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/internal/obj" 9 "fmt" 10 ) 11 12 // An Op encodes the specific operation that a Value performs. 13 // Opcodes' semantics can be modified by the type and aux fields of the Value. 14 // For instance, OpAdd can be 32 or 64 bit, signed or unsigned, float or complex, depending on Value.Type. 15 // Semantics of each op are described in the opcode files in gen/*Ops.go. 16 // There is one file for generic (architecture-independent) ops and one file 17 // for each architecture. 18 type Op int32 19 20 type opInfo struct { 21 name string 22 reg regInfo 23 auxType auxType 24 argLen int32 // the number of arguments, -1 if variable length 25 asm obj.As 26 generic bool // this is a generic (arch-independent) opcode 27 rematerializeable bool // this op is rematerializeable 28 commutative bool // this operation is commutative (e.g. addition) 29 resultInArg0 bool // (first, if a tuple) output of v and v.Args[0] must be allocated to the same register 30 resultNotInArgs bool // outputs must not be allocated to the same registers as inputs 31 clobberFlags bool // this op clobbers flags register 32 call bool // is a function call 33 nilCheck bool // this op is a nil check on arg0 34 faultOnNilArg0 bool // this op will fault if arg0 is nil (and aux encodes a small offset) 35 faultOnNilArg1 bool // this op will fault if arg1 is nil (and aux encodes a small offset) 36 usesScratch bool // this op requires scratch memory space 37 hasSideEffects bool // for "reasons", not to be eliminated. E.g., atomic store, #19182. 38 symEffect SymEffect // effect this op has on symbol in aux 39 } 40 41 type inputInfo struct { 42 idx int // index in Args array 43 regs regMask // allowed input registers 44 } 45 46 type outputInfo struct { 47 idx int // index in output tuple 48 regs regMask // allowed output registers 49 } 50 51 type regInfo struct { 52 inputs []inputInfo // ordered in register allocation order 53 clobbers regMask 54 outputs []outputInfo // ordered in register allocation order 55 } 56 57 type auxType int8 58 59 const ( 60 auxNone auxType = iota 61 auxBool // auxInt is 0/1 for false/true 62 auxInt8 // auxInt is an 8-bit integer 63 auxInt16 // auxInt is a 16-bit integer 64 auxInt32 // auxInt is a 32-bit integer 65 auxInt64 // auxInt is a 64-bit integer 66 auxInt128 // auxInt represents a 128-bit integer. Always 0. 67 auxFloat32 // auxInt is a float32 (encoded with math.Float64bits) 68 auxFloat64 // auxInt is a float64 (encoded with math.Float64bits) 69 auxString // aux is a string 70 auxSym // aux is a symbol (a *gc.Node for locals or an *obj.LSym for globals) 71 auxSymOff // aux is a symbol, auxInt is an offset 72 auxSymValAndOff // aux is a symbol, auxInt is a ValAndOff 73 auxTyp // aux is a type 74 auxTypSize // aux is a type, auxInt is a size, must have Aux.(Type).Size() == AuxInt 75 76 auxSymInt32 // aux is a symbol, auxInt is a 32-bit integer 77 ) 78 79 // A SymEffect describes the effect that an SSA Value has on the variable 80 // identified by the symbol in its Aux field. 81 type SymEffect int8 82 83 const ( 84 SymRead SymEffect = 1 << iota 85 SymWrite 86 SymAddr 87 88 SymRdWr = SymRead | SymWrite 89 90 SymNone SymEffect = 0 91 ) 92 93 // A ValAndOff is used by the several opcodes. It holds 94 // both a value and a pointer offset. 95 // A ValAndOff is intended to be encoded into an AuxInt field. 96 // The zero ValAndOff encodes a value of 0 and an offset of 0. 97 // The high 32 bits hold a value. 98 // The low 32 bits hold a pointer offset. 99 type ValAndOff int64 100 101 func (x ValAndOff) Val() int64 { 102 return int64(x) >> 32 103 } 104 func (x ValAndOff) Off() int64 { 105 return int64(int32(x)) 106 } 107 func (x ValAndOff) Int64() int64 { 108 return int64(x) 109 } 110 func (x ValAndOff) String() string { 111 return fmt.Sprintf("val=%d,off=%d", x.Val(), x.Off()) 112 } 113 114 // validVal reports whether the value can be used 115 // as an argument to makeValAndOff. 116 func validVal(val int64) bool { 117 return val == int64(int32(val)) 118 } 119 120 // validOff reports whether the offset can be used 121 // as an argument to makeValAndOff. 122 func validOff(off int64) bool { 123 return off == int64(int32(off)) 124 } 125 126 // validValAndOff reports whether we can fit the value and offset into 127 // a ValAndOff value. 128 func validValAndOff(val, off int64) bool { 129 if !validVal(val) { 130 return false 131 } 132 if !validOff(off) { 133 return false 134 } 135 return true 136 } 137 138 // makeValAndOff encodes a ValAndOff into an int64 suitable for storing in an AuxInt field. 139 func makeValAndOff(val, off int64) int64 { 140 if !validValAndOff(val, off) { 141 panic("invalid makeValAndOff") 142 } 143 return ValAndOff(val<<32 + int64(uint32(off))).Int64() 144 } 145 146 func (x ValAndOff) canAdd(off int64) bool { 147 newoff := x.Off() + off 148 return newoff == int64(int32(newoff)) 149 } 150 151 func (x ValAndOff) add(off int64) int64 { 152 if !x.canAdd(off) { 153 panic("invalid ValAndOff.add") 154 } 155 return makeValAndOff(x.Val(), x.Off()+off) 156 } 157
