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[PATCH] Don't forwprop into clobbers in some cases (PR tree-optimization/56854)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Richard Biener <rguenther at suse dot de>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Mon, 8 Apr 2013 21:23:47 +0200
- Subject: [PATCH] Don't forwprop into clobbers in some cases (PR tree-optimization/56854)
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
lhs ={v} {CLOBBER};
stmts right now allow only VAR_DECL or MEM_REF lhs, but the forwprop code
below on the attached testcase attempts to propagate an ARRAY_REF (of
MEM_REF) into it. Fixed by not propagating in that case, allowing arbitrary
memory lhs is IMHO unnecessary and such lhs's wouldn't be very useful for
DSE anyway.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2013-04-08 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/56854
* tree-ssa-forwprop.c (forward_propagate_addr_expr_1): Don't
forward into clobber stmts if it would change MEM_REF lhs into
non-MEM_REF.
* g++.dg/torture/pr56854.C: New test.
--- gcc/tree-ssa-forwprop.c.jj 2013-02-25 23:51:21.000000000 +0100
+++ gcc/tree-ssa-forwprop.c 2013-04-08 16:12:37.000000000 +0200
@@ -826,7 +826,11 @@ forward_propagate_addr_expr_1 (tree name
&& integer_zerop (TREE_OPERAND (lhs, 1))
&& useless_type_conversion_p
(TREE_TYPE (TREE_OPERAND (def_rhs, 0)),
- TREE_TYPE (gimple_assign_rhs1 (use_stmt))))
+ TREE_TYPE (gimple_assign_rhs1 (use_stmt)))
+ /* Don't forward anything into clobber stmts if it would result
+ in the lhs no longer being a MEM_REF. */
+ && (!gimple_clobber_p (use_stmt)
+ || TREE_CODE (TREE_OPERAND (def_rhs, 0)) == MEM_REF))
{
tree *def_rhs_basep = &TREE_OPERAND (def_rhs, 0);
tree new_offset, new_base, saved, new_lhs;
--- gcc/testsuite/g++.dg/torture/pr56854.C.jj 2013-04-08 18:03:37.978009666 +0200
+++ gcc/testsuite/g++.dg/torture/pr56854.C 2013-04-08 18:03:09.000000000 +0200
@@ -0,0 +1,24 @@
+// PR tree-optimization/56854
+// { dg-do compile }
+
+inline void *
+operator new (__SIZE_TYPE__, void *p) throw ()
+{
+ return p;
+}
+
+struct A
+{
+ int a;
+ A () : a (0) {}
+ ~A () {}
+ A &operator= (const A &v) { this->~A (); new (this) A (v); return *this; }
+};
+A b[4], c[4];
+
+void
+foo ()
+{
+ for (int i = 0; i < 4; ++i)
+ c[i] = b[i];
+}
Jakub