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// Copyright 2013 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 obj
import (
"cmd/internal/goobj"
"encoding/binary"
"log"
)
// funcpctab writes to dst a pc-value table mapping the code in func to the values
// returned by valfunc parameterized by arg. The invocation of valfunc to update the
// current value is, for each p,
//
// val = valfunc(func, val, p, 0, arg);
// record val as value at p->pc;
// val = valfunc(func, val, p, 1, arg);
//
// where func is the function, val is the current value, p is the instruction being
// considered, and arg can be used to further parameterize valfunc.
func funcpctab(ctxt *Link, dst *Pcdata, func_ *LSym, desc string, valfunc func(*Link, *LSym, int32, *Prog, int32, interface{}) int32, arg interface{}) {
dbg := desc == ctxt.Debugpcln
dst.P = dst.P[:0]
if dbg {
ctxt.Logf("funcpctab %s [valfunc=%s]\n", func_.Name, desc)
}
val := int32(-1)
oldval := val
if func_.Func.Text == nil {
return
}
pc := func_.Func.Text.Pc
if dbg {
ctxt.Logf("%6x %6d %v\n", uint64(pc), val, func_.Func.Text)
}
buf := make([]byte, binary.MaxVarintLen32)
started := false
for p := func_.Func.Text; p != nil; p = p.Link {
// Update val. If it's not changing, keep going.
val = valfunc(ctxt, func_, val, p, 0, arg)
if val == oldval && started {
val = valfunc(ctxt, func_, val, p, 1, arg)
if dbg {
ctxt.Logf("%6x %6s %v\n", uint64(p.Pc), "", p)
}
continue
}
// If the pc of the next instruction is the same as the
// pc of this instruction, this instruction is not a real
// instruction. Keep going, so that we only emit a delta
// for a true instruction boundary in the program.
if p.Link != nil && p.Link.Pc == p.Pc {
val = valfunc(ctxt, func_, val, p, 1, arg)
if dbg {
ctxt.Logf("%6x %6s %v\n", uint64(p.Pc), "", p)
}
continue
}
// The table is a sequence of (value, pc) pairs, where each
// pair states that the given value is in effect from the current position
// up to the given pc, which becomes the new current position.
// To generate the table as we scan over the program instructions,
// we emit a "(value" when pc == func->value, and then
// each time we observe a change in value we emit ", pc) (value".
// When the scan is over, we emit the closing ", pc)".
//
// The table is delta-encoded. The value deltas are signed and
// transmitted in zig-zag form, where a complement bit is placed in bit 0,
// and the pc deltas are unsigned. Both kinds of deltas are sent
// as variable-length little-endian base-128 integers,
// where the 0x80 bit indicates that the integer continues.
if dbg {
ctxt.Logf("%6x %6d %v\n", uint64(p.Pc), val, p)
}
if started {
pcdelta := (p.Pc - pc) / int64(ctxt.Arch.MinLC)
n := binary.PutUvarint(buf, uint64(pcdelta))
dst.P = append(dst.P, buf[:n]...)
pc = p.Pc
}
delta := val - oldval
n := binary.PutVarint(buf, int64(delta))
dst.P = append(dst.P, buf[:n]...)
oldval = val
started = true
val = valfunc(ctxt, func_, val, p, 1, arg)
}
if started {
if dbg {
ctxt.Logf("%6x done\n", uint64(func_.Func.Text.Pc+func_.Size))
}
v := (func_.Size - pc) / int64(ctxt.Arch.MinLC)
if v < 0 {
ctxt.Diag("negative pc offset: %v", v)
}
n := binary.PutUvarint(buf, uint64(v))
dst.P = append(dst.P, buf[:n]...)
// add terminating varint-encoded 0, which is just 0
dst.P = append(dst.P, 0)
}
if dbg {
ctxt.Logf("wrote %d bytes to %p\n", len(dst.P), dst)
for _, p := range dst.P {
ctxt.Logf(" %02x", p)
}
ctxt.Logf("\n")
}
}
// pctofileline computes either the file number (arg == 0)
// or the line number (arg == 1) to use at p.
