scope.go

     1  // Copyright 2017 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 dwarfgen
     6  
     7  import (
     8  	"sort"
     9  
    10  	"cmd/compile/internal/base"
    11  	"cmd/compile/internal/ir"
    12  	"cmd/internal/dwarf"
    13  	"cmd/internal/obj"
    14  	"cmd/internal/src"
    15  )
    16  
    17  // See golang.org/issue/20390.
    18  func xposBefore(p, q src.XPos) bool {
    19  	return base.Ctxt.PosTable.Pos(p).Before(base.Ctxt.PosTable.Pos(q))
    20  }
    21  
    22  func findScope(marks []ir.Mark, pos src.XPos) ir.ScopeID {
    23  	i := sort.Search(len(marks), func(i int) bool {
    24  		return xposBefore(pos, marks[i].Pos)
    25  	})
    26  	if i == 0 {
    27  		return 0
    28  	}
    29  	return marks[i-1].Scope
    30  }
    31  
    32  func assembleScopes(fnsym *obj.LSym, fn *ir.Func, dwarfVars []*dwarf.Var, varScopes []ir.ScopeID) []dwarf.Scope {
    33  	// Initialize the DWARF scope tree based on lexical scopes.
    34  	dwarfScopes := make([]dwarf.Scope, 1+len(fn.Parents))
    35  	for i, parent := range fn.Parents {
    36  		dwarfScopes[i+1].Parent = int32(parent)
    37  	}
    38  
    39  	scopeVariables(dwarfVars, varScopes, dwarfScopes, fnsym.ABI() != obj.ABI0)
    40  	if fnsym.Func().Text != nil {
    41  		scopePCs(fnsym, fn.Marks, dwarfScopes)
    42  	}
    43  	return compactScopes(dwarfScopes)
    44  }
    45  
    46  // scopeVariables assigns DWARF variable records to their scopes.
    47  func scopeVariables(dwarfVars []*dwarf.Var, varScopes []ir.ScopeID, dwarfScopes []dwarf.Scope, regabi bool) {
    48  	if regabi {
    49  		sort.Stable(varsByScope{dwarfVars, varScopes})
    50  	} else {
    51  		sort.Stable(varsByScopeAndOffset{dwarfVars, varScopes})
    52  	}
    53  
    54  	i0 := 0
    55  	for i := range dwarfVars {
    56  		if varScopes[i] == varScopes[i0] {
    57  			continue
    58  		}
    59  		dwarfScopes[varScopes[i0]].Vars = dwarfVars[i0:i]
    60  		i0 = i
    61  	}
    62  	if i0 < len(dwarfVars) {
    63  		dwarfScopes[varScopes[i0]].Vars = dwarfVars[i0:]
    64  	}
    65  }
    66  
    67  // scopePCs assigns PC ranges to their scopes.
    68  func scopePCs(fnsym *obj.LSym, marks []ir.Mark, dwarfScopes []dwarf.Scope) {
    69  	// If there aren't any child scopes (in particular, when scope
    70  	// tracking is disabled), we can skip a whole lot of work.
    71  	if len(marks) == 0 {
    72  		return
    73  	}
    74  	p0 := fnsym.Func().Text
    75  	scope := findScope(marks, p0.Pos)
    76  	for p := p0; p != nil; p = p.Link {
    77  		if p.Pos == p0.Pos {
    78  			continue
    79  		}
    80  		dwarfScopes[scope].AppendRange(dwarf.Range{Start: p0.Pc, End: p.Pc})
    81  		p0 = p
    82  		scope = findScope(marks, p0.Pos)
    83  	}
    84  	if p0.Pc < fnsym.Size {
    85  		dwarfScopes[scope].AppendRange(dwarf.Range{Start: p0.Pc, End: fnsym.Size})
    86  	}
    87  }
    88  
    89  func compactScopes(dwarfScopes []dwarf.Scope) []dwarf.Scope {
    90  	// Reverse pass to propagate PC ranges to parent scopes.
    91  	for i := len(dwarfScopes) - 1; i > 0; i-- {
    92  		s := &dwarfScopes[i]
    93  		dwarfScopes[s.Parent].UnifyRanges(s)
    94  	}
    95  
    96  	return dwarfScopes
    97  }
    98  
    99  type varsByScopeAndOffset struct {
   100  	vars   []*dwarf.Var
   101  	scopes []ir.ScopeID
   102  }
   103  
   104  func (v varsByScopeAndOffset) Len() int {
   105  	return len(v.vars)
   106  }
   107  
   108  func (v varsByScopeAndOffset) Less(i, j int) bool {
   109  	if v.scopes[i] != v.scopes[j] {
   110  		return v.scopes[i] < v.scopes[j]
   111  	}
   112  	return v.vars[i].StackOffset < v.vars[j].StackOffset
   113  }
   114  
   115  func (v varsByScopeAndOffset) Swap(i, j int) {
   116  	v.vars[i], v.vars[j] = v.vars[j], v.vars[i]
   117  	v.scopes[i], v.scopes[j] = v.scopes[j], v.scopes[i]
   118  }
   119  
   120  type varsByScope struct {
   121  	vars   []*dwarf.Var
   122  	scopes []ir.ScopeID
   123  }
   124  
   125  func (v varsByScope) Len() int {
   126  	return len(v.vars)
   127  }
   128  
   129  func (v varsByScope) Less(i, j int) bool {
   130  	return v.scopes[i] < v.scopes[j]
   131  }
   132  
   133  func (v varsByScope) Swap(i, j int) {
   134  	v.vars[i], v.vars[j] = v.vars[j], v.vars[i]
   135  	v.scopes[i], v.scopes[j] = v.scopes[j], v.scopes[i]
   136  }
   137
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