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From: Richard Biener <rguenth@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r12-4764] middle-end/57245 - honor -frounding-math in real truncation Date: Thu, 28 Oct 2021 09:29:01 +0000 (GMT) [thread overview] Message-ID: <20211028092901.43ED43858404@sourceware.org> (raw) https://gcc.gnu.org/g:a84b9d5373c7e67fd0ab2a412c22162cdf969c91 commit r12-4764-ga84b9d5373c7e67fd0ab2a412c22162cdf969c91 Author: Richard Biener <rguenther@suse.de> Date: Wed Oct 27 14:27:40 2021 +0200 middle-end/57245 - honor -frounding-math in real truncation The following honors -frounding-math when converting a FP constant to another FP type. 2021-10-27 Richard Biener <rguenther@suse.de> PR middle-end/57245 * fold-const.c (fold_convert_const_real_from_real): Honor -frounding-math if the conversion is not exact. * simplify-rtx.c (simplify_const_unary_operation): Do not simplify FLOAT_TRUNCATE with sign dependent rounding. * gcc.dg/torture/fp-double-convert-float-1.c: New testcase. Diff: --- gcc/fold-const.c | 6 ++++ gcc/simplify-rtx.c | 5 +++ .../gcc.dg/torture/fp-double-convert-float-1.c | 41 ++++++++++++++++++++++ 3 files changed, 52 insertions(+) diff --git a/gcc/fold-const.c b/gcc/fold-const.c index ff23f12f33c..18950aeb760 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -2139,6 +2139,12 @@ fold_convert_const_real_from_real (tree type, const_tree arg1) && REAL_VALUE_ISSIGNALING_NAN (TREE_REAL_CST (arg1))) return NULL_TREE; + /* With flag_rounding_math we should respect the current rounding mode + unless the conversion is exact. */ + if (HONOR_SIGN_DEPENDENT_ROUNDING (arg1) + && !exact_real_truncate (TYPE_MODE (type), &TREE_REAL_CST (arg1))) + return NULL_TREE; + real_convert (&value, TYPE_MODE (type), &TREE_REAL_CST (arg1)); t = build_real (type, value); diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index bbbd6b74942..f38b6d7d31c 100644 --- a/gcc/simplify-rtx.c +++ b/gcc/simplify-rtx.c @@ -2068,6 +2068,11 @@ simplify_const_unary_operation (enum rtx_code code, machine_mode mode, and the operand is a signaling NaN. */ if (HONOR_SNANS (mode) && REAL_VALUE_ISSIGNALING_NAN (d)) return NULL_RTX; + /* Or if flag_rounding_math is on and the truncation is not + exact. */ + if (HONOR_SIGN_DEPENDENT_ROUNDING (mode) + && !exact_real_truncate (mode, &d)) + return NULL_RTX; d = real_value_truncate (mode, d); break; case FLOAT_EXTEND: diff --git a/gcc/testsuite/gcc.dg/torture/fp-double-convert-float-1.c b/gcc/testsuite/gcc.dg/torture/fp-double-convert-float-1.c new file mode 100644 index 00000000000..ec23274ea98 --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/fp-double-convert-float-1.c @@ -0,0 +1,41 @@ +/* PR57245 */ +/* { dg-do run } */ +/* { dg-require-effective-target fenv } */ +/* { dg-additional-options "-frounding-math" } */ + +#include <fenv.h> +#include <stdlib.h> + +int +main () +{ +#if __DBL_MANT_DIG__ == 53 && __FLT_MANT_DIG__ == 24 +#ifdef FE_UPWARD + fesetround (FE_UPWARD); + float f = 1.3; + if (f != 0x1.4ccccep+0f) + __builtin_abort (); +#endif +#ifdef FE_TONEAREST + fesetround (FE_TONEAREST); + /* Use different actual values so the bogus CSE we perform does not + break things. */ + f = 1.33; + if (f != 0x1.547ae2p+0f) + abort (); +#endif +#ifdef FE_DOWNWARD + fesetround (FE_DOWNWARD); + f = 1.333; + if (f != 0x1.553f7cp+0f) + abort (); +#endif +#ifdef FE_TOWARDZERO + fesetround (FE_TOWARDZERO); + f = 1.3333; + if (f != 0x1.555326p+0f) + abort (); +#endif +#endif + return 0; +}
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