src/cmd/compile/internal/ssa/op.go - go - Git at Google

 // 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 (
 	"cmd/compile/internal/abi"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"fmt"
 	"strings"
 )

 // 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
 	needIntTemp       bool      // need a temporary free integer register
 	call              bool      // is a function call
 	tailCall          bool      // is a tail 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
 }

 func (r *regInfo) String() string {
 	s := ""
 	s += "INS:\n"
 	for _, i := range r.inputs {
 		mask := fmt.Sprintf("%64b", i.regs)
 		mask = strings.Replace(mask, "0", ".", -1)
 		s += fmt.Sprintf("%2d |%s|\n", i.idx, mask)
 	}
 	s += "OUTS:\n"
 	for _, i := range r.outputs {
 		mask := fmt.Sprintf("%64b", i.regs)
 		mask = strings.Replace(mask, "0", ".", -1)
 		s += fmt.Sprintf("%2d |%s|\n", i.idx, mask)
 	}
 	s += "CLOBBERS:\n"
 	mask := fmt.Sprintf("%64b", r.clobbers)
 	mask = strings.Replace(mask, "0", ".", -1)
 	s += fmt.Sprintf("   |%s|\n", mask)
 	return s
 }

 type auxType int8

 type AuxNameOffset struct {
 	Name   *ir.Name
 	Offset int64
 }

 func (a *AuxNameOffset) CanBeAnSSAAux() {}
 func (a *AuxNameOffset) String() string {
 	return fmt.Sprintf("%s+%d", a.Name.Sym().Name, a.Offset)
 }

 func (a *AuxNameOffset) FrameOffset() int64 {
 	return a.Name.FrameOffset() + a.Offset
 }

 type AuxCall struct {
 	Fn      *obj.LSym
 	reg     *regInfo // regInfo for this call
 	abiInfo *abi.ABIParamResultInfo
 }

 // Reg returns the regInfo for a given call, combining the derived in/out register masks
 // with the machine-specific register information in the input i.  (The machine-specific
 // regInfo is much handier at the call site than it is when the AuxCall is being constructed,
 // therefore do this lazily).
 //
 // TODO: there is a Clever Hack that allows pre-generation of a small-ish number of the slices
 // of inputInfo and outputInfo used here, provided that we are willing to reorder the inputs
 // and outputs from calls, so that all integer registers come first, then all floating registers.
 // At this point (active development of register ABI) that is very premature,
 // but if this turns out to be a cost, we could do it.
 func (a *AuxCall) Reg(i *regInfo, c *Config) *regInfo {
 	if a.reg.clobbers != 0 {
 		// Already updated
 		return a.reg
 	}
 	if a.abiInfo.InRegistersUsed()+a.abiInfo.OutRegistersUsed() == 0 {
 		// Shortcut for zero case, also handles old ABI.
 		a.reg = i
 		return a.reg
 	}

 	k := len(i.inputs)
 	for _, p := range a.abiInfo.InParams() {
 		for _, r := range p.Registers {
 			m := archRegForAbiReg(r, c)
 			a.reg.inputs = append(a.reg.inputs, inputInfo{idx: k, regs: (1 << m)})
 			k++
 		}
 	}
 	a.reg.inputs = append(a.reg.inputs, i.inputs...) // These are less constrained, thus should come last
 	k = len(i.outputs)
 	for _, p := range a.abiInfo.OutParams() {
 		for _, r := range p.Registers {
 			m := archRegForAbiReg(r, c)
 			a.reg.outputs = append(a.reg.outputs, outputInfo{idx: k, regs: (1 << m)})
 			k++
 		}
 	}
 	a.reg.outputs = append(a.reg.outputs, i.outputs...)
 	a.reg.clobbers = i.clobbers
 	return a.reg
 }
 func (a *AuxCall) ABI() *abi.ABIConfig {
 	return a.abiInfo.Config()
 }
 func (a *AuxCall) ABIInfo() *abi.ABIParamResultInfo {
 	return a.abiInfo
 }
 func (a *AuxCall) ResultReg(c *Config) *regInfo {
 	if a.abiInfo.OutRegistersUsed() == 0 {
 		return a.reg
 	}
 	if len(a.reg.inputs) > 0 {
 		return a.reg
 	}
 	k := 0
 	for _, p := range a.abiInfo.OutParams() {
 		for _, r := range p.Registers {
 			m := archRegForAbiReg(r, c)
 			a.reg.inputs = append(a.reg.inputs, inputInfo{idx: k, regs: (1 << m)})
 			k++
 		}
 	}
 	return a.reg
 }

