false
}
if n.Class&PHEAP != 0 {
return false
}
if n.Class == PEXTERN {
return false
}
if n.Class == PPARAMOUT {
return false
}
if Isfat(n.Type) {
return false
}
return true
// TODO: try to make more variables SSAable.
}
// nilCheck generates nil pointer checking code.
// Starts a new block on return, unless nil checks are disabled.
// Used only for automatically inserted nil checks,
// not for user code like 'x != nil'.
func (s *state) nilCheck(ptr *ssa.Value) {
if Disable_checknil != 0 {
return
}
c := s.newValue1(ssa.OpIsNonNil, Types[TBOOL], ptr)
b := s.endBlock()
b.Kind = ssa.BlockIf
b.Control = c
b.Likely = ssa.BranchLikely
bNext := s.f.NewBlock(ssa.BlockPlain)
bPanic := s.f.NewBlock(ssa.BlockPlain)
addEdge(b, bNext)
addEdge(b, bPanic)
addEdge(bPanic, s.exit)
s.startBlock(bPanic)
// TODO: implicit nil checks somehow?
s.vars[&memvar] = s.newValue2(ssa.OpPanicNilCheck, ssa.TypeMem, ptr, s.mem())
s.endBlock()
s.startBlock(bNext)
}
// boundsCheck generates bounds checking code. Checks if 0 <= idx < len, branches to exit if not.
// Starts a new block on return.
func (s *state) boundsCheck(idx, len *ssa.Value) {
// TODO: convert index to full width?
// TODO: if index is 64-bit and we're compiling to 32-bit, check that high 32 bits are zero.
// bounds check
cmp := s.newValue2(ssa.OpIsInBounds, Types[TBOOL], idx, len)
b := s.endBlock()
b.Kind = ssa.BlockIf
b.Control = cmp
b.Likely = ssa.BranchLikely
bNext := s.f.NewBlock(ssa.BlockPlain)
addEdge(b, bNext)
addEdge(b, s.exit)
// TODO: don't go directly to s.exit. Go to a stub that calls panicindex first.
s.startBlock(bNext)
}
// checkgoto checks that a goto from from to to does not
// jump into a block or jump over variable declarations.
// It is a copy of checkgoto in the pre-SSA backend,
// modified only for line number handling.
// TODO: document how this works and why it is designed the way it is.
func (s *state) checkgoto(from *Node, to *Node) {
if from.Sym == to.Sym {
return
}
nf := 0
for fs := from.Sym; fs != nil; fs = fs.Link {
nf++
}
nt := 0
for fs := to.Sym; fs != nil; fs = fs.Link {
nt++
}
fs := from.Sym
for ; nf > nt; nf-- {
fs = fs.Link
}
if fs != to.Sym {
// decide what to complain about.
// prefer to complain about 'into block' over declarations,
// so scan backward to find most recent block or else dcl.
var block *Sym
var dcl *Sym
ts := to.Sym
for ; nt > nf; nt-- {
if ts.Pkg == nil {
block = ts
} else {
dcl = ts
}
ts = ts.Link
}
for ts != fs {
if ts.Pkg == nil {
block = ts
} else {
dcl = ts
}
ts = ts.Link
fs = fs.Link
}
lno := int(from.Left.Lineno)
if block != nil {
yyerrorl(lno, "goto %v jumps into block starting at %v", from.Left.Sym, Ctxt.Line(int(block.Lastlineno)))
} else {
yyerrorl(lno, "goto %v jumps over declaration of %v at %v", from.Left.Sym, dcl, Ctxt.Line(int(dcl.Lastlineno)))
}
}
}
// variable returns the value of a variable at the current location.
func (s *state) variable(name *Node, t ssa.Type) *ssa.Value {
v := s.vars[name]
if v == nil {
// TODO: get type? Take Sym as arg?
v = s.newValue0A(ssa.OpFwdRef, t, name)
s.vars[name] = v
}
return v
}
func (s *state) mem() *ssa.Value {
return s.variable(&memvar, ssa.TypeMem)
}
func (s *state) linkForwardReferences() {
// Build ssa graph. Each variable on its first use in a basic block
// leaves a FwdRef in that block representing the incoming value
// of that variable. This function links that ref up with possible definitions,
// inserting Phi values as needed. This is essentially the algorithm
// described by Brau, Buchwald, Hack, Leißa, Mallon, and Zwinkau:
// http://pp.info.uni-karlsruhe.de/uploads/publikationen/braun13cc.pdf
for _, b := range s.f.Blocks {
for _, v := range b.Values {
if v.Op != ssa.OpFwdRef {
continue
}
name := v.Aux.(*Node)
v.Op = ssa.OpCopy
v.Aux = nil
v.SetArgs1(s.lookupVarIncoming(b, v.Type, name))
}
}
}
// lookupVarIncoming finds the variable's value at the start of block b.
func (s *state) lookupVarIncoming(b *ssa.Block, t ssa.Type, name *Node) *ssa.Value {
// TODO(khr): have lookupVarIncoming overwrite the fwdRef or copy it
// will be used in, instead of having the result used in a copy value.
if b == s.f.Entry {
if name == &memvar {
return s.startmem
}
// variable is live at the entry block. Load it.
addr := s.decladdrs[name]
if addr == nil {
// TODO: closure args reach here.
s.Unimplementedf("variable %s not found", name)
}
if _, ok := addr.Aux.(*ssa.ArgSymbol); !ok {
s.Fatalf("variable live at start of function %s is not an argument %s", b.Func.Name, name)
}
return s.entryNewValue2(ssa.OpLoad, t, addr, s.startmem)
}
var vals []*ssa.Value
for _, p := range b.Preds {
vals = append(vals, s.lookupVarOutgoing(p, t, name))
}
if len(vals) == 0 {
// This block is dead; we have no predecessors and we're not the entry block.
