https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96392
--- Comment #1 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:5b02ed4b87685c0f7c5da9b46cde3ce56fcfd457 commit r12-1393-g5b02ed4b87685c0f7c5da9b46cde3ce56fcfd457 Author: Roger Sayle <ro...@nextmovesoftware.com> Date: Fri Jun 11 17:15:38 2021 +0100 [PATCH] PR tree-optimization/96392 Optimize x+0.0 if x is an integer The patch implements a missed optimization enhancement. Under usual IEEE rules, x+0.0 can't be simplified to x when x might potentially be an IEEE minus zero (-0.0). The current logic in the middle-end checks whether the type of x should honor signed zeros, but with this patch we introduce tree_expr_maybe_real_minus_zero_p that allows us to confirm that the value can't possibly be -0.0, for example, the result of a conversion from an integer type, or the result of fabs (or has a type that doesn't honor signed zero). Whilst modifying match.pd, I also converted some additional folding transformations from "testing the type" to "testing the value". 2020-06-10 Roger Sayle <ro...@nextmovesoftware.com> gcc/ChangeLog PR tree-optimization/96392 * fold-const.c (fold_real_zero_addition_p): Take both arguments of the addition or subtraction, not just the zero. Use this other argument in tests for signaling NaNs and signed zeros. (tree_expr_maybe_real_minus_zero_p): New predicate. * fold-const.h (fold_real_zero_addition_p): Update prototype. (tree_expr_maybe_real_minus_zero_p): New function prototype. * match.pd: Update calls to fold_real_zero_addition_p. Replace HONOR_NANS with tree_expr_maybe_nan_p. Replace HONOR_SIGNED_ZEROS with tree_expr_maybe_real_minus_zero_p. Replace HONOR_SNANS with tree_expr_maybe_signaling_nan_p. * tree-ssa-reassoc.c (eliminate_using_constants): Update call to fold_real_zero_addition_p. gcc/testsuite/ChangeLog PR tree-optimization/96392 * gcc.dg/pr96392.c: New test.
