The following honors -frounding-math when converting a FP constant
to another FP type.
Bootstrapped and tested on x86_64-unknown-linux-gnu, OK?
I wonder what a good way to test this in a portable way, the bugreport
unfortunately didn't contain something executable and I don't see
much -frounding-math test coverage to copy from.
Thanks,
Richard.
2021-10-27 Richard Biener <rguent...@suse.de>
PR middle-end/57245
* fold-const.c (fold_convert_const_real_from_real): Honor
-frounding-math if the conversion is not exact.
---
gcc/fold-const.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index ff23f12f33c..c7aebf9cc7e 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 shuld 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);
--
2.31.1
