Hi,
In function fold_convert_const_real_from_real, when the modes of
two types involved in fp conversion are the same, we can simply
take it as copy, rebuild with the exactly same TREE_REAL_CST and
the target type. It is more efficient and helps to avoid possible
unexpected signalling bit clearing in [1].
Bootstrapped and regtested on x86_64-redhat-linux, aarch64-linux-gnu
and powerpc64{,le}-linux-gnu.
Is it ok for trunk?
[1] https://gcc.gnu.org/pipermail/gcc-patches/2022-December/608533.html
gcc/ChangeLog:
* fold-const.cc (fold_convert_const_real_from_real): Treat floating
point conversion to a type with same mode as copy instead of normal
convertFormat.
---
gcc/fold-const.cc | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 114258fa182..eb4b6ca8820 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -2178,6 +2178,15 @@ fold_convert_const_real_from_real (tree type, const_tree
arg1)
REAL_VALUE_TYPE value;
tree t;
+ /* If the underlying modes are the same, simply treat it as
+ copy and rebuild with TREE_REAL_CST information and the
+ given type. */
+ if (TYPE_MODE (type) == TYPE_MODE (TREE_TYPE (arg1)))
+ {
+ t = build_real (type, TREE_REAL_CST (arg1));
+ return t;
+ }
+
/* Don't perform the operation if flag_signaling_nans is on
and the operand is a signaling NaN. */
if (HONOR_SNANS (arg1)
--
2.27.0
