defer: enable loop lowering

ssa/stmt_builder.go

@@ -57,11 +57,6 @@ func (p BasicBlock) Addr() Expr {
 
 // -----------------------------------------------------------------------------
 
-type dbgExpr struct {
-	ptr Expr
-	val Expr
-}
-
 type aBuilder struct {
 	impl llvm.Builder
 	blk  BasicBlock
@@ -69,7 +64,6 @@ type aBuilder struct {
 	Pkg  Package
 	Prog Program
 
-	dbgVars      map[Expr]dbgExpr         // save copied address and values for debug info
 	diScopeCache map[*types.Scope]DIScope // avoid duplicated DILexicalBlock(s)
 }