// It doesn't matter what we use here as long as it is well-formed,
// so use the default/zero value.
if name == &memvar {
return s.startmem
}
return s.zeroVal(name.Type)
}
v0 := vals[0]
for i := 1; i < len(vals); i++ {
if vals[i] != v0 {
// need a phi value
v := b.NewValue0(s.peekLine(), ssa.OpPhi, t)
v.AddArgs(vals...)
return v
}
}
return v0
}
// lookupVarOutgoing finds the variable's value at the end of block b.
func (s *state) lookupVarOutgoing(b *ssa.Block, t ssa.Type, name *Node) *ssa.Value {
m := s.defvars[b.ID]
if v, ok := m[name]; ok {
return v
}
// The variable is not defined by b and we haven't
// looked it up yet. Generate v, a copy value which
// will be the outgoing value of the variable. Then
// look up w, the incoming value of the variable.
// Make v = copy(w). We need the extra copy to
// prevent infinite recursion when looking up the
// incoming value of the variable.
v := b.NewValue0(s.peekLine(), ssa.OpCopy, t)
m[name] = v
v.AddArg(s.lookupVarIncoming(b, t, name))
return v
}
// TODO: the above mutually recursive functions can lead to very deep stacks. Fix that.
// addEdge adds an edge from b to c.
func addEdge(b, c *ssa.Block) {
b.Succs = append(b.Succs, c)
c.Preds = append(c.Preds, b)
}
// an unresolved branch
type branch struct {
p *obj.Prog // branch instruction
b *ssa.Block // target
}
// genssa appends entries to ptxt for each instruction in f.
// gcargs and gclocals are filled in with pointer maps for the frame.
func genssa(f *ssa.Func, ptxt *obj.Prog, gcargs, gclocals *Sym) {
// TODO: line numbers
if f.FrameSize > 1<<31 {
Yyerror("stack frame too large (>2GB)")
return
}
e := f.Config.Frontend().(*ssaExport)
// We're about to emit a bunch of Progs.
// Since the only way to get here is to explicitly request it,
// just fail on unimplemented instead of trying to unwind our mess.
e.mustImplement = true
ptxt.To.Type = obj.TYPE_TEXTSIZE
ptxt.To.Val = int32(Rnd(Curfn.Type.Argwid, int64(Widthptr))) // arg size
ptxt.To.Offset = f.FrameSize - 8 // TODO: arch-dependent
// Remember where each block starts.
bstart := make([]*obj.Prog, f.NumBlocks())
// Remember all the branch instructions we've seen
// and where they would like to go
var branches []branch
var valueProgs map[*obj.Prog]*ssa.Value
var blockProgs map[*obj.Prog]*ssa.Block
const logProgs = true
if logProgs {
valueProgs = make(map[*obj.Prog]*ssa.Value, f.NumValues())
blockProgs = make(map[*obj.Prog]*ssa.Block, f.NumBlocks())
f.Logf("genssa %s\n", f.Name)
blockProgs[Pc] = f.Blocks[0]
}
// Emit basic blocks
for i, b := range f.Blocks {
bstart[b.ID] = Pc
// Emit values in block
for _, v := range b.Values {
x := Pc
genValue(v)
if logProgs {
for ; x != Pc; x = x.Link {
valueProgs[x] = v
}
}
}
// Emit control flow instructions for block
var next *ssa.Block
if i < len(f.Blocks)-1 {
next = f.Blocks[i+1]
}
x := Pc
branches = genBlock(b, next, branches)
if logProgs {
for ; x != Pc; x = x.Link {
blockProgs[x] = b
}
}
}
// Resolve branches
for _, br := range branches {
br.p.To.Val = bstart[br.b.ID]
}
Pc.As = obj.ARET // overwrite AEND
if logProgs {
for p := ptxt; p != nil; p = p.Link {
var s string
if v, ok := valueProgs[p]; ok {
s = v.String()
} else if b, ok := blockProgs[p]; ok {
s = b.String()
} else {
s = " " // most value and branch strings are 2-3 characters long
}
f.Logf("%s\t%s\n", s, p)
}
if f.Config.HTML != nil {
saved := ptxt.Ctxt.LineHist.PrintFilenameOnly
ptxt.Ctxt.LineHist.PrintFilenameOnly = true
var buf bytes.Buffer
buf.WriteString("<code>")
buf.WriteString("<dl class=\"ssa-gen\">")
for p := ptxt; p != nil; p = p.Link {
buf.WriteString("<dt class=\"ssa-prog-src\">")
if v, ok := valueProgs[p]; ok {
buf.WriteString(v.HTML())
} else if b, ok := blockProgs[p]; ok {
buf.WriteString(b.HTML())
}
buf.WriteString("</dt>")
buf.WriteString("<dd class=\"ssa-prog\">")
buf.WriteString(html.EscapeString(p.String()))
buf.WriteString("</dd>")
buf.WriteString("</li>")
}
buf.WriteString("</dl>")
buf.WriteString("</code>")
f.Config.HTML.WriteColumn("genssa", buf.String())
ptxt.Ctxt.LineHist.PrintFilenameOnly = saved
}
}
// Emit static data
if f.StaticData != nil {
for _, n := range f.StaticData.([]*Node) {
if !gen_as_init(n, false) {
Fatal("non-static data marked as static: %v\n\n", n, f)
}
}
}
// TODO: liveness
// TODO: gcargs
// TODO: gclocals
// TODO: dump frame if -f
// Emit garbage collection symbols. TODO: put something in them
//liveness(Curfn, ptxt, gcargs, gclocals)
duint32(gcargs, 0, 0)
ggloblsym(gcargs, 4, obj.RODATA|obj.DUPOK)
duint32(gclocals, 0, 0)
ggloblsym(gclocals, 4, obj.RODATA|obj.DUPOK)
f.Config.HTML.Close()
}
func genValue(v *ssa.Value) {
lineno = v.Line
switch v.Op {
case ssa.OpAMD64ADDQ:
// TODO: use addq instead of leaq if target is in the right register.
