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testsuite failures on i586-pc-linux-gnu
- From: "Eric Botcazou" <ebotcazou at libertysurf dot fr>
- To: <gcc at gcc dot gnu dot org>
- Date: Sat, 11 May 2002 00:20:38 +0200
- Subject: testsuite failures on i586-pc-linux-gnu
Hello,
For some time the gcc testsuite has been showing some failures on
i586-pc-linux-gnu:
http://gcc.gnu.org/ml/gcc-testresults/2002-05/msg00229.html
The two following failures are identical:
FAIL: gcc.c-torture/execute/loop-2c.c execution, -Os
FAIL: gcc.c-torture/execute/loop-2d.c execution, -Os
They are triggered by a mis-optimization of the loop:
unsigned int i;
for (p = &a[b], i = b; --i < ~0; )
*--p = i * 3 + o;
The loop optimizer eliminates the basic induction variable i and replaces
the test --i < ~0 by a test on p. Now the initial test relies on i wrapping
around, so it is actually a GT test, not a LT, but the optimizer doesn't see
it.
Should the loop optimizer be taught not to eliminate the biv in that case or
the two tests be corrected ?
--
Eric Botcazou
ebotcazou@multimania.com