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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/97457] [10/11 Regression] SVE: wrong code since r10-4752-g2d56600c Date: Wed, 28 Oct 2020 19:06:16 +0000 [thread overview] Message-ID: <bug-97457-4-w4pmFmsLvc@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-97457-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97457 --- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Richard Sandiford <rsandifo@gcc.gnu.org>: https://gcc.gnu.org/g:54ef7701a9dec8c923a12d1983f8a051ba88a7b9 commit r11-4495-g54ef7701a9dec8c923a12d1983f8a051ba88a7b9 Author: Richard Sandiford <richard.sandiford@arm.com> Date: Wed Oct 28 19:05:49 2020 +0000 value-range: Give up on POLY_INT_CST ranges [PR97457] This PR shows another problem with calculating value ranges for POLY_INT_CSTs. We have: ivtmp_76 = ASSERT_EXPR <ivtmp_60, ivtmp_60 > POLY_INT_CST [9, 4294967294]> where the VQ coefficient is unsigned but is effectively acting as a negative number. We wrongly give the POLY_INT_CST the range: [9, INT_MAX] and things go downhill from there: later iterations of the unrolled epilogue are wrongly removed as dead. I guess this is the final nail in the coffin for doing VRP on POLY_INT_CSTs. For other similarly exotic testcases we could have overflow for any coefficient, not just those that could be treated as contextually negative. Testing TYPE_OVERFLOW_UNDEFINED doesn't seem like an option because we couldn't handle warn_strict_overflow properly. At this stage we're just recording a range that might or might not lead to strict-overflow assumptions later. It still feels like we should be able to do something here, but for now removing the code seems safest. It's also telling that there are no testsuite failures on SVE from doing this. gcc/ PR tree-optimization/97457 * value-range.cc (irange::set): Don't decay POLY_INT_CST ranges to integer ranges. gcc/testsuite/ PR tree-optimization/97457 * gcc.dg/vect/pr97457.c: New test.
next prev parent reply other threads:[~2020-10-28 19:06 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-16 11:51 [Bug target/97457] New: " acoplan at gcc dot gnu.org 2020-10-16 11:52 ` [Bug target/97457] " acoplan at gcc dot gnu.org 2020-10-16 11:57 ` acoplan at gcc dot gnu.org 2020-10-16 15:25 ` acoplan at gcc dot gnu.org 2020-10-27 17:35 ` rsandifo at gcc dot gnu.org 2020-10-28 19:06 ` cvs-commit at gcc dot gnu.org [this message] 2020-12-02 18:39 ` [Bug target/97457] [10 " cvs-commit at gcc dot gnu.org 2020-12-02 18:42 ` rsandifo at gcc dot gnu.org 2020-12-30 14:41 ` rsandifo at gcc dot gnu.org
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