p := Prog(x86.ALEAQ)
p.From.Type = obj.TYPE_MEM
p.From.Reg = regnum(v.Args[0])
p.From.Scale = 1
p.From.Index = regnum(v.Args[1])
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
case ssa.OpAMD64ADDL:
p := Prog(x86.ALEAL)
p.From.Type = obj.TYPE_MEM
p.From.Reg = regnum(v.Args[0])
p.From.Scale = 1
p.From.Index = regnum(v.Args[1])
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
case ssa.OpAMD64ADDW:
p := Prog(x86.ALEAW)
p.From.Type = obj.TYPE_MEM
p.From.Reg = regnum(v.Args[0])
p.From.Scale = 1
p.From.Index = regnum(v.Args[1])
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
// 2-address opcode arithmetic, symmetric
case ssa.OpAMD64ADDB,
ssa.OpAMD64ANDQ, ssa.OpAMD64ANDL, ssa.OpAMD64ANDW, ssa.OpAMD64ANDB,
ssa.OpAMD64ORQ, ssa.OpAMD64ORL, ssa.OpAMD64ORW, ssa.OpAMD64ORB,
ssa.OpAMD64XORQ, ssa.OpAMD64XORL, ssa.OpAMD64XORW, ssa.OpAMD64XORB,
ssa.OpAMD64MULQ, ssa.OpAMD64MULL, ssa.OpAMD64MULW, ssa.OpAMD64MULB:
r := regnum(v)
x := regnum(v.Args[0])
y := regnum(v.Args[1])
if x != r && y != r {
p := Prog(regMoveAMD64(v.Type.Size()))
p.From.Type = obj.TYPE_REG
p.From.Reg = x
p.To.Type = obj.TYPE_REG
p.To.Reg = r
x = r
}
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_REG
p.To.Type = obj.TYPE_REG
p.To.Reg = r
if x == r {
p.From.Reg = y
} else {
p.From.Reg = x
}
// 2-address opcode arithmetic, not symmetric
case ssa.OpAMD64SUBQ, ssa.OpAMD64SUBL, ssa.OpAMD64SUBW, ssa.OpAMD64SUBB:
r := regnum(v)
x := regnum(v.Args[0])
y := regnum(v.Args[1])
var neg bool
if y == r {
// compute -(y-x) instead
x, y = y, x
neg = true
}
if x != r {
p := Prog(regMoveAMD64(v.Type.Size()))
p.From.Type = obj.TYPE_REG
p.From.Reg = x
p.To.Type = obj.TYPE_REG
p.To.Reg = r
}
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_REG
p.To.Type = obj.TYPE_REG
p.To.Reg = r
p.From.Reg = y
if neg {
p := Prog(x86.ANEGQ) // TODO: use correct size? This is mostly a hack until regalloc does 2-address correctly
p.To.Type = obj.TYPE_REG
p.To.Reg = r
}
case ssa.OpAMD64SHLQ, ssa.OpAMD64SHLL, ssa.OpAMD64SHLW, ssa.OpAMD64SHLB,
ssa.OpAMD64SHRQ, ssa.OpAMD64SHRL, ssa.OpAMD64SHRW, ssa.OpAMD64SHRB,
ssa.OpAMD64SARQ, ssa.OpAMD64SARL, ssa.OpAMD64SARW, ssa.OpAMD64SARB:
x := regnum(v.Args[0])
r := regnum(v)
if x != r {
if r == x86.REG_CX {
v.Fatalf("can't implement %s, target and shift both in CX", v.LongString())
}
p := Prog(regMoveAMD64(v.Type.Size()))
p.From.Type = obj.TYPE_REG
p.From.Reg = x
p.To.Type = obj.TYPE_REG
p.To.Reg = r
}
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_REG
p.From.Reg = regnum(v.Args[1]) // should be CX
p.To.Type = obj.TYPE_REG
p.To.Reg = r
case ssa.OpAMD64ADDQconst, ssa.OpAMD64ADDLconst, ssa.OpAMD64ADDWconst:
// TODO: use addq instead of leaq if target is in the right register.