 // For ABI register index r, returns the (dense) register number used in
 // SSA backend.
 func archRegForAbiReg(r abi.RegIndex, c *Config) uint8 {
 	var m int8
 	if int(r) < len(c.intParamRegs) {
 		m = c.intParamRegs[r]
 	} else {
 		m = c.floatParamRegs[int(r)-len(c.intParamRegs)]
 	}
 	return uint8(m)
 }

 // For ABI register index r, returns the register number used in the obj
 // package (assembler).
 func ObjRegForAbiReg(r abi.RegIndex, c *Config) int16 {
 	m := archRegForAbiReg(r, c)
 	return c.registers[m].objNum
 }

 // ArgWidth returns the amount of stack needed for all the inputs
 // and outputs of a function or method, including ABI-defined parameter
 // slots and ABI-defined spill slots for register-resident parameters.
 //
 // The name is taken from the types package's ArgWidth(<function type>),
 // which predated changes to the ABI; this version handles those changes.
 func (a *AuxCall) ArgWidth() int64 {
 	return a.abiInfo.ArgWidth()
 }

 // ParamAssignmentForResult returns the ABI Parameter assignment for result which (indexed 0, 1, etc).
 func (a *AuxCall) ParamAssignmentForResult(which int64) *abi.ABIParamAssignment {
 	return a.abiInfo.OutParam(int(which))
 }

 // OffsetOfResult returns the SP offset of result which (indexed 0, 1, etc).
 func (a *AuxCall) OffsetOfResult(which int64) int64 {
 	n := int64(a.abiInfo.OutParam(int(which)).Offset())
 	return n
 }

 // OffsetOfArg returns the SP offset of argument which (indexed 0, 1, etc).
 // If the call is to a method, the receiver is the first argument (i.e., index 0)
 func (a *AuxCall) OffsetOfArg(which int64) int64 {
 	n := int64(a.abiInfo.InParam(int(which)).Offset())
 	return n
 }

 // RegsOfResult returns the register(s) used for result which (indexed 0, 1, etc).
 func (a *AuxCall) RegsOfResult(which int64) []abi.RegIndex {
 	return a.abiInfo.OutParam(int(which)).Registers
 }

 // RegsOfArg returns the register(s) used for argument which (indexed 0, 1, etc).
 // If the call is to a method, the receiver is the first argument (i.e., index 0)
 func (a *AuxCall) RegsOfArg(which int64) []abi.RegIndex {
 	return a.abiInfo.InParam(int(which)).Registers
 }

 // NameOfResult returns the type of result which (indexed 0, 1, etc).
 func (a *AuxCall) NameOfResult(which int64) *ir.Name {
 	name := a.abiInfo.OutParam(int(which)).Name
 	if name == nil {
 		return nil
 	}
 	return name.(*ir.Name)
 }

 // TypeOfResult returns the type of result which (indexed 0, 1, etc).
 func (a *AuxCall) TypeOfResult(which int64) *types.Type {
 	return a.abiInfo.OutParam(int(which)).Type
 }

 // TypeOfArg returns the type of argument which (indexed 0, 1, etc).
 // If the call is to a method, the receiver is the first argument (i.e., index 0)
 func (a *AuxCall) TypeOfArg(which int64) *types.Type {
 	return a.abiInfo.InParam(int(which)).Type
 }

 // SizeOfResult returns the size of result which (indexed 0, 1, etc).
 func (a *AuxCall) SizeOfResult(which int64) int64 {
 	return a.TypeOfResult(which).Size()
 }

