gnu /
gcc /
8f571e64713cc72561f84241863496e473eae4c6 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 <roger@nextmovesoftware.com>
Richard Biener <rguenther@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.
3 files changed
