// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ssa
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import (
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"cmd/compile/internal/types"
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"fmt"
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)
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// A place that an ssa variable can reside.
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type Location interface {
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String() string // name to use in assembly templates: AX, 16(SP), ...
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}
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// A Register is a machine register, like AX.
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// They are numbered densely from 0 (for each architecture).
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type Register struct {
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num int32 // dense numbering
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objNum int16 // register number from cmd/internal/obj/$ARCH
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gcNum int16 // GC register map number (dense numbering of registers that can contain pointers)
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name string
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}
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func (r *Register) String() string {
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return r.name
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}
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// ObjNum returns the register number from cmd/internal/obj/$ARCH that
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// corresponds to this register.
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func (r *Register) ObjNum() int16 {
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return r.objNum
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}
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// GCNum returns the runtime GC register index of r, or -1 if this
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// register can't contain pointers.
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func (r *Register) GCNum() int16 {
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return r.gcNum
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}
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// A LocalSlot is a location in the stack frame, which identifies and stores
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// part or all of a PPARAM, PPARAMOUT, or PAUTO ONAME node.
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// It can represent a whole variable, part of a larger stack slot, or part of a
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// variable that has been decomposed into multiple stack slots.
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// As an example, a string could have the following configurations:
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//
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// stack layout LocalSlots
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//
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// Optimizations are disabled. s is on the stack and represented in its entirety.
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// [ ------- s string ---- ] { N: s, Type: string, Off: 0 }
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//
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// s was not decomposed, but the SSA operates on its parts individually, so
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// there is a LocalSlot for each of its fields that points into the single stack slot.
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// [ ------- s string ---- ] { N: s, Type: *uint8, Off: 0 }, {N: s, Type: int, Off: 8}
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//
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// s was decomposed. Each of its fields is in its own stack slot and has its own LocalSLot.
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// [ ptr *uint8 ] [ len int] { N: ptr, Type: *uint8, Off: 0, SplitOf: parent, SplitOffset: 0},
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// { N: len, Type: int, Off: 0, SplitOf: parent, SplitOffset: 8}
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// parent = &{N: s, Type: string}
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type LocalSlot struct {
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N GCNode // an ONAME *gc.Node representing a stack location.
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Type *types.Type // type of slot
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Off int64 // offset of slot in N
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SplitOf *LocalSlot // slot is a decomposition of SplitOf
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SplitOffset int64 // .. at this offset.
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}
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func (s LocalSlot) String() string {
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if s.Off == 0 {
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return fmt.Sprintf("%v[%v]", s.N, s.Type)
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}
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return fmt.Sprintf("%v+%d[%v]", s.N, s.Off, s.Type)
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}
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type LocPair [2]Location
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func (t LocPair) String() string {
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n0, n1 := "nil", "nil"
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if t[0] != nil {
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n0 = t[0].String()
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}
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if t[1] != nil {
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n1 = t[1].String()
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}
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return fmt.Sprintf("<%s,%s>", n0, n1)
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}
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