 // SizeOfArg returns the size of argument which (indexed 0, 1, etc).
 // If the call is to a method, the receiver is the first argument (i.e., index 0)
 func (a *AuxCall) SizeOfArg(which int64) int64 {
 	return a.TypeOfArg(which).Size()
 }

 // NResults returns the number of results.
 func (a *AuxCall) NResults() int64 {
 	return int64(len(a.abiInfo.OutParams()))
 }

 // LateExpansionResultType returns the result type (including trailing mem)
 // for a call that will be expanded later in the SSA phase.
 func (a *AuxCall) LateExpansionResultType() *types.Type {
 	var tys []*types.Type
 	for i := int64(0); i < a.NResults(); i++ {
 		tys = append(tys, a.TypeOfResult(i))
 	}
 	tys = append(tys, types.TypeMem)
 	return types.NewResults(tys)
 }

 // NArgs returns the number of arguments (including receiver, if there is one).
 func (a *AuxCall) NArgs() int64 {
 	return int64(len(a.abiInfo.InParams()))
 }

 // String returns "AuxCall{<fn>}"
 func (a *AuxCall) String() string {
 	var fn string
 	if a.Fn == nil {
 		fn = "AuxCall{nil" // could be interface/closure etc.
 	} else {
 		fn = fmt.Sprintf("AuxCall{%v", a.Fn)
 	}
 	// TODO how much of the ABI should be printed?

 	return fn + "}"
 }

 // StaticAuxCall returns an AuxCall for a static call.
 func StaticAuxCall(sym *obj.LSym, paramResultInfo *abi.ABIParamResultInfo) *AuxCall {
 	if paramResultInfo == nil {
 		panic(fmt.Errorf("Nil paramResultInfo, sym=%v", sym))
 	}
 	var reg *regInfo
 	if paramResultInfo.InRegistersUsed()+paramResultInfo.OutRegistersUsed() > 0 {
 		reg = &regInfo{}
 	}
 	return &AuxCall{Fn: sym, abiInfo: paramResultInfo, reg: reg}
 }

 // InterfaceAuxCall returns an AuxCall for an interface call.
 func InterfaceAuxCall(paramResultInfo *abi.ABIParamResultInfo) *AuxCall {
 	var reg *regInfo
 	if paramResultInfo.InRegistersUsed()+paramResultInfo.OutRegistersUsed() > 0 {
 		reg = &regInfo{}
 	}
 	return &AuxCall{Fn: nil, abiInfo: paramResultInfo, reg: reg}
 }

 // ClosureAuxCall returns an AuxCall for a closure call.
 func ClosureAuxCall(paramResultInfo *abi.ABIParamResultInfo) *AuxCall {
 	var reg *regInfo
 	if paramResultInfo.InRegistersUsed()+paramResultInfo.OutRegistersUsed() > 0 {
 		reg = &regInfo{}
 	}
 	return &AuxCall{Fn: nil, abiInfo: paramResultInfo, reg: reg}
 }

 func (*AuxCall) CanBeAnSSAAux() {}

 // OwnAuxCall returns a function's own AuxCall.
 func OwnAuxCall(fn *obj.LSym, paramResultInfo *abi.ABIParamResultInfo) *AuxCall {
 	// TODO if this remains identical to ClosureAuxCall above after new ABI is done, should deduplicate.
 	var reg *regInfo
 	if paramResultInfo.InRegistersUsed()+paramResultInfo.OutRegistersUsed() > 0 {
 		reg = &regInfo{}
 	}
 	return &AuxCall{Fn: fn, abiInfo: paramResultInfo, reg: reg}
 }

 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.
 	auxUInt8                  // auxInt is an 8-bit unsigned integer
 	auxFloat32                // auxInt is a float32 (encoded with math.Float64bits)
 	auxFloat64                // auxInt is a float64 (encoded with math.Float64bits)
 	auxFlagConstant           // auxInt is a flagConstant
 	auxNameOffsetInt8         // aux is a &struct{Name ir.Name, Offset int64}; auxInt is index in parameter registers array
 	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)
 	auxCall                   // aux is a *ssa.AuxCall
 	auxCallOff                // aux is a *ssa.AuxCall, AuxInt is int64 param (in+out) size