var asm int
switch v.Op {
case ssa.OpAMD64ADDQconst:
asm = x86.ALEAQ
case ssa.OpAMD64ADDLconst:
asm = x86.ALEAL
case ssa.OpAMD64ADDWconst:
asm = x86.ALEAW
}
p := Prog(asm)
p.From.Type = obj.TYPE_MEM
p.From.Reg = regnum(v.Args[0])
p.From.Offset = v.AuxInt
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
case ssa.OpAMD64MULQconst, ssa.OpAMD64MULLconst, ssa.OpAMD64MULWconst, ssa.OpAMD64MULBconst:
r := regnum(v)
x := regnum(v.Args[0])
if r != x {
p := Prog(regMoveAMD64(v.Type.Size()))
p.From.Type = obj.TYPE_REG
p.From.Reg = x
p.To.Type = obj.TYPE_REG
p.To.Reg = r
}
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_CONST
p.From.Offset = v.AuxInt
p.To.Type = obj.TYPE_REG
p.To.Reg = r
// TODO: Teach doasm to compile the three-address multiply imul $c, r1, r2
// instead of using the MOVQ above.
//p.From3 = new(obj.Addr)
//p.From3.Type = obj.TYPE_REG
//p.From3.Reg = regnum(v.Args[0])
case ssa.OpAMD64ADDBconst,
ssa.OpAMD64ANDQconst, ssa.OpAMD64ANDLconst, ssa.OpAMD64ANDWconst, ssa.OpAMD64ANDBconst,
ssa.OpAMD64ORQconst, ssa.OpAMD64ORLconst, ssa.OpAMD64ORWconst, ssa.OpAMD64ORBconst,
ssa.OpAMD64XORQconst, ssa.OpAMD64XORLconst, ssa.OpAMD64XORWconst, ssa.OpAMD64XORBconst,
ssa.OpAMD64SUBQconst, ssa.OpAMD64SUBLconst, ssa.OpAMD64SUBWconst, ssa.OpAMD64SUBBconst,
ssa.OpAMD64SHLQconst, ssa.OpAMD64SHLLconst, ssa.OpAMD64SHLWconst, ssa.OpAMD64SHLBconst,
ssa.OpAMD64SHRQconst, ssa.OpAMD64SHRLconst, ssa.OpAMD64SHRWconst, ssa.OpAMD64SHRBconst,
ssa.OpAMD64SARQconst, ssa.OpAMD64SARLconst, ssa.OpAMD64SARWconst, ssa.OpAMD64SARBconst,
ssa.OpAMD64ROLQconst, ssa.OpAMD64ROLLconst, ssa.OpAMD64ROLWconst, ssa.OpAMD64ROLBconst:
// This code compensates for the fact that the register allocator
// doesn't understand 2-address instructions yet. TODO: fix that.
x := regnum(v.Args[0])
r := regnum(v)
if x != r {
p := Prog(regMoveAMD64(v.Type.Size()))
p.From.Type = obj.TYPE_REG
p.From.Reg = x
p.To.Type = obj.TYPE_REG
p.To.Reg = r
}
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_CONST
p.From.Offset = v.AuxInt
p.To.Type = obj.TYPE_REG
p.To.Reg = r
case ssa.OpAMD64SBBQcarrymask, ssa.OpAMD64SBBLcarrymask:
r := regnum(v)
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_REG
p.From.Reg = r
p.To.Type = obj.TYPE_REG
p.To.Reg = r
case ssa.OpAMD64LEAQ1, ssa.OpAMD64LEAQ2, ssa.OpAMD64LEAQ4, ssa.OpAMD64LEAQ8:
p := Prog(x86.ALEAQ)
p.From.Type = obj.TYPE_MEM
p.From.Reg = regnum(v.Args[0])
switch v.Op {
case ssa.OpAMD64LEAQ1:
p.From.Scale = 1
case ssa.OpAMD64LEAQ2:
p.From.Scale = 2
case ssa.OpAMD64LEAQ4:
p.From.Scale = 4
case ssa.OpAMD64LEAQ8:
p.From.Scale = 8
}
p.From.Index = regnum(v.Args[1])
addAux(&p.From, v)
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
case ssa.OpAMD64LEAQ:
p := Prog(x86.ALEAQ)
p.From.Type = obj.TYPE_MEM
p.From.Reg = regnum(v.Args[0])
addAux(&p.From, v)
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
case ssa.OpAMD64CMPQ, ssa.OpAMD64CMPL, ssa.OpAMD64CMPW, ssa.OpAMD64CMPB,
ssa.OpAMD64TESTQ, ssa.OpAMD64TESTL, ssa.OpAMD64TESTW, ssa.OpAMD64TESTB:
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_REG
p.From.Reg = regnum(v.Args[0])
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v.Args[1])
case ssa.OpAMD64CMPQconst, ssa.OpAMD64CMPLconst, ssa.OpAMD64CMPWconst, ssa.OpAMD64CMPBconst,
ssa.OpAMD64TESTQconst, ssa.OpAMD64TESTLconst, ssa.OpAMD64TESTWconst, ssa.OpAMD64TESTBconst:
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_REG
p.From.Reg = regnum(v.Args[0])
p.To.Type = obj.TYPE_CONST
p.To.Offset = v.AuxInt
case ssa.OpAMD64MOVBconst, ssa.OpAMD64MOVWconst, ssa.OpAMD64MOVLconst, ssa.OpAMD64MOVQconst:
x := regnum(v)
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_CONST
