Since the quiet NaN and signalling NaN representation on mips depends on the
CPU model, it can be expected that a compiler guesses it wrong. This means:
- The compiler's constant-folding of 0.0f/0.0f, 0.0/0.0, 0.0L/0.0L
produces a signalling NaN instead of quiet NaN. (This is the case on
OpenBSD 7.4/mips64.)
- The compiler's __builtin_nan{f,l} functions may produce a wrong result as
well (like they do now on sh4:
<https://gcc.gnu.org/bugzilla//show_bug.cgi?id=111814>).
2023-11-06 Bruno Haible <br...@clisp.org>
nan: Work around clang's incorrect constant-folding on mips64.
* lib/nan.h (NaNf, NaNd, NaNl): On mips platforms, avoid the compiler's
constant-folding for 0.0f/0.0f, 0.0/0.0, 0.0L/0.0L.
diff --git a/lib/nan.h b/lib/nan.h
index 4cb56350f8..219b25aeac 100644
--- a/lib/nan.h
+++ b/lib/nan.h
@@ -29,10 +29,11 @@
/* The Compaq (ex-DEC) C 6.4 compiler and the Microsoft MSVC 9 compiler choke
on the expression 0.0 / 0.0. The IBM XL C compiler on z/OS complains.
- PGI 16.10 complains. */
+ PGI 16.10 complains. clang 13 on mips64 does incorrect constant-folding.
*/
#if (defined __DECC || defined _MSC_VER \
- || (defined __MVS__ && defined __IBMC__) \
- || defined __PGI)
+ || (defined __MVS__ && defined __IBMC__) \
+ || defined __PGI \
+ || defined __mips__)
static float
NaNf ()
{
@@ -48,10 +49,11 @@ NaNf ()
/* The Compaq (ex-DEC) C 6.4 compiler and the Microsoft MSVC 9 compiler choke
on the expression 0.0 / 0.0. The IBM XL C compiler on z/OS complains.
- PGI 16.10 complains. */
+ PGI 16.10 complains. clang 13 on mips64 does incorrect constant-folding.
*/
#if (defined __DECC || defined _MSC_VER \
- || (defined __MVS__ && defined __IBMC__) \
- || defined __PGI)
+ || (defined __MVS__ && defined __IBMC__) \
+ || defined __PGI \
+ || defined __mips__)
static double
NaNd ()
{
@@ -69,14 +71,18 @@ NaNd ()
runtime type conversion.
The Microsoft MSVC 9 compiler chokes on the expression 0.0L / 0.0L.
The IBM XL C compiler on z/OS complains.
- PGI 16.10 complains. */
+ PGI 16.10 complains.
+ Avoid possible incorrect constant-folding on mips. */
#ifdef __sgi
static long double NaNl ()
{
double zero = 0.0;
return zero / zero;
}
-#elif defined _MSC_VER || (defined __MVS__ && defined __IBMC__) || defined
__PGI
+#elif (defined _MSC_VER \
+ || (defined __MVS__ && defined __IBMC__) \
+ || defined __PGI \
+ || defined __mips__)
static long double
NaNl ()
{
