https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98865
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Roger Sayle <sa...@gcc.gnu.org>: https://gcc.gnu.org/g:8f571e64713cc72561f84241863496e473eae4c6 commit r12-3824-g8f571e64713cc72561f84241863496e473eae4c6 Author: Roger Sayle <ro...@nextmovesoftware.com> Date: Wed Sep 22 19:17:49 2021 +0100 More NEGATE_EXPR folding in match.pd As observed by Jakub in comment #2 of PR 98865, the expression -(a>>63) is optimized in GENERIC but not in GIMPLE. Investigating further it turns out that this is one of a few transformations performed by fold_negate_expr in fold-const.c that aren't yet performed by match.pd. This patch moves/duplicates them there, and should be relatively safe as these transformations are already performed by the compiler, but just in different passes. This revised patch adds a Boolean simplify argument to tree-ssa-sccvn.c's vn_nary_build_or_lookup_1 to control whether simplification should be performed before value numbering, updating the callers, but then avoiding simplification when constructing/value-numbering NEGATE_EXPR. This avoids the regression of gcc.dg/tree-ssa/ssa-free-88.c, and enables the new test case(s) to pass. 2021-09-22 Roger Sayle <ro...@nextmovesoftware.com> Richard Biener <rguent...@suse.de> gcc/ChangeLog * match.pd (negation simplifications): Implement some negation folding transformations from fold-const.c's fold_negate_expr. * tree-ssa-sccvn.c (vn_nary_build_or_lookup_1): Add a SIMPLIFY argument, to control whether the op should be simplified prior to looking up/assigning a value number. (vn_nary_build_or_lookup): Update call to vn_nary_build_or_lookup_1. (vn_nary_simplify): Likewise. (visit_nary_op): Likewise, but when constructing a NEGATE_EXPR now call vn_nary_build_or_lookup_1 disabling simplification. gcc/testsuite/ChangeLog * gcc.dg/fold-negate-1.c: New test case.
