| Summary: | [5 Regression] gcc miscompiles division of signed char | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Vsevolod Livinskii <vsevolod.livinskiy> |
| Component: | middle-end | Assignee: | Richard Biener <rguenth> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | jakub |
| Priority: | P2 | Keywords: | wrong-code |
| Version: | 7.0.1 | ||
| Target Milestone: | 6.4 | ||
| Host: | Target: | ||
| Build: | Known to work: | 6.3.1, 7.0.1 | |
| Known to fail: | 5.4.0, 6.3.0 | Last reconfirmed: | 2017-04-06 00:00:00 |
| Bug Depends on: | |||
| Bug Blocks: | 103035 | ||
| Attachments: | Reproducer. | ||
|
Description
Vsevolod Livinskii
2017-04-06 10:48:39 UTC
GCC 4.4 gives 90 but GCC 4.5 gives 1. Better testcase:
const signed char c = -84;
signed char s;
void
foo ()
{
s = (unsigned short) c / -55;
}
int
main ()
{
foo ();
if (s != 90)
__builtin_abort ();
}
Likely started with
commit 4d307e1ff39d0c2f90123ef789d611e2323be76d
Author: rguenth <rguenth@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Wed Feb 10 11:54:14 2010 +0000
2010-02-10 Richard Guenther <rguenther@suse.de>
PR c/43007
* tree.c (get_unwidened): Handle constants.
* convert.c (convert_to_integer): Handle TRUNC_DIV_EXPR.
* gcc.c-torture/execute/20100209-1.c: New testcase.
* gcc.dg/fold-div-3.c: Likewise.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@156653 138bc75d-0d04-0410-961f-82ee72b054a4
With -O I get
x.c: In function ‘foo’:
x.c:7:7: warning: overflow in implicit constant conversion [-Woverflow]
s = (unsigned short) c / -55;
^
hmm, get_unwidened ((int) (short unsigned int) c) returns c?! I wonder if that's by design... Ah, it is as we pass it signed char as 2nd arg... Testing patch. Author: rguenth Date: Fri Apr 7 08:20:24 2017 New Revision: 246756 URL: https://gcc.gnu.org/viewcvs?rev=246756&root=gcc&view=rev Log: 2017-04-07 Richard Biener <rguenther@suse.de> PR middle-end/80341 * tree.c (get_unwidened): Also handle ! for_type case for INTEGER_CSTs. * convert.c (do_narrow): Split out from ... (convert_to_integer_1): ... here. Do not pass final truncation type to get_unwidened for TRUNC_DIV_EXPR. * gcc.dg/torture/pr80341.c: New testcase. Added: trunk/gcc/testsuite/gcc.dg/torture/pr80341.c Modified: trunk/gcc/ChangeLog trunk/gcc/convert.c trunk/gcc/testsuite/ChangeLog trunk/gcc/tree.c Fixed on trunk sofar. Author: rguenth Date: Thu Jun 22 07:30:03 2017 New Revision: 249499 URL: https://gcc.gnu.org/viewcvs?rev=249499&root=gcc&view=rev Log: 2017-06-22 Richard Biener <rguenther@suse.de> Backport from mainline 2017-04-20 Richard Biener <rguenther@suse.de> PR tree-optimization/80453 * tree-ssa-sccvn.h (struct vn_phi_s): Add cclhs and ccrhs members. * tree-ssa-sccvn.c (cond_stmts_equal_p): Use recorded lhs and rhs from the conditions. (vn_phi_eq): Pass them down. (vn_phi_lookup): Record them. (vn_phi_insert): Likewise. 2017-04-07 Richard Biener <rguenther@suse.de> PR middle-end/80341 * tree.c (get_unwidened): Also handle ! for_type case for INTEGER_CSTs. * convert.c (do_narrow): Split out from ... (convert_to_integer_1): ... here. Do not pass final truncation type to get_unwidened for TRUNC_DIV_EXPR. * gcc.dg/torture/pr80341.c: New testcase. 2017-04-04 Richard Biener <rguenther@suse.de> PR middle-end/80281 * match.pd (A + (-B) -> A - B): Make sure to preserve unsigned arithmetic done for the negate or the plus. Simplify. (A - (-B) -> A + B): Likewise. * fold-const.c (split_tree): Make sure to not negate pointers. * gcc.dg/torture/pr80281.c: New testcase. Modified: branches/gcc-6-branch/gcc/ChangeLog branches/gcc-6-branch/gcc/convert.c branches/gcc-6-branch/gcc/fold-const.c branches/gcc-6-branch/gcc/match.pd branches/gcc-6-branch/gcc/testsuite/ChangeLog branches/gcc-6-branch/gcc/tree-ssa-sccvn.c branches/gcc-6-branch/gcc/tree-ssa-sccvn.h branches/gcc-6-branch/gcc/tree.c Author: rguenth Date: Mon Sep 18 11:10:06 2017 New Revision: 252920 URL: https://gcc.gnu.org/viewcvs?rev=252920&root=gcc&view=rev Log: 2017-09-18 Richard Biener <rguenther@suse.de> Backport from mainline 2017-04-07 Richard Biener <rguenther@suse.de> PR middle-end/80341 * gcc.dg/torture/pr80341.c: New testcase. 2017-04-04 Richard Biener <rguenther@suse.de> PR middle-end/80281 * gcc.dg/torture/pr80281.c: New testcase. Added: branches/gcc-6-branch/gcc/testsuite/gcc.dg/torture/pr80281.c branches/gcc-6-branch/gcc/testsuite/gcc.dg/torture/pr80341.c Modified: branches/gcc-6-branch/gcc/testsuite/ChangeLog GCC 5 branch has been closed, should be fixed in GCC 6.4 and later. |