var i int64
switch v.Op {
case ssa.OpAMD64MOVBconst:
i = int64(int8(v.AuxInt))
case ssa.OpAMD64MOVWconst:
i = int64(int16(v.AuxInt))
case ssa.OpAMD64MOVLconst:
i = int64(int32(v.AuxInt))
case ssa.OpAMD64MOVQconst:
i = v.AuxInt
}
p.From.Offset = i
p.To.Type = obj.TYPE_REG
p.To.Reg = x
case ssa.OpAMD64MOVQload, ssa.OpAMD64MOVLload, ssa.OpAMD64MOVWload, ssa.OpAMD64MOVBload, ssa.OpAMD64MOVBQSXload, ssa.OpAMD64MOVBQZXload:
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_MEM
p.From.Reg = regnum(v.Args[0])
addAux(&p.From, v)
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
case ssa.OpAMD64MOVQloadidx8:
p := Prog(x86.AMOVQ)
p.From.Type = obj.TYPE_MEM
p.From.Reg = regnum(v.Args[0])
addAux(&p.From, v)
p.From.Scale = 8
p.From.Index = regnum(v.Args[1])
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
case ssa.OpAMD64MOVQstore, ssa.OpAMD64MOVLstore, ssa.OpAMD64MOVWstore, ssa.OpAMD64MOVBstore:
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_REG
p.From.Reg = regnum(v.Args[1])
p.To.Type = obj.TYPE_MEM
p.To.Reg = regnum(v.Args[0])
addAux(&p.To, v)
case ssa.OpAMD64MOVQstoreidx8:
p := Prog(x86.AMOVQ)
p.From.Type = obj.TYPE_REG
p.From.Reg = regnum(v.Args[2])
p.To.Type = obj.TYPE_MEM
p.To.Reg = regnum(v.Args[0])
p.To.Scale = 8
p.To.Index = regnum(v.Args[1])
addAux(&p.To, v)
case ssa.OpAMD64MOVLQSX, ssa.OpAMD64MOVWQSX, ssa.OpAMD64MOVBQSX, ssa.OpAMD64MOVLQZX, ssa.OpAMD64MOVWQZX, ssa.OpAMD64MOVBQZX:
p := Prog(v.Op.Asm())
p.From.Type = obj.TYPE_REG
p.From.Reg = regnum(v.Args[0])
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
case ssa.OpAMD64MOVXzero:
nb := v.AuxInt
offset := int64(0)
reg := regnum(v.Args[0])
for nb >= 8 {
nb, offset = movZero(x86.AMOVQ, 8, nb, offset, reg)
}
for nb >= 4 {
nb, offset = movZero(x86.AMOVL, 4, nb, offset, reg)
}
for nb >= 2 {
nb, offset = movZero(x86.AMOVW, 2, nb, offset, reg)
}
for nb >= 1 {
nb, offset = movZero(x86.AMOVB, 1, nb, offset, reg)
}
case ssa.OpCopy: // TODO: lower to MOVQ earlier?
if v.Type.IsMemory() {
return
}
x := regnum(v.Args[0])
y := regnum(v)
if x != y {
p := Prog(x86.AMOVQ)
p.From.Type = obj.TYPE_REG
p.From.Reg = x
p.To.Type = obj.TYPE_REG
p.To.Reg = y
}
case ssa.OpLoadReg:
if v.Type.IsFlags() {
v.Unimplementedf("load flags not implemented: %v", v.LongString())
return
}
p := Prog(movSize(v.Type.Size()))
p.From.Type = obj.TYPE_MEM
p.From.Reg = x86.REG_SP
p.From.Offset = localOffset(v.Args[0])
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
case ssa.OpStoreReg:
if v.Type.IsFlags() {
v.Unimplementedf("store flags not implemented: %v", v.LongString())
return
}
p := Prog(movSize(v.Type.Size()))
p.From.Type = obj.TYPE_REG
p.From.Reg = regnum(v.Args[0])
p.To.Type = obj.TYPE_MEM
p.To.Reg = x86.REG_SP
p.To.Offset = localOffset(v)
case ssa.OpPhi:
// just check to make sure regalloc did it right
f := v.Block.Func
loc := f.RegAlloc[v.ID]
for _, a := range v.Args {
if aloc := f.RegAlloc[a.ID]; aloc != loc { // TODO: .Equal() instead?
v.Fatalf("phi arg at different location than phi: %v @ %v, but arg %v @ %v\n%s\n", v, loc, a, aloc, v.Block.Func)
}
}
case ssa.OpConst8, ssa.OpConst16, ssa.OpConst32, ssa.OpConst64, ssa.OpConstString, ssa.OpConstNil, ssa.OpConstBool:
if v.Block.Func.RegAlloc[v.ID] != nil {
v.Fatalf("const value %v shouldn't have a location", v)
}
case ssa.OpArg:
// memory arg needs no code
// TODO: check that only mem arg goes here.
case ssa.OpAMD64LoweredPanicNilCheck:
if Debug_checknil != 0 && v.Line > 1 { // v.Line==1 in generated wrappers
Warnl(int(v.Line), "generated nil check")
}
// Write to memory address 0. It doesn't matter what we write; use AX.
