https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98256
--- Comment #1 from CVS Commits ---
The master branch has been updated by Jakub Jelinek :
https://gcc.gnu.org/g:49ec63666e086853401021e686f0aa4d285ce9dc
commit r11-5974-g49ec63666e086853401021e686f0aa4d285ce9dc
Author: Jakub Jelinek
Date: Sun Dec 13 19:25:33 2020 +0100
widening_mul: Fix a > ~b to .ADD_OVERFLOW optimization [PR98256]
Unfortunately, my latest tree-ssa-math-opts.c patch broke the following
testcase. The problem is that the code is adding .ADD_OVERFLOW or
.SUB_OVERFLOW before or after the stmt on which the function has been
called, which is normally a addition or subtraction that has all the
operands.
But in the a > ~b optimization that stmt is the ~b stmt and the other
comparison operand might be defined only after that ~b stmt, so we can't
insert the .ADD_OVERFLOW next to ~b that we want to delete, but need to
insert it before the a > temp comparison that uses it; and in that case
when removing the BIT_NOT_EXPR stmt we need to ensure the caller doesn't do
gsi_next because gsi_remove already points the iterator to the next stmt.
2020-12-13 Jakub Jelinek
PR tree-optimization/98256
* tree-ssa-math-opts.c (match_uaddsub_overflow): For BIT_NOT_EXPR,
only handle a single use, and insert .ADD_OVERFLOW before the
comparison rather than after the BIT_NOT_EXPR. Return true iff
it is BIT_NOT_EXPR and it has been removed.
(math_opts_dom_walker::after_dom_children) :
If match_uaddsub_overflow returned true, continue instead of break.
* gcc.c-torture/compile/pr98256.c: New test.