// Because p.Pos applies to p, phase == 0 (before p)
// takes care of the update.
func pctofileline(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg interface{}) int32 {
if p.As == ATEXT || p.As == ANOP || p.Pos.Line() == 0 || phase == 1 {
return oldval
}
f, l := getFileIndexAndLine(ctxt, p.Pos)
if arg == nil {
return l
}
pcln := arg.(*Pcln)
pcln.UsedFiles[goobj.CUFileIndex(f)] = struct{}{}
return int32(f)
}
// pcinlineState holds the state used to create a function's inlining
// tree and the PC-value table that maps PCs to nodes in that tree.
type pcinlineState struct {
globalToLocal map[int]int
localTree InlTree
}
// addBranch adds a branch from the global inlining tree in ctxt to
// the function's local inlining tree, returning the index in the local tree.
func (s *pcinlineState) addBranch(ctxt *Link, globalIndex int) int {
if globalIndex < 0 {
return -1
}
localIndex, ok := s.globalToLocal[globalIndex]
if ok {
return localIndex
}
// Since tracebacks don't include column information, we could
// use one node for multiple calls of the same function on the
// same line (e.g., f(x) + f(y)). For now, we use one node for
// each inlined call.
call := ctxt.InlTree.nodes[globalIndex]
call.Parent = s.addBranch(ctxt, call.Parent)
localIndex = len(s.localTree.nodes)
s.localTree.nodes = append(s.localTree.nodes, call)
s.globalToLocal[globalIndex] = localIndex
return localIndex
}
func (s *pcinlineState) setParentPC(ctxt *Link, globalIndex int, pc int32) {
localIndex, ok := s.globalToLocal[globalIndex]
if !ok {
// We know where to unwind to when we need to unwind a body identified
// by globalIndex. But there may be no instructions generated by that
// body (it's empty, or its instructions were CSEd with other things, etc.).
// In that case, we don't need an unwind entry.
// TODO: is this really right? Seems to happen a whole lot...
return
}
s.localTree.setParentPC(localIndex, pc)
}
// pctoinline computes the index into the local inlining tree to use at p.
// If p is not the result of inlining, pctoinline returns -1. Because p.Pos
// applies to p, phase == 0 (before p) takes care of the update.
func (s *pcinlineState) pctoinline(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg interface{}) int32 {
if phase == 1 {
return oldval
}
posBase := ctxt.PosTable.Pos(p.Pos).Base()
if posBase == nil {
return -1
}
globalIndex := posBase.InliningIndex()
if globalIndex < 0 {
return -1
}
if s.globalToLocal == nil {
s.globalToLocal = make(map[int]int)
}
return int32(s.addBranch(ctxt, globalIndex))
}
// pctospadj computes the sp adjustment in effect.
// It is oldval plus any adjustment made by p itself.
// The adjustment by p takes effect only after p, so we
// apply the change during phase == 1.
func pctospadj(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg interface{}) int32 {
if oldval == -1 { // starting
oldval = 0
}
if phase == 0 {
return oldval
}
if oldval+p.Spadj < -10000 || oldval+p.Spadj > 1100000000 {
ctxt.Diag("overflow in spadj: %d + %d = %d", oldval, p.Spadj, oldval+p.Spadj)
ctxt.DiagFlush()
log.Fatalf("bad code")
}
return oldval + p.Spadj
}
// pctopcdata computes the pcdata value in effect at p.
// A PCDATA instruction sets the value in effect at future
// non-PCDATA instructions.
// Since PCDATA instructions have no width in the final code,
// it does not matter which phase we use for the update.
func pctopcdata(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg interface{}) int32 {
if phase == 0 || p.As != APCDATA || p.From.Offset != int64(arg.(uint32)) {
return oldval
}
if int64(int32(p.To.Offset)) != p.To.Offset {
ctxt.Diag("overflow in PCDATA instruction: %v", p)
ctxt.DiagFlush()
log.Fatalf("bad code")
}
return int32(p.To.Offset)
}
func linkpcln(ctxt *Link, cursym *LSym) {
pcln := &cursym.Func.Pcln
pcln.UsedFiles = make(map[goobj.CUFileIndex]struct{})
npcdata := 0
nfuncdata := 0
for p := cursym.Func.Text; p != nil; p = p.Link {
// Find the highest ID of any used PCDATA table. This ignores PCDATA table
// that consist entirely of "-1", since that's the assumed default value.
// From.Offset is table ID
// To.Offset is data
if p.As == APCDATA && p.From.Offset >= int64(npcdata) && p.To.Offset != -1 { // ignore -1 as we start at -1, if we only see -1, nothing changed
npcdata = int(p.From.Offset + 1)
}
// Find the highest ID of any FUNCDATA table.
