...
Run Format

Source file src/cmd/compile/internal/ssa/location.go

Documentation: cmd/compile/internal/ssa

     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  

View as plain text