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[PATCH] Fix endless recursion in BIT_AND_EXPR folding (PR middle-end/40204)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Wed, 20 May 2009 23:01:45 +0200
- Subject: [PATCH] Fix endless recursion in BIT_AND_EXPR folding (PR middle-end/40204)
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
On the attached testcase we endlessly recurse between fold_binary
(BIT_AND_EXPR, ...) and fold_build2 (BIT_AND_EXPR, ...). The problem
is in the PR29749 optimization, if op1 has a smaller precision type,
newmask might be different from mask, yet build_int_cst_type
might strip the extra bits again, yielding identical constant as arg1.
Fixed by checking for this and not recursing in that case.
Bootstrapped/regtested on x86_64-linux, ok for trunk/4.4?
2009-05-20 Jakub Jelinek <jakub@redhat.com>
PR middle-end/40204
* fold-const.c (fold_binary) <case BIT_AND_EXPR>: Avoid infinite
recursion if build_int_cst_type returns the same INTEGER_CST as
arg1.
* gcc.c-torture/compile/pr40204.c: New test.
--- gcc/fold-const.c.jj 2009-05-19 10:51:32.000000000 +0200
+++ gcc/fold-const.c 2009-05-20 18:18:04.000000000 +0200
@@ -11375,6 +11375,8 @@ fold_binary (enum tree_code code, tree t
if (prec < HOST_BITS_PER_WIDE_INT
|| newmask == ~(unsigned HOST_WIDE_INT) 0)
{
+ tree newmaskt;
+
if (shift_type != TREE_TYPE (arg0))
{
tem = fold_build2 (TREE_CODE (arg0), shift_type,
@@ -11385,9 +11387,9 @@ fold_binary (enum tree_code code, tree t
}
else
tem = op0;
- return fold_build2 (BIT_AND_EXPR, type, tem,
- build_int_cst_type (TREE_TYPE (op1),
- newmask));
+ newmaskt = build_int_cst_type (TREE_TYPE (op1), newmask);
+ if (!tree_int_cst_equal (newmaskt, arg1))
+ return fold_build2 (BIT_AND_EXPR, type, tem, newmaskt);
}
}
}
--- gcc/testsuite/gcc.c-torture/compile/pr40204.c.jj 2009-05-20 18:20:41.000000000 +0200
+++ gcc/testsuite/gcc.c-torture/compile/pr40204.c 2009-05-20 18:20:19.000000000 +0200
@@ -0,0 +1,14 @@
+/* PR middle-end/40204 */
+
+struct S
+{
+ unsigned int a : 4;
+ unsigned int b : 28;
+} s;
+char c;
+
+void
+f (void)
+{
+ s.a = (c >> 4) & ~(1 << 4);
+}
Jakub