// XORL AX, AX; MOVL AX, (AX) is shorter than MOVL AX, 0.
// TODO: If we had the pointer (v.Args[0]) in a register r,
// we could use MOVL AX, (r) instead of having to zero AX.
// But it isn't worth loading r just to accomplish that.
p := Prog(x86.AXORL)
p.From.Type = obj.TYPE_REG
p.From.Reg = x86.REG_AX
p.To.Type = obj.TYPE_REG
p.To.Reg = x86.REG_AX
q := Prog(x86.AMOVL)
q.From.Type = obj.TYPE_REG
q.From.Reg = x86.REG_AX
q.To.Type = obj.TYPE_MEM
q.To.Reg = x86.REG_AX
case ssa.OpAMD64LoweredGetG:
r := regnum(v)
// See the comments in cmd/internal/obj/x86/obj6.go
// near CanUse1InsnTLS for a detailed explanation of these instructions.
if x86.CanUse1InsnTLS(Ctxt) {
// MOVQ (TLS), r
p := Prog(x86.AMOVQ)
p.From.Type = obj.TYPE_MEM
p.From.Reg = x86.REG_TLS
p.To.Type = obj.TYPE_REG
p.To.Reg = r
} else {
// MOVQ TLS, r
// MOVQ (r)(TLS*1), r
p := Prog(x86.AMOVQ)
p.From.Type = obj.TYPE_REG
p.From.Reg = x86.REG_TLS
p.To.Type = obj.TYPE_REG
p.To.Reg = r
q := Prog(x86.AMOVQ)
q.From.Type = obj.TYPE_MEM
q.From.Reg = r
q.From.Index = x86.REG_TLS
q.From.Scale = 1
q.To.Type = obj.TYPE_REG
q.To.Reg = r
}
case ssa.OpAMD64CALLstatic:
p := Prog(obj.ACALL)
p.To.Type = obj.TYPE_MEM
p.To.Name = obj.NAME_EXTERN
p.To.Sym = Linksym(v.Aux.(*Sym))
case ssa.OpAMD64CALLclosure:
p := Prog(obj.ACALL)
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v.Args[0])
case ssa.OpAMD64NEGQ, ssa.OpAMD64NEGL, ssa.OpAMD64NEGW, ssa.OpAMD64NEGB,
ssa.OpAMD64NOTQ, ssa.OpAMD64NOTL, ssa.OpAMD64NOTW, ssa.OpAMD64NOTB:
x := regnum(v.Args[0])
r := regnum(v)
if x != r {
p := Prog(regMoveAMD64(v.Type.Size()))
p.From.Type = obj.TYPE_REG
p.From.Reg = x
p.To.Type = obj.TYPE_REG
p.To.Reg = r
}
p := Prog(v.Op.Asm())
p.To.Type = obj.TYPE_REG
p.To.Reg = r
case ssa.OpSP, ssa.OpSB:
// nothing to do
case ssa.OpAMD64SETEQ, ssa.OpAMD64SETNE,
ssa.OpAMD64SETL, ssa.OpAMD64SETLE,
ssa.OpAMD64SETG, ssa.OpAMD64SETGE,
ssa.OpAMD64SETB, ssa.OpAMD64SETBE,
ssa.OpAMD64SETA, ssa.OpAMD64SETAE:
p := Prog(v.Op.Asm())
p.To.Type = obj.TYPE_REG
p.To.Reg = regnum(v)
case ssa.OpAMD64InvertFlags:
v.Fatalf("InvertFlags should never make it to codegen %v", v)
case ssa.OpAMD64REPSTOSQ:
Prog(x86.AREP)
Prog(x86.ASTOSQ)
v.Unimplementedf("REPSTOSQ clobbers not implemented: %s", v.LongString())
case ssa.OpAMD64REPMOVSB:
Prog(x86.AREP)
Prog(x86.AMOVSB)
v.Unimplementedf("REPMOVSB clobbers not implemented: %s", v.LongString())
default:
v.Unimplementedf("genValue not implemented: %s", v.LongString())
}
}
// movSize returns the MOV instruction of the given width.
func movSize(width int64) (asm int) {
switch width {
case 1:
asm = x86.AMOVB
case 2:
asm = x86.AMOVW
case 4:
asm = x86.AMOVL
case 8:
asm = x86.AMOVQ
default:
panic(fmt.Errorf("bad movSize %d", width))
}
return asm
}
// movZero generates a register indirect move with a 0 immediate and keeps track of bytes left and next offset
func movZero(as int, width int64, nbytes int64, offset int64, regnum int16) (nleft int64, noff int64) {
p := Prog(as)
// TODO: use zero register on archs that support it.
