1 // Copyright 2015 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package ssa 6 7 import ( 8 "cmd/compile/internal/types" 9 "fmt" 10 ) 11 12 // A place that an ssa variable can reside. 13 type Location interface { 14 String() string // name to use in assembly templates: AX, 16(SP), ... 15 } 16 17 // A Register is a machine register, like AX. 18 // They are numbered densely from 0 (for each architecture). 19 type Register struct { 20 num int32 // dense numbering 21 objNum int16 // register number from cmd/internal/obj/$ARCH 22 gcNum int16 // GC register map number (dense numbering of registers that can contain pointers) 23 name string 24 } 25 26 func (r *Register) String() string { 27 return r.name 28 } 29 30 // ObjNum returns the register number from cmd/internal/obj/$ARCH that 31 // corresponds to this register. 32 func (r *Register) ObjNum() int16 { 33 return r.objNum 34 } 35 36 // GCNum returns the runtime GC register index of r, or -1 if this 37 // register can't contain pointers. 38 func (r *Register) GCNum() int16 { 39 return r.gcNum 40 } 41 42 // A LocalSlot is a location in the stack frame, which identifies and stores 43 // part or all of a PPARAM, PPARAMOUT, or PAUTO ONAME node. 44 // It can represent a whole variable, part of a larger stack slot, or part of a 45 // variable that has been decomposed into multiple stack slots. 46 // As an example, a string could have the following configurations: 47 // 48 // stack layout LocalSlots 49 // 50 // Optimizations are disabled. s is on the stack and represented in its entirety. 51 // [ ------- s string ---- ] { N: s, Type: string, Off: 0 } 52 // 53 // s was not decomposed, but the SSA operates on its parts individually, so 54 // there is a LocalSlot for each of its fields that points into the single stack slot. 55 // [ ------- s string ---- ] { N: s, Type: *uint8, Off: 0 }, {N: s, Type: int, Off: 8} 56 // 57 // s was decomposed. Each of its fields is in its own stack slot and has its own LocalSLot. 58 // [ ptr *uint8 ] [ len int] { N: ptr, Type: *uint8, Off: 0, SplitOf: parent, SplitOffset: 0}, 59 // { N: len, Type: int, Off: 0, SplitOf: parent, SplitOffset: 8} 60 // parent = &{N: s, Type: string} 61 type LocalSlot struct { 62 N GCNode // an ONAME *gc.Node representing a stack location. 63 Type *types.Type // type of slot 64 Off int64 // offset of slot in N 65 66 SplitOf *LocalSlot // slot is a decomposition of SplitOf 67 SplitOffset int64 // .. at this offset. 68 } 69 70 func (s LocalSlot) String() string { 71 if s.Off == 0 { 72 return fmt.Sprintf("%v[%v]", s.N, s.Type) 73 } 74 return fmt.Sprintf("%v+%d[%v]", s.N, s.Off, s.Type) 75 } 76 77 type LocPair [2]Location 78 79 func (t LocPair) String() string { 80 n0, n1 := "nil", "nil" 81 if t[0] != nil { 82 n0 = t[0].String() 83 } 84 if t[1] != nil { 85 n1 = t[1].String() 86 } 87 return fmt.Sprintf("<%s,%s>", n0, n1) 88 } 89