cmd/compile: drop internal range-over-func vars from DWARF output

Drops internal range-over-func variables from the DWARF output
(excluding #yield which is used by Delve).

Fixes #68238

Change-Id: Ic035e37ca3560347276cdc3b469fd564da33f4f5
Reviewed-on: https://go-review.googlesource.com/c/go/+/594257
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Auto-Submit: Hyang-Ah Hana Kim <hyangah@gmail.com>

diff --git a/src/cmd/compile/internal/dwarfgen/dwarf.go b/src/cmd/compile/internal/dwarfgen/dwarf.go
index 512d8d22e757b6198d496b67df1bbd949be529ed..36cc253e827de5856f72dce4fcacd6b0061e0ca1 100644 (file)
--- a/src/cmd/compile/internal/dwarfgen/dwarf.go
+++ b/src/cmd/compile/internal/dwarfgen/dwarf.go
@@ -91,6 +91,9 @@ func Info(fnsym *obj.LSym, infosym *obj.LSym, curfn obj.Func) (scopes []dwarf.Sc
                        default:
                                continue
                        }
+                       if !ssa.IsVarWantedForDebug(n) {
+                               continue
+                       }
                        apdecls = append(apdecls, n)
                        if n.Type().Kind() == types.TSSA {
                                // Can happen for TypeInt128 types. This only happens for
@@ -194,6 +197,9 @@ func createDwarfVars(fnsym *obj.LSym, complexOK bool, fn *ir.Func, apDecls []*ir
                // DWARF-gen. See issue 48573 for more details.
                debugInfo := fn.DebugInfo.(*ssa.FuncDebug)
                for _, n := range debugInfo.RegOutputParams {
+                       if !ssa.IsVarWantedForDebug(n) {
+                               continue
+                       }
                        if n.Class != ir.PPARAMOUT || !n.IsOutputParamInRegisters() {
                                panic("invalid ir.Name on debugInfo.RegOutputParams list")
                        }

diff --git a/src/cmd/compile/internal/rangefunc/rewrite.go b/src/cmd/compile/internal/rangefunc/rewrite.go
index e5a0b9f8af141780bed94fd39b6c7ec8971c4201..ba2eb8d0fdcf757f7d169437f0d63db64a3bec94 100644 (file)
--- a/src/cmd/compile/internal/rangefunc/rewrite.go
+++ b/src/cmd/compile/internal/rangefunc/rewrite.go
@@ -1137,7 +1137,7 @@ func (r *rewriter) setStateAt(index int, stateVal abi.RF_State) *syntax.AssignSt
 func (r *rewriter) bodyFunc(body []syntax.Stmt, lhs []syntax.Expr, def bool, ftyp *types2.Signature, start, end syntax.Pos) *syntax.FuncLit {
        // Starting X(bodyFunc); build up bodyFunc first.
        var params, results []*types2.Var
-       results = append(results, types2.NewVar(start, nil, "", r.bool.Type()))
+       results = append(results, types2.NewVar(start, nil, "#r", r.bool.Type()))
        bodyFunc := &syntax.FuncLit{
                // Note: Type is ignored but needs to be non-nil to avoid panic in syntax.Inspect.
                Type: &syntax.FuncType{},

diff --git a/src/cmd/compile/internal/ssa/debug.go b/src/cmd/compile/internal/ssa/debug.go
index 4abe5a98924f49e1067a47a12dbc0face3a83e78..04025f78829a50cd01745a41e647da8968844013 100644 (file)
--- a/src/cmd/compile/internal/ssa/debug.go
+++ b/src/cmd/compile/internal/ssa/debug.go
@@ -600,7 +600,7 @@ func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingLevel int, stackOffset func(
        state.vars = state.vars[:0]
        for i, slot := range f.Names {
                state.slots = append(state.slots, *slot)
-               if ir.IsSynthetic(slot.N) {
+               if ir.IsSynthetic(slot.N) || !IsVarWantedForDebug(slot.N) {
                        continue
                }
 
@@ -620,7 +620,7 @@ func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingLevel int, stackOffset func(
                for _, v := range b.Values {
                        if v.Op == OpVarDef {
                                n := v.Aux.(*ir.Name)
-                               if ir.IsSynthetic(n) {
+                               if ir.IsSynthetic(n) || !IsVarWantedForDebug(n) {
                                        continue
                                }
 
@@ -665,7 +665,7 @@ func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingLevel int, stackOffset func(
        state.initializeCache(f, len(state.varParts), len(state.slots))
 
        for i, slot := range f.Names {
-               if ir.IsSynthetic(slot.N) {
+               if ir.IsSynthetic(slot.N) || !IsVarWantedForDebug(slot.N) {
                        continue
                }
                for _, value := range f.NamedValues[*slot] {
@@ -1087,7 +1087,7 @@ func (state *debugState) processValue(v *Value, vSlots []SlotID, vReg *Register)
        switch {
        case v.Op == OpVarDef:
                n := v.Aux.(*ir.Name)
-               if ir.IsSynthetic(n) {
+               if ir.IsSynthetic(n) || !IsVarWantedForDebug(n) {
                        break
                }
 
@@ -1835,6 +1835,9 @@ func BuildFuncDebugNoOptimized(ctxt *obj.Link, f *Func, loggingEnabled bool, sta
                        // will be sorted out elsewhere
                        continue
                }
+               if !IsVarWantedForDebug(inp.Name) {
+                       continue
+               }
                addVarSlot(inp.Name, inp.Type)
                params = append(params, inp)
        }
@@ -1855,6 +1858,9 @@ func BuildFuncDebugNoOptimized(ctxt *obj.Link, f *Func, loggingEnabled bool, sta
                        // will be sorted out elsewhere
                        continue
                }
+               if !IsVarWantedForDebug(inp.Name) {
+                       continue
+               }
 
                sl := rval.Slots[pidx]
                n := rval.Vars[pidx]
@@ -1948,3 +1954,19 @@ func BuildFuncDebugNoOptimized(ctxt *obj.Link, f *Func, loggingEnabled bool, sta
                pidx++
        }
 }
+
+// IsVarWantedForDebug returns true if the debug info for the node should
+// be generated.
+// For example, internal variables for range-over-func loops have little
+// value to users, so we don't generate debug info for them.
+func IsVarWantedForDebug(n ir.Node) bool {
+       name := n.Sym().Name
+       if len(name) > 0 && name[0] == '&' {
+               name = name[1:]
+       }
+       if len(name) > 0 && name[0] == '#' {
+               // #yield is used by delve.
+               return strings.HasPrefix(name, "#yield")
+       }
+       return true
+}