 	// 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
 	SymWrite
 	SymAddr

 	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 {
 	CanBeAnSSASym()
 	CanBeAnSSAAux()
 }

 // 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() int32   { return int32(int64(x) >> 32) }
 func (x ValAndOff) Val64() int64 { return 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) Off64() int64 { return int64(int32(x)) }
 func (x ValAndOff) Off() int32   { return int32(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))
 }

 func makeValAndOff(val, off int32) ValAndOff {
 	return ValAndOff(int64(val)<<32 + int64(uint32(off)))
 }

 func (x ValAndOff) canAdd32(off int32) bool {
 	newoff := x.Off64() + int64(off)
 	return newoff == int64(int32(newoff))
 }
 func (x ValAndOff) canAdd64(off int64) bool {
 	newoff := x.Off64() + off
 	return newoff == int64(int32(newoff))
 }

 func (x ValAndOff) addOffset32(off int32) ValAndOff {
 	if !x.canAdd32(off) {
 		panic("invalid ValAndOff.addOffset32")
 	}
 	return makeValAndOff(x.Val(), x.Off()+off)
 }
 func (x ValAndOff) addOffset64(off int64) ValAndOff {
 	if !x.canAdd64(off) {
 		panic("invalid ValAndOff.addOffset64")
 	}
 	return makeValAndOff(x.Val(), x.Off()+int32(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
 	BoundsConvert                       // conversion to array pointer failed
 	BoundsKindCount
 )

 // boundsABI 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,
 		BoundsSlice3AlenU,
 		BoundsSlice3Acap,
 		BoundsSlice3AcapU,
 		BoundsConvert:
 		return 0
 	case BoundsSliceAlen,
 		BoundsSliceAlenU,
 		BoundsSliceAcap,
 		BoundsSliceAcapU,
 		BoundsSlice3B,
 		BoundsSlice3BU:
 		return 1
 	case BoundsIndex,
 		BoundsIndexU,
 		BoundsSliceB,
 		BoundsSliceBU,
 		BoundsSlice3C,
 		BoundsSlice3CU:
 		return 2
 	default:
 		panic("bad BoundsKind")
 	}
 }

 // arm64BitField 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
	// 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 (
	"cmd/compile/internal/abi"
	"cmd/compile/internal/ir"
	"cmd/compile/internal/types"
	"cmd/internal/obj"
	"fmt"
	"strings"
	)

	// 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
	needIntTemp bool // need a temporary free integer register
	call bool // is a function call
	tailCall bool // is a tail 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
	}

	func (r *regInfo) String() string {
	s := ""
	s += "INS:\n"
	for _, i := range r.inputs {
	mask := fmt.Sprintf("%64b", i.regs)
	mask = strings.Replace(mask, "0", ".", -1)
	s += fmt.Sprintf("%2d \|%s\|\n", i.idx, mask)
	}
	s += "OUTS:\n"
	for _, i := range r.outputs {
	mask := fmt.Sprintf("%64b", i.regs)
	mask = strings.Replace(mask, "0", ".", -1)
	s += fmt.Sprintf("%2d \|%s\|\n", i.idx, mask)
	}
	s += "CLOBBERS:\n"
	mask := fmt.Sprintf("%64b", r.clobbers)
	mask = strings.Replace(mask, "0", ".", -1)
	s += fmt.Sprintf(" \|%s\|\n", mask)
	return s
	}

	type auxType int8

	type AuxNameOffset struct {
	Name *ir.Name
	Offset int64
	}

	func (a *AuxNameOffset) CanBeAnSSAAux() {}
	func (a *AuxNameOffset) String() string {
	return fmt.Sprintf("%s+%d", a.Name.Sym().Name, a.Offset)
	}

	func (a *AuxNameOffset) FrameOffset() int64 {
	return a.Name.FrameOffset() + a.Offset
	}

	type AuxCall struct {
	Fn *obj.LSym
	reg *regInfo // regInfo for this call
	abiInfo *abi.ABIParamResultInfo
	}

