cmd/compile: emit DWARF info about dictionary entries

When emitting the DIE of the instantiation of a generic function also
emit one DW_TAG_typedef_type entry for each dictionary entry in use,
referencing the shape type and having a custom attribute containing the
index inside the dictionary.

When emitting the DIE of variables that have an instantiated parametric
type, instead of referencing the shape type directly go through the
DW_TAG_typedef_type entry emitted for the dictionary entry describing
the real type of the variable.

Change-Id: Ia45d157ecd4c25e2b60300469e43bbb27a663582
Reviewed-on: https://go-review.googlesource.com/c/go/+/344929
Run-TryBot: Alessandro Arzilli <alessandro.arzilli@gmail.com>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Trust: Dan Scales <danscales@google.com>
Trust: Jeremy Faller <jeremy@golang.org>

1 files changed, 14 insertions, 4 deletions

diff --git a/src/cmd/compile/internal/noder/stencil.go b/src/cmd/compile/internal/noder/stencil.go
index 5069db9fe1..6c990c1828 100644
--- a/src/cmd/compile/internal/noder/stencil.go
+++ b/src/cmd/compile/internal/noder/stencil.go
@@ -779,6 +779,7 @@ func (subst *subster) localvar(name *ir.Name) *ir.Name {
 	m.Func = name.Func
 	subst.ts.Vars[name] = m
 	m.SetTypecheck(1)
+	m.DictIndex = name.DictIndex
 	if name.Defn != nil {
 		if name.Defn.Op() == ir.ONAME {
 			// This is a closure variable, so its Defn is the outer
@@ -1268,14 +1269,18 @@ func (subst *subster) node(n ir.Node) ir.Node {
 // function info.gfInfo. This will indicate the dictionary entry with the
 // correct concrete type for the associated instantiated function.
 func findDictType(info *instInfo, t *types.Type) int {
-	for i, dt := range info.gfInfo.tparams {
+	return info.gfInfo.findDictType(t)
+}
+
+func (gfInfo *gfInfo) findDictType(t *types.Type) int {
+	for i, dt := range gfInfo.tparams {
 		if dt == t {
 			return i
 		}
 	}
-	for i, dt := range info.gfInfo.derivedTypes {
+	for i, dt := range gfInfo.derivedTypes {
 		if types.Identical(dt, t) {
-			return i + len(info.gfInfo.tparams)
+			return i + len(gfInfo.tparams)
 		}
 	}
 	return -1
@@ -1736,6 +1741,7 @@ func (g *irgen) getGfInfo(gn *ir.Name) *gfInfo {
 
 	for _, n := range gf.Dcl {
 		addType(&info, n, n.Type())
+		n.DictIndex = uint16(info.findDictType(n.Type()) + 1)
 	}
 
 	if infoPrintMode {
@@ -1805,9 +1811,13 @@ func (g *irgen) getGfInfo(gn *ir.Name) *gfInfo {
 			// Visit the closure body and add all relevant entries to the
 			// dictionary of the outer function (closure will just use
 			// the dictionary of the outer function).
-			for _, n1 := range n.(*ir.ClosureExpr).Func.Body {
+			cfunc := n.(*ir.ClosureExpr).Func
+			for _, n1 := range cfunc.Body {
 				ir.Visit(n1, visitFunc)
 			}
+			for _, n := range cfunc.Dcl {
+				n.DictIndex = uint16(info.findDictType(n.Type()) + 1)
+			}
 		}
 		if n.Op() == ir.OSWITCH && n.(*ir.SwitchStmt).Tag != nil && n.(*ir.SwitchStmt).Tag.Op() == ir.OTYPESW && !n.(*ir.SwitchStmt).Tag.(*ir.TypeSwitchGuard).X.Type().IsEmptyInterface() {
 			for _, cc := range n.(*ir.SwitchStmt).Cases {