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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 (
"cmd/compile/internal/types"
"fmt"
)
// A place that an ssa variable can reside.
type Location interface {
Name() string // name to use in assembly templates: %rax, 16(%rsp), ...
}
// A Register is a machine register, like %rax.
// They are numbered densely from 0 (for each architecture).
type Register struct {
num int32
objNum int16 // register number from cmd/internal/obj/$ARCH
name string
}
func (r *Register) Name() string {
return r.name
}
// A LocalSlot is a location in the stack frame, which identifies and stores
// part or all of a PPARAM, PPARAMOUT, or PAUTO ONAME node.
// It can represent a whole variable, part of a larger stack slot, or part of a
// variable that has been decomposed into multiple stack slots.
// As an example, a string could have the following configurations:
//
// stack layout LocalSlots
//
// Optimizations are disabled. s is on the stack and represented in its entirety.
// [ ------- s string ---- ] { N: s, Type: string, Off: 0 }
//
// s was not decomposed, but the SSA operates on its parts individually, so
// there is a LocalSlot for each of its fields that points into the single stack slot.
// [ ------- s string ---- ] { N: s, Type: *uint8, Off: 0 }, {N: s, Type: int, Off: 8}
//
// s was decomposed. Each of its fields is in its own stack slot and has its own LocalSLot.
// [ ptr *uint8 ] [ len int] { N: ptr, Type: *uint8, Off: 0, SplitOf: parent, SplitOffset: 0},
// { N: len, Type: int, Off: 0, SplitOf: parent, SplitOffset: 8}
// parent = &{N: s, Type: string}
type LocalSlot struct {
N GCNode // an ONAME *gc.Node representing a stack location.
Type *types.Type // type of slot
Off int64 // offset of slot in N
SplitOf *LocalSlot // slot is a decomposition of SplitOf
SplitOffset int64 // .. at this offset.
}
func (s LocalSlot) Name() string {
if s.Off == 0 {
return fmt.Sprintf("%v[%v]", s.N, s.Type)
}
return fmt.Sprintf("%v+%d[%v]", s.N, s.Off, s.Type)
}
type LocPair [2]Location
func (t LocPair) Name() string {
n0, n1 := "nil", "nil"
if t[0] != nil {
n0 = t[0].Name()
}
if t[1] != nil {
n1 = t[1].Name()
}
return fmt.Sprintf("<%s,%s>", n0, n1)
}
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