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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 ssa
import (
// An Op encodes the specific operation that a Value performs.
// Opcodes' semantics can be modified by the type and aux fields of the Value.
// For instance, OpAdd can be 32 or 64 bit, signed or unsigned, float or complex, depending on Value.Type.
// Semantics of each op are described in the opcode files in gen/*Ops.go.
// There is one file for generic (architecture-independent) ops and one file
// for each architecture.
type Op int32
type opInfo struct {
name string
reg regInfo
auxType auxType
argLen int32 // the number of arguments, -1 if variable length
asm obj.As
generic bool // this is a generic (arch-independent) opcode
rematerializeable bool // this op is rematerializeable
commutative bool // this operation is commutative (e.g. addition)
resultInArg0 bool // (first, if a tuple) output of v and v.Args[0] must be allocated to the same register
resultNotInArgs bool // outputs must not be allocated to the same registers as inputs
clobberFlags bool // this op clobbers flags register
call bool // is a function call
nilCheck bool // this op is a nil check on arg0
faultOnNilArg0 bool // this op will fault if arg0 is nil (and aux encodes a small offset)
faultOnNilArg1 bool // this op will fault if arg1 is nil (and aux encodes a small offset)
usesScratch bool // this op requires scratch memory space
hasSideEffects bool // for "reasons", not to be eliminated. E.g., atomic store, #19182.
zeroWidth bool // op never translates into any machine code. example: copy, which may sometimes translate to machine code, is not zero-width.
unsafePoint bool // this op is an unsafe point, i.e. not safe for async preemption
symEffect SymEffect // effect this op has on symbol in aux
scale uint8 // amd64/386 indexed load scale
type inputInfo struct {
idx int // index in Args array
regs regMask // allowed input registers
type outputInfo struct {
idx int // index in output tuple
regs regMask // allowed output registers
type regInfo struct {
// inputs encodes the register restrictions for an instruction's inputs.
// Each entry specifies an allowed register set for a particular input.
// They are listed in the order in which regalloc should pick a register
// from the register set (most constrained first).
// Inputs which do not need registers are not listed.
inputs []inputInfo
// clobbers encodes the set of registers that are overwritten by
// the instruction (other than the output registers).
clobbers regMask
// outputs is the same as inputs, but for the outputs of the instruction.
outputs []outputInfo
type auxType int8
const (
auxNone auxType = iota
auxBool // auxInt is 0/1 for false/true
auxInt8 // auxInt is an 8-bit integer
auxInt16 // auxInt is a 16-bit integer
auxInt32 // auxInt is a 32-bit integer
auxInt64 // auxInt is a 64-bit integer
auxInt128 // auxInt represents a 128-bit integer. Always 0.
auxFloat32 // auxInt is a float32 (encoded with math.Float64bits)
auxFloat64 // auxInt is a float64 (encoded with math.Float64bits)
auxFlagConstant // auxInt is a flagConstant
auxString // aux is a string
auxSym // aux is a symbol (a *gc.Node for locals, an *obj.LSym for globals, or nil for none)
auxSymOff // aux is a symbol, auxInt is an offset
auxSymValAndOff // aux is a symbol, auxInt is a ValAndOff
auxTyp // aux is a type
auxTypSize // aux is a type, auxInt is a size, must have Aux.(Type).Size() == AuxInt
auxCCop // aux is a ssa.Op that represents a flags-to-bool conversion (e.g. LessThan)
// architecture specific aux types
auxARM64BitField // aux is an arm64 bitfield lsb and width packed into auxInt
auxS390XRotateParams // aux is a s390x rotate parameters object encoding start bit, end bit and rotate amount
auxS390XCCMask // aux is a s390x 4-bit condition code mask
auxS390XCCMaskInt8 // aux is a s390x 4-bit condition code mask, auxInt is a int8 immediate
auxS390XCCMaskUint8 // aux is a s390x 4-bit condition code mask, auxInt is a uint8 immediate
// A SymEffect describes the effect that an SSA Value has on the variable
// identified by the symbol in its Aux field.
type SymEffect int8
const (
SymRead SymEffect = 1 << iota
SymRdWr = SymRead | SymWrite
SymNone SymEffect = 0
// A Sym represents a symbolic offset from a base register.
// Currently a Sym can be one of 3 things:
// - a *gc.Node, for an offset from SP (the stack pointer)
// - a *obj.LSym, for an offset from SB (the global pointer)
// - nil, for no offset
type Sym interface {
String() string
// A ValAndOff is used by the several opcodes. It holds
// both a value and a pointer offset.
// A ValAndOff is intended to be encoded into an AuxInt field.
// The zero ValAndOff encodes a value of 0 and an offset of 0.
// The high 32 bits hold a value.
