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[Bug tree-optimization/32544] gcc 4.2.1 miscompiles Mesa's r300 DRI driver with -ftree-vrp
- From: "pixel at mandriva dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 7 Aug 2007 22:41:20 -0000
- Subject: [Bug tree-optimization/32544] gcc 4.2.1 miscompiles Mesa's r300 DRI driver with -ftree-vrp
- References: <bug-32544-5606@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #6 from pixel at mandriva dot com 2007-08-07 22:41 -------
more info: the tree-vrp issue is raised by ivopts pass:
without ivopts:
D.1541_13 = 3 - i_31;
D.1542_14 = (unsigned int) D.1541_13;
D.1543_15 = D.1542_14 * 4;
D.1544_16 = (int *) D.1543_15;
with ivopts:
D.1607_62 = (int *) i_31;
D.1608_63 = D.1607_62 * -4B;
D.1544_64 = D.1608_63 + 12B;
D.1544_16 = D.1544_64;
vrp finds that D.1608_63 is 0, and so replaces D.1544_64 with 12
D.1607_62 = (int *) i_31;
D.1608_63 = D.1607_62 * -4B;
D.1544_64 = D.1608_63 + 12B;
D.1544_16 = D.1544_64;
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32544