location.go

     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/ir"
     9  	"cmd/compile/internal/types"
    10  	"fmt"
    11  )
    12  
    13  // A place that an ssa variable can reside.
    14  type Location interface {
    15  	String() string // name to use in assembly templates: AX, 16(SP), ...
    16  }
    17  
    18  // A Register is a machine register, like AX.
    19  // They are numbered densely from 0 (for each architecture).
    20  type Register struct {
    21  	num    int32 // dense numbering
    22  	objNum int16 // register number from cmd/internal/obj/$ARCH
    23  	name   string
    24  }
    25  
    26  func (r *Register) String() string {
    27  	return r.name
    28  }
    29  
    30  // ObjNum returns the register number from cmd/internal/obj/$ARCH that
    31  // corresponds to this register.
    32  func (r *Register) ObjNum() int16 {
    33  	return r.objNum
    34  }
    35  
    36  // A LocalSlot is a location in the stack frame, which identifies and stores
    37  // part or all of a PPARAM, PPARAMOUT, or PAUTO ONAME node.
    38  // It can represent a whole variable, part of a larger stack slot, or part of a
    39  // variable that has been decomposed into multiple stack slots.
    40  // As an example, a string could have the following configurations:
    41  //
    42  //	          stack layout              LocalSlots
    43  //
    44  //	Optimizations are disabled. s is on the stack and represented in its entirety.
    45  //	[ ------- s string ---- ] { N: s, Type: string, Off: 0 }
    46  //
    47  //	s was not decomposed, but the SSA operates on its parts individually, so
    48  //	there is a LocalSlot for each of its fields that points into the single stack slot.
    49  //	[ ------- s string ---- ] { N: s, Type: *uint8, Off: 0 }, {N: s, Type: int, Off: 8}
    50  //
    51  //	s was decomposed. Each of its fields is in its own stack slot and has its own LocalSLot.
    52  //	[ ptr *uint8 ] [ len int] { N: ptr, Type: *uint8, Off: 0, SplitOf: parent, SplitOffset: 0},
    53  //	                          { N: len, Type: int, Off: 0, SplitOf: parent, SplitOffset: 8}
    54  //	                          parent = &{N: s, Type: string}
    55  type LocalSlot struct {
    56  	N    *ir.Name    // an ONAME *ir.Name representing a stack location.
    57  	Type *types.Type // type of slot
    58  	Off  int64       // offset of slot in N
    59  
    60  	SplitOf     *LocalSlot // slot is a decomposition of SplitOf
    61  	SplitOffset int64      // .. at this offset.
    62  }
    63  
    64  func (s LocalSlot) String() string {
    65  	if s.Off == 0 {
    66  		return fmt.Sprintf("%v[%v]", s.N, s.Type)
    67  	}
    68  	return fmt.Sprintf("%v+%d[%v]", s.N, s.Off, s.Type)
    69  }
    70  
    71  type LocPair [2]Location
    72  
    73  func (t LocPair) String() string {
    74  	n0, n1 := "nil", "nil"
    75  	if t[0] != nil {
    76  		n0 = t[0].String()
    77  	}
    78  	if t[1] != nil {
    79  		n1 = t[1].String()
    80  	}
    81  	return fmt.Sprintf("<%s,%s>", n0, n1)
    82  }
    83  
    84  type LocResults []Location
    85  
    86  func (t LocResults) String() string {
    87  	s := ""
    88  	a := "<"
    89  	for _, r := range t {
    90  		a += s
    91  		s = ","
    92  		a += r.String()
    93  	}
    94  	a += ">"
    95  	return a
    96  }
    97  
    98  type Spill struct {
    99  	Type   *types.Type
   100  	Offset int64
   101  	Reg    int16
   102  }
   103
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