p.From.Type = obj.TYPE_CONST
p.From.Offset = 0
p.To.Type = obj.TYPE_MEM
p.To.Reg = regnum
p.To.Offset = offset
offset += width
nleft = nbytes - width
return nleft, offset
}
var blockJump = [...]struct{ asm, invasm int }{
ssa.BlockAMD64EQ: {x86.AJEQ, x86.AJNE},
ssa.BlockAMD64NE: {x86.AJNE, x86.AJEQ},
ssa.BlockAMD64LT: {x86.AJLT, x86.AJGE},
ssa.BlockAMD64GE: {x86.AJGE, x86.AJLT},
ssa.BlockAMD64LE: {x86.AJLE, x86.AJGT},
ssa.BlockAMD64GT: {x86.AJGT, x86.AJLE},
ssa.BlockAMD64ULT: {x86.AJCS, x86.AJCC},
ssa.BlockAMD64UGE: {x86.AJCC, x86.AJCS},
ssa.BlockAMD64UGT: {x86.AJHI, x86.AJLS},
ssa.BlockAMD64ULE: {x86.AJLS, x86.AJHI},
}
func genBlock(b, next *ssa.Block, branches []branch) []branch {
lineno = b.Line
switch b.Kind {
case ssa.BlockPlain:
if b.Succs[0] != next {
p := Prog(obj.AJMP)
p.To.Type = obj.TYPE_BRANCH
branches = append(branches, branch{p, b.Succs[0]})
}
case ssa.BlockExit:
Prog(obj.ARET)
case ssa.BlockCall:
if b.Succs[0] != next {
p := Prog(obj.AJMP)
p.To.Type = obj.TYPE_BRANCH
branches = append(branches, branch{p, b.Succs[0]})
}
case ssa.BlockAMD64EQ, ssa.BlockAMD64NE,
ssa.BlockAMD64LT, ssa.BlockAMD64GE,
ssa.BlockAMD64LE, ssa.BlockAMD64GT,
ssa.BlockAMD64ULT, ssa.BlockAMD64UGT,
ssa.BlockAMD64ULE, ssa.BlockAMD64UGE:
jmp := blockJump[b.Kind]
likely := b.Likely
var p *obj.Prog
switch next {
case b.Succs[0]:
p = Prog(jmp.invasm)
likely *= -1
p.To.Type = obj.TYPE_BRANCH
branches = append(branches, branch{p, b.Succs[1]})
case b.Succs[1]:
p = Prog(jmp.asm)
p.To.Type = obj.TYPE_BRANCH
branches = append(branches, branch{p, b.Succs[0]})
default:
p = Prog(jmp.asm)
p.To.Type = obj.TYPE_BRANCH
branches = append(branches, branch{p, b.Succs[0]})
q := Prog(obj.AJMP)
q.To.Type = obj.TYPE_BRANCH
branches = append(branches, branch{q, b.Succs[1]})
}
// liblink reorders the instruction stream as it sees fit.
// Pass along what we know so liblink can make use of it.
// TODO: Once we've fully switched to SSA,
// make liblink leave our output alone.
switch likely {
case ssa.BranchUnlikely:
p.From.Type = obj.TYPE_CONST
p.From.Offset = 0
case ssa.BranchLikely:
p.From.Type = obj.TYPE_CONST
p.From.Offset = 1
}
default:
b.Unimplementedf("branch not implemented: %s. Control: %s", b.LongString(), b.Control.LongString())
}
return branches
}
// addAux adds the offset in the aux fields (AuxInt and Aux) of v to a.
func addAux(a *obj.Addr, v *ssa.Value) {
if a.Type != obj.TYPE_MEM {
v.Fatalf("bad addAux addr %s", a)
}
// add integer offset
a.Offset += v.AuxInt
// If no additional symbol offset, we're done.
if v.Aux == nil {
return
}
// Add symbol's offset from its base register.
switch sym := v.Aux.(type) {
case *ssa.ExternSymbol:
a.Name = obj.NAME_EXTERN
a.Sym = Linksym(sym.Sym.(*Sym))
case *ssa.ArgSymbol:
a.Offset += v.Block.Func.FrameSize + sym.Offset
case *ssa.AutoSymbol:
if sym.Offset == -1 {
v.Fatalf("auto symbol %s offset not calculated", sym.Sym)
}
a.Offset += sym.Offset
default:
v.Fatalf("aux in %s not implemented %#v", v, v.Aux)
}
}
// extendIndex extends v to a full pointer width.
func (s *state) extendIndex(v *ssa.Value) *ssa.Value {
size := v.Type.Size()
if size == s.config.PtrSize {
return v
}
if size > s.config.PtrSize {
// TODO: truncate 64-bit indexes on 32-bit pointer archs. We'd need to test
// the high word and branch to out-of-bounds failure if it is not 0.
s.Unimplementedf("64->32 index truncation not implemented")
return v
}
// Extend value to the required size
var op ssa.Op
if v.Type.IsSigned() {
switch 10*size + s.config.PtrSize {
case 14:
op = ssa.OpSignExt8to32
case 18:
op = ssa.OpSignExt8to64
case 24:
op = ssa.OpSignExt16to32
case 28:
op = ssa.OpSignExt16to64
case 48:
op = ssa.OpSignExt32to64
default:
s.Fatalf("bad signed index extension %s", v.Type)
}
} else {
switch 10*size + s.config.PtrSize {
case 14:
op = ssa.OpZeroExt8to32
case 18:
op = ssa.OpZeroExt8to64
case 24:
op = ssa.OpZeroExt16to32
case 28:
op = ssa.OpZeroExt16to64
case 48:
op = ssa.OpZeroExt32to64
default:
s.Fatalf("bad unsigned index extension %s", v.Type)
}
}
return s.newValue1(op, Types[TUINTPTR], v)
}
// ssaRegToReg maps ssa register numbers to obj register numbers.
