From 5b02ed4b87685c0f7c5da9b46cde3ce56fcfd457 Mon Sep 17 00:00:00 2001 From: Roger Sayle Date: Fri, 11 Jun 2021 17:15:38 +0100 Subject: [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 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. --- gcc/tree-ssa-reassoc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'gcc/tree-ssa-reassoc.c') diff --git a/gcc/tree-ssa-reassoc.c b/gcc/tree-ssa-reassoc.c index 6dfc703..2dd4435 100644 --- a/gcc/tree-ssa-reassoc.c +++ b/gcc/tree-ssa-reassoc.c @@ -1062,7 +1062,7 @@ eliminate_using_constants (enum tree_code opcode, if (integer_zerop (oelast->op) || (FLOAT_TYPE_P (type) && (opcode == PLUS_EXPR || opcode == MINUS_EXPR) - && fold_real_zero_addition_p (type, oelast->op, + && fold_real_zero_addition_p (type, 0, oelast->op, opcode == MINUS_EXPR))) { if (ops->length () != 1) -- cgit v1.1