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Re: c/8639: [3.2/3.3 regression] simple integer arithmetic expression broken
- From: "Christian Ehrhardt" <ehrhardt at mathematik dot uni-ulm dot de>
- To: gcc-gnats at gcc dot gnu dot org, gcc-prs at gcc dot gnu dot org, steveJepsen at netscape dot net, gcc-bugs at gcc dot gnu dot org, nobody at gcc dot gnu dot org
- Date: Tue, 19 Nov 2002 19:09:59 +0100
- Subject: Re: c/8639: [3.2/3.3 regression] simple integer arithmetic expression broken
Hi,
this patch will be bootstrapping here in a minute. An non bootstapped
compile indicates that this fixes the bug. I'm not sure if we can be
more clever here without doing a big rewrite of fold-const.c. I'll
report back tonight/tomorrow (CET) when the testsuite has completed.
Someone please consider to check this in. I don't have CVS access.
Also adding a testcase would probably be a good idea.
regards Christian
--- gcc-3.2.1-20021111/gcc/fold-const.c.orig Tue Nov 19 18:47:57 2002
+++ gcc-3.2.1-20021111/gcc/fold-const.c Tue Nov 19 18:57:04 2002
@@ -4617,10 +4617,12 @@
t2 = extract_muldiv (op1, c, code, wide_type);
if (t1 != 0 && t2 != 0
&& (code == MULT_EXPR
- /* If not multiplication, we can only do this if either operand
- is divisible by c. */
- || multiple_of_p (ctype, op0, c)
- || multiple_of_p (ctype, op1, c)))
+ /* If not multiplication, we can only do this if this is
+ * PLUS_EXPR and both operands are divisible by c. Note that
+ * (80 - 4*x)/20 or (80 + (-4)*x)/20 must not degenerate
+ * into (20 - x/5). */
+ || (multiple_of_p (ctype, op0, c) &&
+ multiple_of_p (ctype, op1, c))))
return fold (build (tcode, ctype, convert (ctype, t1),
convert (ctype, t2)));
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8639
--
THAT'S ALL FOLKS!