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cmd/compile: include non-decomposed vars for -dwarflocationlists

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When enhanced DWARF location list generation is enabled (via internal
option -dwarflocationlists), variable entries were missing for "large"
(non-decomposable) locals and formals. From the debugging perspective,
this makes it appear that the variable doesn't exist, which is
probably not what we want. This change insures that a formal/local DIE
is created for these vars (with correct type, line, etc) but with a
conservative ("no info") location.

Change-Id: I10b2e9a51a60c7b4c748e987cdec5f2d8b2837d5
Reviewed-on: https://go-review.googlesource.com/72630
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
This commit is contained in:
Than McIntosh 2017-10-23 11:41:47 -04:00
parent 0316d6618c
commit 87f83eac7f
1 changed files with 37 additions and 2 deletions
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39
src/cmd/compile/internal/gc/pgen.go
View File

@ -338,7 +338,7 @@ func debuginfo(fnsym *obj.LSym, curfn interface{}) []dwarf.Scope {
var dwarfVars []*dwarf.Var
var decls []*Node
if Ctxt.Flag_locationlists && Ctxt.Flag_optimize {
decls, dwarfVars = createComplexVars(fnsym, debugInfo)
decls, dwarfVars = createComplexVars(fnsym, debugInfo, automDecls)
} else {
decls, dwarfVars = createSimpleVars(automDecls)
}
@ -416,7 +416,7 @@ type varPart struct {
slot ssa.SlotID
}
func createComplexVars(fnsym *obj.LSym, debugInfo *ssa.FuncDebug) ([]*Node, []*dwarf.Var) {
func createComplexVars(fnsym *obj.LSym, debugInfo *ssa.FuncDebug, automDecls []*Node) ([]*Node, []*dwarf.Var) {
for _, blockDebug := range debugInfo.Blocks {
for _, locList := range blockDebug.Variables {
for _, loc := range locList.Locations {
@ -438,11 +438,13 @@ func createComplexVars(fnsym *obj.LSym, debugInfo *ssa.FuncDebug) ([]*Node, []*d
// Group SSA variables by the user variable they were decomposed from.
varParts := map[*Node][]varPart{}
ssaVars := make(map[*Node]bool)
for slotID, slot := range debugInfo.VarSlots {
for slot.SplitOf != nil {
slot = slot.SplitOf
}
n := slot.N.(*Node)
ssaVars[n] = true
varParts[n] = append(varParts[n], varPart{varOffset(slot), ssa.SlotID(slotID)})
}
@ -472,6 +474,39 @@ func createComplexVars(fnsym *obj.LSym, debugInfo *ssa.FuncDebug) ([]*Node, []*d
vars = append(vars, dvar)
}
}
// The machinery above will create a dwarf.Var for only those
// variables that are decomposed into SSA names. Fill in the list
// with entries for the remaining variables (including things too
// big to decompose). Since optimization is enabled, the recipe
// below creates a conservative location. The idea here is that we
// want to communicate to the user that "yes, there is a variable
// named X in this function, but no, I don't have enough
// information to reliably report its contents."
for _, n := range automDecls {
if _, found := ssaVars[n]; !found {
continue
}
c := n.Sym.Name[0]
if c == '~' || c == '.' {
continue
}
typename := dwarf.InfoPrefix + typesymname(n.Type)
decls = append(decls, n)
abbrev := dwarf.DW_ABRV_AUTO_LOCLIST
if n.Class() == PPARAM || n.Class() == PPARAMOUT {
abbrev = dwarf.DW_ABRV_PARAM_LOCLIST
}
vars = append(vars, &dwarf.Var{
Name: n.Sym.Name,
IsReturnValue: n.Class() == PPARAMOUT,
Abbrev: abbrev,
StackOffset: int32(n.Xoffset),
Type: Ctxt.Lookup(typename),
DeclLine: n.Pos.Line(),
})
}
return decls, vars
}