* C++/gimplify PATCH for c++/45307 (store of empty class not removed in gimplification)
@ 2010-08-19 17:23 Jason Merrill
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From: Jason Merrill @ 2010-08-19 17:23 UTC (permalink / raw)
To: gcc-patches List
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The code in cp-gimplify for eliminating empty stores didn't get a chance
to remove this one because gimplify_init_constructor moved it into the
pre-queue. Fixed thus.
Tested x86_64-pc-linux-gnu, applied to trunk.
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commit 6edaaca64b5498d9c3b267cb0d60d70d801b5dd5
Author: Jason Merrill <jason@redhat.com>
Date: Tue Aug 17 14:51:04 2010 -0400
PR c++/45307
* gimplify.c (gimplify_init_constructor): Just return GS_UNHANDLED
if ctor is empty.
(gimplify_modify_expr_rhs): Adjust.
diff --git a/gcc/cp/cp-gimplify.c b/gcc/cp/cp-gimplify.c
index abd5bf3..e5a7f26 100644
--- a/gcc/cp/cp-gimplify.c
+++ b/gcc/cp/cp-gimplify.c
@@ -575,15 +575,18 @@ cp_gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
TREE_OPERAND (*expr_p, 1) = build1 (VIEW_CONVERT_EXPR,
TREE_TYPE (op0), op1);
- else if ((is_gimple_lvalue (op1) || INDIRECT_REF_P (op1))
- && !(TREE_CODE (op1) == CALL_EXPR
- && CALL_EXPR_RETURN_SLOT_OPT (op1))
+ else if ((is_gimple_lvalue (op1) || INDIRECT_REF_P (op1)
+ || (TREE_CODE (op1) == CONSTRUCTOR
+ && CONSTRUCTOR_NELTS (op1) == 0)
+ || (TREE_CODE (op1) == CALL_EXPR
+ && !CALL_EXPR_RETURN_SLOT_OPT (op1)))
&& is_really_empty_class (TREE_TYPE (op0)))
{
/* Remove any copies of empty classes. We check that the RHS
- has a simple form so that TARGET_EXPRs and CONSTRUCTORs get
- reduced properly, and we leave the return slot optimization
- alone because it isn't a copy.
+ has a simple form so that TARGET_EXPRs and non-empty
+ CONSTRUCTORs get reduced properly, and we leave the return
+ slot optimization alone because it isn't a copy (FIXME so it
+ shouldn't be represented as one).
Also drop volatile variables on the RHS to avoid infinite
recursion from gimplify_expr trying to load the value. */
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 8b97ee3..7e33666 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -4237,6 +4237,10 @@ gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p,
break;
case CONSTRUCTOR:
+ /* If we already made some changes, let the front end have a
+ crack at this before we break it down. */
+ if (ret != GS_UNHANDLED)
+ break;
/* If we're initializing from a CONSTRUCTOR, break this into
individual MODIFY_EXPRs. */
return gimplify_init_constructor (expr_p, pre_p, post_p, want_value,
diff --git a/gcc/testsuite/g++.dg/tree-ssa/empty-2.C b/gcc/testsuite/g++.dg/tree-ssa/empty-2.C
new file mode 100644
index 0000000..728678a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/empty-2.C
@@ -0,0 +1,8 @@
+// PR c++/45307
+// { dg-options -fdump-tree-gimple }
+
+struct fallible_t { };
+const fallible_t fallible = fallible_t();
+
+// { dg-final { scan-tree-dump-not "fallible" "gimple" } }
+// { dg-final { cleanup-tree-dump "gimple" } }
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