	// Reg returns the regInfo for a given call, combining the derived in/out register masks
	// with the machine-specific register information in the input i. (The machine-specific
	// regInfo is much handier at the call site than it is when the AuxCall is being constructed,
	// therefore do this lazily).
	//
	// TODO: there is a Clever Hack that allows pre-generation of a small-ish number of the slices
	// of inputInfo and outputInfo used here, provided that we are willing to reorder the inputs
	// and outputs from calls, so that all integer registers come first, then all floating registers.
	// At this point (active development of register ABI) that is very premature,
	// but if this turns out to be a cost, we could do it.
	func (a AuxCall) Reg(i regInfo, c Config) regInfo {
	if a.reg.clobbers != 0 {
	// Already updated
	return a.reg
	}
	if a.abiInfo.InRegistersUsed()+a.abiInfo.OutRegistersUsed() == 0 {
	// Shortcut for zero case, also handles old ABI.
	a.reg = i
	return a.reg
	}

	k := len(i.inputs)
	for _, p := range a.abiInfo.InParams() {
	for _, r := range p.Registers {
	m := archRegForAbiReg(r, c)
	a.reg.inputs = append(a.reg.inputs, inputInfo{idx: k, regs: (1 << m)})
	k++
	}
	}
	a.reg.inputs = append(a.reg.inputs, i.inputs...) // These are less constrained, thus should come last
	k = len(i.outputs)
	for _, p := range a.abiInfo.OutParams() {
	for _, r := range p.Registers {
	m := archRegForAbiReg(r, c)
	a.reg.outputs = append(a.reg.outputs, outputInfo{idx: k, regs: (1 << m)})
	k++
	}
	}
	a.reg.outputs = append(a.reg.outputs, i.outputs...)
	a.reg.clobbers = i.clobbers
	return a.reg
	}
	func (a AuxCall) ABI() abi.ABIConfig {
	return a.abiInfo.Config()
	}
	func (a AuxCall) ABIInfo() abi.ABIParamResultInfo {
	return a.abiInfo
	}
	func (a AuxCall) ResultReg(c Config) *regInfo {
	if a.abiInfo.OutRegistersUsed() == 0 {
	return a.reg
	}
	if len(a.reg.inputs) > 0 {
	return a.reg
	}
	k := 0
	for _, p := range a.abiInfo.OutParams() {
	for _, r := range p.Registers {
	m := archRegForAbiReg(r, c)
	a.reg.inputs = append(a.reg.inputs, inputInfo{idx: k, regs: (1 << m)})
	k++
	}
	}
	return a.reg
	}

	// For ABI register index r, returns the (dense) register number used in
	// SSA backend.
	func archRegForAbiReg(r abi.RegIndex, c *Config) uint8 {
	var m int8
	if int(r) < len(c.intParamRegs) {
	m = c.intParamRegs[r]
	} else {
	m = c.floatParamRegs[int(r)-len(c.intParamRegs)]
	}
	return uint8(m)
	}

	// For ABI register index r, returns the register number used in the obj
	// package (assembler).
	func ObjRegForAbiReg(r abi.RegIndex, c *Config) int16 {
	m := archRegForAbiReg(r, c)
	return c.registers[m].objNum
	}

	// ArgWidth returns the amount of stack needed for all the inputs
	// and outputs of a function or method, including ABI-defined parameter
	// slots and ABI-defined spill slots for register-resident parameters.
	//
	// The name is taken from the types package's ArgWidth(<function type>),
	// which predated changes to the ABI; this version handles those changes.
	func (a *AuxCall) ArgWidth() int64 {
	return a.abiInfo.ArgWidth()
	}

	// ParamAssignmentForResult returns the ABI Parameter assignment for result which (indexed 0, 1, etc).
	func (a AuxCall) ParamAssignmentForResult(which int64) abi.ABIParamAssignment {
	return a.abiInfo.OutParam(int(which))
	}