var ssaRegToReg = [...]int16{
x86.REG_AX,
x86.REG_CX,
x86.REG_DX,
x86.REG_BX,
x86.REG_SP,
x86.REG_BP,
x86.REG_SI,
x86.REG_DI,
x86.REG_R8,
x86.REG_R9,
x86.REG_R10,
x86.REG_R11,
x86.REG_R12,
x86.REG_R13,
x86.REG_R14,
x86.REG_R15,
x86.REG_X0,
x86.REG_X1,
x86.REG_X2,
x86.REG_X3,
x86.REG_X4,
x86.REG_X5,
x86.REG_X6,
x86.REG_X7,
x86.REG_X8,
x86.REG_X9,
x86.REG_X10,
x86.REG_X11,
x86.REG_X12,
x86.REG_X13,
x86.REG_X14,
x86.REG_X15,
0, // SB isn't a real register. We fill an Addr.Reg field with 0 in this case.
// TODO: arch-dependent
}
// regMoveAMD64 returns the register->register move opcode for the given width.
// TODO: generalize for all architectures?
func regMoveAMD64(width int64) int {
switch width {
case 1:
return x86.AMOVB
case 2:
return x86.AMOVW
case 4:
return x86.AMOVL
case 8:
return x86.AMOVQ
default:
panic("bad register width")
}
}
// regnum returns the register (in cmd/internal/obj numbering) to
// which v has been allocated. Panics if v is not assigned to a
// register.
// TODO: Make this panic again once it stops happening routinely.
func regnum(v *ssa.Value) int16 {
reg := v.Block.Func.RegAlloc[v.ID]
if reg == nil {
v.Unimplementedf("nil regnum for value: %s\n%s\n", v.LongString(), v.Block.Func)
return 0
}
return ssaRegToReg[reg.(*ssa.Register).Num]
}
// localOffset returns the offset below the frame pointer where
// a stack-allocated local has been allocated. Panics if v
// is not assigned to a local slot.
// TODO: Make this panic again once it stops happening routinely.
func localOffset(v *ssa.Value) int64 {
reg := v.Block.Func.RegAlloc[v.ID]
slot, ok := reg.(*ssa.LocalSlot)
if !ok {
v.Unimplementedf("localOffset of non-LocalSlot value: %s\n%s\n", v.LongString(), v.Block.Func)
return 0
}
return slot.Idx
}
// ssaExport exports a bunch of compiler services for the ssa backend.
type ssaExport struct {
log bool
unimplemented bool
mustImplement bool
}
func (s *ssaExport) TypeBool() ssa.Type { return Types[TBOOL] }
func (s *ssaExport) TypeInt8() ssa.Type { return Types[TINT8] }
func (s *ssaExport) TypeInt16() ssa.Type { return Types[TINT16] }
func (s *ssaExport) TypeInt32() ssa.Type { return Types[TINT32] }
func (s *ssaExport) TypeInt64() ssa.Type { return Types[TINT64] }
func (s *ssaExport) TypeUInt8() ssa.Type { return Types[TUINT8] }
func (s *ssaExport) TypeUInt16() ssa.Type { return Types[TUINT16] }
func (s *ssaExport) TypeUInt32() ssa.Type { return Types[TUINT32] }
func (s *ssaExport) TypeUInt64() ssa.Type { return Types[TUINT64] }
func (s *ssaExport) TypeInt() ssa.Type { return Types[TINT] }
func (s *ssaExport) TypeUintptr() ssa.Type { return Types[TUINTPTR] }
func (s *ssaExport) TypeString() ssa.Type { return Types[TSTRING] }
func (s *ssaExport) TypeBytePtr() ssa.Type { return Ptrto(Types[TUINT8]) }
// StringData returns a symbol (a *Sym wrapped in an interface) which
// is the data component of a global string constant containing s.
func (*ssaExport) StringData(s string) interface{} {
// TODO: is idealstring correct? It might not matter...
_, data := stringsym(s)
return &ssa.ExternSymbol{Typ: idealstring, Sym: data}
}
// Log logs a message from the compiler.
func (e *ssaExport) Logf(msg string, args ...interface{}) {
// If e was marked as unimplemented, anything could happen. Ignore.
if e.log && !e.unimplemented {
fmt.Printf(msg, args...)
}
}
// Fatal reports a compiler error and exits.
func (e *ssaExport) Fatalf(msg string, args ...interface{}) {
// If e was marked as unimplemented, anything could happen. Ignore.
if !e.unimplemented {
Fatal(msg, args...)
}
}
// Unimplemented reports that the function cannot be compiled.
// It will be removed once SSA work is complete.
func (e *ssaExport) Unimplementedf(msg string, args ...interface{}) {
if e.mustImplement {
Fatal(msg, args...)
}
const alwaysLog = false // enable to calculate top unimplemented features
if !e.unimplemented && (e.log || alwaysLog) {
// first implementation failure, print explanation
fmt.Printf("SSA unimplemented: "+msg+"\n", args...)
}
e.unimplemented = true
}