// From.Offset is table ID
if p.As == AFUNCDATA && p.From.Offset >= int64(nfuncdata) {
nfuncdata = int(p.From.Offset + 1)
}
}
pcln.Pcdata = make([]Pcdata, npcdata)
pcln.Pcdata = pcln.Pcdata[:npcdata]
pcln.Funcdata = make([]*LSym, nfuncdata)
pcln.Funcdataoff = make([]int64, nfuncdata)
pcln.Funcdataoff = pcln.Funcdataoff[:nfuncdata]
funcpctab(ctxt, &pcln.Pcsp, cursym, "pctospadj", pctospadj, nil)
funcpctab(ctxt, &pcln.Pcfile, cursym, "pctofile", pctofileline, pcln)
funcpctab(ctxt, &pcln.Pcline, cursym, "pctoline", pctofileline, nil)
// Check that all the Progs used as inline markers are still reachable.
// See issue #40473.
inlMarkProgs := make(map[*Prog]struct{}, len(cursym.Func.InlMarks))
for _, inlMark := range cursym.Func.InlMarks {
inlMarkProgs[inlMark.p] = struct{}{}
}
for p := cursym.Func.Text; p != nil; p = p.Link {
if _, ok := inlMarkProgs[p]; ok {
delete(inlMarkProgs, p)
}
}
if len(inlMarkProgs) > 0 {
ctxt.Diag("one or more instructions used as inline markers are no longer reachable")
}
pcinlineState := new(pcinlineState)
funcpctab(ctxt, &pcln.Pcinline, cursym, "pctoinline", pcinlineState.pctoinline, nil)
for _, inlMark := range cursym.Func.InlMarks {
pcinlineState.setParentPC(ctxt, int(inlMark.id), int32(inlMark.p.Pc))
}
pcln.InlTree = pcinlineState.localTree
if ctxt.Debugpcln == "pctoinline" && len(pcln.InlTree.nodes) > 0 {
ctxt.Logf("-- inlining tree for %s:\n", cursym)
dumpInlTree(ctxt, pcln.InlTree)
ctxt.Logf("--\n")
}
// tabulate which pc and func data we have.
havepc := make([]uint32, (npcdata+31)/32)
havefunc := make([]uint32, (nfuncdata+31)/32)
for p := cursym.Func.Text; p != nil; p = p.Link {
if p.As == AFUNCDATA {
if (havefunc[p.From.Offset/32]>>uint64(p.From.Offset%32))&1 != 0 {
ctxt.Diag("multiple definitions for FUNCDATA $%d", p.From.Offset)
}
havefunc[p.From.Offset/32] |= 1 << uint64(p.From.Offset%32)
}
if p.As == APCDATA && p.To.Offset != -1 {
havepc[p.From.Offset/32] |= 1 << uint64(p.From.Offset%32)
}
}
// pcdata.
for i := 0; i < npcdata; i++ {
if (havepc[i/32]>>uint(i%32))&1 == 0 {
continue
}
funcpctab(ctxt, &pcln.Pcdata[i], cursym, "pctopcdata", pctopcdata, interface{}(uint32(i)))
}
// funcdata
if nfuncdata > 0 {
for p := cursym.Func.Text; p != nil; p = p.Link {
if p.As != AFUNCDATA {
continue
}
i := int(p.From.Offset)
pcln.Funcdataoff[i] = p.To.Offset
if p.To.Type != TYPE_CONST {
// TODO: Dedup.
//funcdata_bytes += p->to.sym->size;
pcln.Funcdata[i] = p.To.Sym
}
}
}
}
// PCIter iterates over encoded pcdata tables.
type PCIter struct {
p []byte
PC uint32
NextPC uint32
PCScale uint32
Value int32
start bool
Done bool
}
// newPCIter creates a PCIter with a scale factor for the PC step size.
func NewPCIter(pcScale uint32) *PCIter {
it := new(PCIter)
it.PCScale = pcScale
return it
}
// Next advances it to the Next pc.
func (it *PCIter) Next() {
it.PC = it.NextPC
if it.Done {
return
}
if len(it.p) == 0 {
it.Done = true
return
}
// Value delta
val, n := binary.Varint(it.p)
if n <= 0 {
log.Fatalf("bad Value varint in pciterNext: read %v", n)
}
it.p = it.p[n:]
if val == 0 && !it.start {
it.Done = true
return
}
it.start = false
it.Value += int32(val)
// pc delta
pc, n := binary.Uvarint(it.p)
if n <= 0 {
log.Fatalf("bad pc varint in pciterNext: read %v", n)
}
it.p = it.p[n:]
it.NextPC = it.PC + uint32(pc)*it.PCScale
}
// init prepares it to iterate over p,
// and advances it to the first pc.
func (it *PCIter) Init(p []byte) {
it.p = p
it.PC = 0
it.NextPC = 0
it.Value = -1
it.start = true
it.Done = false
it.Next()
}