	// OffsetOfResult returns the SP offset of result which (indexed 0, 1, etc).
	func (a *AuxCall) OffsetOfResult(which int64) int64 {
	n := int64(a.abiInfo.OutParam(int(which)).Offset())
	return n
	}

	// OffsetOfArg returns the SP offset of argument which (indexed 0, 1, etc).
	// If the call is to a method, the receiver is the first argument (i.e., index 0)
	func (a *AuxCall) OffsetOfArg(which int64) int64 {
	n := int64(a.abiInfo.InParam(int(which)).Offset())
	return n
	}

	// RegsOfResult returns the register(s) used for result which (indexed 0, 1, etc).
	func (a *AuxCall) RegsOfResult(which int64) []abi.RegIndex {
	return a.abiInfo.OutParam(int(which)).Registers
	}

	// RegsOfArg returns the register(s) used for argument which (indexed 0, 1, etc).
	// If the call is to a method, the receiver is the first argument (i.e., index 0)
	func (a *AuxCall) RegsOfArg(which int64) []abi.RegIndex {
	return a.abiInfo.InParam(int(which)).Registers
	}

	// NameOfResult returns the type of result which (indexed 0, 1, etc).
	func (a AuxCall) NameOfResult(which int64) ir.Name {
	name := a.abiInfo.OutParam(int(which)).Name
	if name == nil {
	return nil
	}
	return name.(*ir.Name)
	}

	// TypeOfResult returns the type of result which (indexed 0, 1, etc).
	func (a AuxCall) TypeOfResult(which int64) types.Type {
	return a.abiInfo.OutParam(int(which)).Type
	}

	// TypeOfArg returns the type of argument which (indexed 0, 1, etc).
	// If the call is to a method, the receiver is the first argument (i.e., index 0)
	func (a AuxCall) TypeOfArg(which int64) types.Type {
	return a.abiInfo.InParam(int(which)).Type
	}

	// SizeOfResult returns the size of result which (indexed 0, 1, etc).
	func (a *AuxCall) SizeOfResult(which int64) int64 {
	return a.TypeOfResult(which).Size()
	}

	// SizeOfArg returns the size of argument which (indexed 0, 1, etc).
	// If the call is to a method, the receiver is the first argument (i.e., index 0)
	func (a *AuxCall) SizeOfArg(which int64) int64 {
	return a.TypeOfArg(which).Size()
	}

	// NResults returns the number of results.
	func (a *AuxCall) NResults() int64 {
	return int64(len(a.abiInfo.OutParams()))
	}

	// LateExpansionResultType returns the result type (including trailing mem)
	// for a call that will be expanded later in the SSA phase.
	func (a AuxCall) LateExpansionResultType() types.Type {
	var tys []*types.Type
	for i := int64(0); i < a.NResults(); i++ {
	tys = append(tys, a.TypeOfResult(i))
	}
	tys = append(tys, types.TypeMem)
	return types.NewResults(tys)
	}

	// NArgs returns the number of arguments (including receiver, if there is one).
	func (a *AuxCall) NArgs() int64 {
	return int64(len(a.abiInfo.InParams()))
	}

	// String returns "AuxCall{<fn>}"
	func (a *AuxCall) String() string {
	var fn string
	if a.Fn == nil {
	fn = "AuxCall{nil" // could be interface/closure etc.
	} else {
	fn = fmt.Sprintf("AuxCall{%v", a.Fn)
	}
	// TODO how much of the ABI should be printed?

	return fn + "}"
	}

	// StaticAuxCall returns an AuxCall for a static call.
	func StaticAuxCall(sym obj.LSym, paramResultInfo abi.ABIParamResultInfo) *AuxCall {
	if paramResultInfo == nil {
	panic(fmt.Errorf("Nil paramResultInfo, sym=%v", sym))
	}
	var reg *regInfo
	if paramResultInfo.InRegistersUsed()+paramResultInfo.OutRegistersUsed() > 0 {
	reg = &regInfo{}
	}
	return &AuxCall{Fn: sym, abiInfo: paramResultInfo, reg: reg}
	}