// The low 32 bits hold a pointer offset.
type ValAndOff int64
func (x ValAndOff) Val() int64 { return int64(x) >> 32 }
func (x ValAndOff) Val32() int32 { return int32(int64(x) >> 32) }
func (x ValAndOff) Val16() int16 { return int16(int64(x) >> 32) }
func (x ValAndOff) Val8() int8 { return int8(int64(x) >> 32) }
func (x ValAndOff) Off() int64 { return int64(int32(x)) }
func (x ValAndOff) Off32() int32 { return int32(x) }
func (x ValAndOff) Int64() int64 {
return int64(x)
func (x ValAndOff) String() string {
return fmt.Sprintf("val=%d,off=%d", x.Val(), x.Off())
// validVal reports whether the value can be used
// as an argument to makeValAndOff.
func validVal(val int64) bool {
return val == int64(int32(val))
// validOff reports whether the offset can be used
// as an argument to makeValAndOff.
func validOff(off int64) bool {
return off == int64(int32(off))
// validValAndOff reports whether we can fit the value and offset into
// a ValAndOff value.
func validValAndOff(val, off int64) bool {
if !validVal(val) {
return false
if !validOff(off) {
return false
return true
// makeValAndOff encodes a ValAndOff into an int64 suitable for storing in an AuxInt field.
func makeValAndOff(val, off int64) int64 {
if !validValAndOff(val, off) {
panic("invalid makeValAndOff")
return ValAndOff(val<<32 + int64(uint32(off))).Int64()
func makeValAndOff32(val, off int32) ValAndOff {
return ValAndOff(int64(val)<<32 + int64(uint32(off)))
func (x ValAndOff) canAdd(off int64) bool {
newoff := x.Off() + off
return newoff == int64(int32(newoff))
func (x ValAndOff) canAdd32(off int32) bool {
newoff := x.Off() + int64(off)
return newoff == int64(int32(newoff))
func (x ValAndOff) add(off int64) int64 {
if !x.canAdd(off) {
panic("invalid ValAndOff.add")
return makeValAndOff(x.Val(), x.Off()+off)
func (x ValAndOff) addOffset32(off int32) ValAndOff {
if !x.canAdd32(off) {
panic("invalid ValAndOff.add")
return ValAndOff(makeValAndOff(x.Val(), x.Off()+int64(off)))
func (x ValAndOff) addOffset64(off int64) ValAndOff {
if !x.canAdd(off) {
panic("invalid ValAndOff.add")
return ValAndOff(makeValAndOff(x.Val(), x.Off()+off))
// int128 is a type that stores a 128-bit constant.
// The only allowed constant right now is 0, so we can cheat quite a bit.
type int128 int64
type BoundsKind uint8
const (
BoundsIndex BoundsKind = iota // indexing operation, 0 <= idx < len failed
BoundsIndexU // ... with unsigned idx
BoundsSliceAlen // 2-arg slicing operation, 0 <= high <= len failed
BoundsSliceAlenU // ... with unsigned high
BoundsSliceAcap // 2-arg slicing operation, 0 <= high <= cap failed
BoundsSliceAcapU // ... with unsigned high
BoundsSliceB // 2-arg slicing operation, 0 <= low <= high failed
BoundsSliceBU // ... with unsigned low
BoundsSlice3Alen // 3-arg slicing operation, 0 <= max <= len failed
BoundsSlice3AlenU // ... with unsigned max
BoundsSlice3Acap // 3-arg slicing operation, 0 <= max <= cap failed
BoundsSlice3AcapU // ... with unsigned max
BoundsSlice3B // 3-arg slicing operation, 0 <= high <= max failed
BoundsSlice3BU // ... with unsigned high
BoundsSlice3C // 3-arg slicing operation, 0 <= low <= high failed
BoundsSlice3CU // ... with unsigned low
// boundsAPI determines which register arguments a bounds check call should use. For an [a:b:c] slice, we do:
// CMPQ c, cap
// JA fail1
// CMPQ b, c
// JA fail2
// CMPQ a, b
// JA fail3
// fail1: CALL panicSlice3Acap (c, cap)
// fail2: CALL panicSlice3B (b, c)
// fail3: CALL panicSlice3C (a, b)
// When we register allocate that code, we want the same register to be used for
// the first arg of panicSlice3Acap and the second arg to panicSlice3B. That way,
// initializing that register once will satisfy both calls.
// That desire ends up dividing the set of bounds check calls into 3 sets. This function
// determines which set to use for a given panic call.
// The first arg for set 0 should be the second arg for set 1.
// The first arg for set 1 should be the second arg for set 2.
func boundsABI(b int64) int {
switch BoundsKind(b) {
case BoundsSlice3Alen,
return 0
case BoundsSliceAlen,
return 1
case BoundsIndex,
return 2
panic("bad BoundsKind")
// arm64BitFileld is the GO type of ARM64BitField auxInt.
// if x is an ARM64BitField, then width=x&0xff, lsb=(x>>8)&0xff, and
// width+lsb<64 for 64-bit variant, width+lsb<32 for 32-bit variant.
// the meaning of width and lsb are instruction-dependent.
type arm64BitField int16