ssa: switch lblocks to types.Object

Switches lblocks from *ast.Object to types.Object. Removes a user from the infrequently used *ast.Object.

Updates golang/go#52463

Change-Id: I1a21ab55b7136f4891f6aa2f76459880ace389c9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/402034
Reviewed-by: Dominik Honnef <dominik@honnef.co>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Tim King <taking@google.com>
Reviewed-by: Zvonimir Pavlinovic <zpavlinovic@google.com>

go/ssa/func.go

@@ -74,13 +74,14 @@ type lblock struct {
 // labelledBlock returns the branch target associated with the
 // specified label, creating it if needed.
 func (f *Function) labelledBlock(label *ast.Ident) *lblock {
-	lb := f.lblocks[label.Obj]
+	obj := f.objectOf(label)
+	lb := f.lblocks[obj]
 	if lb == nil {
 		lb = &lblock{_goto: f.newBasicBlock(label.Name)}
 		if f.lblocks == nil {
-			f.lblocks = make(map[*ast.Object]*lblock)
+			f.lblocks = make(map[types.Object]*lblock)
 		}
-		f.lblocks[label.Obj] = lb
+		f.lblocks[obj] = lb
 	}
 	return lb
 }

go/ssa/ssa.go

@@ -331,13 +331,13 @@ type Function struct {
 
 	// The following fields are set transiently during building,
 	// then cleared.
-	currentBlock *BasicBlock             // where to emit code
-	objects      map[types.Object]Value  // addresses of local variables
-	namedResults []*Alloc                // tuple of named results
-	targets      *targets                // linked stack of branch targets
-	lblocks      map[*ast.Object]*lblock // labelled blocks
-	info         *types.Info             // *types.Info to build from. nil for wrappers.
-	subst        *subster                // type substitution cache
+	currentBlock *BasicBlock              // where to emit code
+	objects      map[types.Object]Value   // addresses of local variables
+	namedResults []*Alloc                 // tuple of named results
+	targets      *targets                 // linked stack of branch targets
+	lblocks      map[types.Object]*lblock // labelled blocks
+	info         *types.Info              // *types.Info to build from. nil for wrappers.
+	subst        *subster                 // type substitution cache
 }
 
 // BasicBlock represents an SSA basic block.