	// InterfaceAuxCall returns an AuxCall for an interface call.
	func InterfaceAuxCall(paramResultInfo abi.ABIParamResultInfo) AuxCall {
	var reg *regInfo
	if paramResultInfo.InRegistersUsed()+paramResultInfo.OutRegistersUsed() > 0 {
	reg = &regInfo{}
	}
	return &AuxCall{Fn: nil, abiInfo: paramResultInfo, reg: reg}
	}

	// ClosureAuxCall returns an AuxCall for a closure call.
	func ClosureAuxCall(paramResultInfo abi.ABIParamResultInfo) AuxCall {
	var reg *regInfo
	if paramResultInfo.InRegistersUsed()+paramResultInfo.OutRegistersUsed() > 0 {
	reg = &regInfo{}
	}
	return &AuxCall{Fn: nil, abiInfo: paramResultInfo, reg: reg}
	}

	func (*AuxCall) CanBeAnSSAAux() {}

	// OwnAuxCall returns a function's own AuxCall.
	func OwnAuxCall(fn obj.LSym, paramResultInfo abi.ABIParamResultInfo) *AuxCall {
	// TODO if this remains identical to ClosureAuxCall above after new ABI is done, should deduplicate.
	var reg *regInfo
	if paramResultInfo.InRegistersUsed()+paramResultInfo.OutRegistersUsed() > 0 {
	reg = &regInfo{}
	}
	return &AuxCall{Fn: fn, abiInfo: paramResultInfo, reg: reg}
	}

	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.
	auxUInt8 // auxInt is an 8-bit unsigned integer
	auxFloat32 // auxInt is a float32 (encoded with math.Float64bits)
	auxFloat64 // auxInt is a float64 (encoded with math.Float64bits)
	auxFlagConstant // auxInt is a flagConstant
	auxNameOffsetInt8 // aux is a &struct{Name ir.Name, Offset int64}; auxInt is index in parameter registers array
	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)
	auxCall // aux is a *ssa.AuxCall
	auxCallOff // aux is a *ssa.AuxCall, AuxInt is int64 param (in+out) size

	// 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
	SymWrite
	SymAddr

	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 {
	CanBeAnSSASym()
	CanBeAnSSAAux()
	}

	// 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() int32 { return int32(int64(x) >> 32) }
	func (x ValAndOff) Val64() int64 { return 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) Off64() int64 { return int64(int32(x)) }
	func (x ValAndOff) Off() int32 { return int32(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))
	}

	func makeValAndOff(val, off int32) ValAndOff {
	return ValAndOff(int64(val)<<32 + int64(uint32(off)))
	}

	func (x ValAndOff) canAdd32(off int32) bool {
	newoff := x.Off64() + int64(off)
	return newoff == int64(int32(newoff))
	}
	func (x ValAndOff) canAdd64(off int64) bool {
	newoff := x.Off64() + off
	return newoff == int64(int32(newoff))
	}

	func (x ValAndOff) addOffset32(off int32) ValAndOff {
	if !x.canAdd32(off) {
	panic("invalid ValAndOff.addOffset32")
	}
	return makeValAndOff(x.Val(), x.Off()+off)
	}
	func (x ValAndOff) addOffset64(off int64) ValAndOff {
	if !x.canAdd64(off) {
	panic("invalid ValAndOff.addOffset64")
	}
	return makeValAndOff(x.Val(), x.Off()+int32(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
	BoundsConvert // conversion to array pointer failed
	BoundsKindCount
	)

	// boundsABI 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,
	BoundsSlice3AlenU,
	BoundsSlice3Acap,
	BoundsSlice3AcapU,
	BoundsConvert:
	return 0
	case BoundsSliceAlen,
	BoundsSliceAlenU,
	BoundsSliceAcap,
	BoundsSliceAcapU,
	BoundsSlice3B,
	BoundsSlice3BU:
	return 1
	case BoundsIndex,
	BoundsIndexU,
	BoundsSliceB,
	BoundsSliceBU,
	BoundsSlice3C,
	BoundsSlice3CU:
	return 2
	default:
	panic("bad BoundsKind")
	}
	}

	// arm64BitField 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