From: Roger Sayle Date: Mon, 3 Aug 2020 12:15:58 +0000 (+0100) Subject: PR rtl-optimization 61494: Preserve x-0.0 with HONOR_SNANS. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=919c9d4bd3db7da09061af3b6f2a9193bf7bae45;p=gcc.git PR rtl-optimization 61494: Preserve x-0.0 with HONOR_SNANS. The following patch avoids simplifying x-0.0 to x when -fsignaling-nans is specified, which resolves PR rtl-optimization 61494. Indeed, running the test program attached to that PR now reports no failures. 2020-08-02 Roger Sayle gcc/ChangeLog PR rtl-optimization/61494 * simplify-rtx.c (simplify_binary_operation_1) [MINUS]: Don't simplify x - 0.0 with -fsignaling-nans. --- diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index d2211686acc..4f0652f553e 100644 --- a/gcc/simplify-rtx.c +++ b/gcc/simplify-rtx.c @@ -2678,11 +2678,12 @@ simplify_binary_operation_1 (enum rtx_code code, machine_mode mode, && !contains_symbolic_reference_p (op1)) return simplify_gen_unary (NOT, mode, op1, mode); - /* Subtracting 0 has no effect unless the mode has signed zeros - and supports rounding towards -infinity. In such a case, - 0 - 0 is -0. */ + /* Subtracting 0 has no effect unless the mode has signalling NaNs, + or has signed zeros and supports rounding towards -infinity. + In such a case, 0 - 0 is -0. */ if (!(HONOR_SIGNED_ZEROS (mode) && HONOR_SIGN_DEPENDENT_ROUNDING (mode)) + && !HONOR_SNANS (mode) && trueop1 == CONST0_RTX (mode)) return op0;