PR target/107299: Fix build issue when long double is IEEE 128-bit
Commit Message
This patch updates the IEEE 128-bit types used in libgcc.
At the moment, we cannot build GCC when the target uses IEEE 128-bit long
doubles, such as building the compiler for a native Fedora 36 system. The
build dies when it is trying to build the _mulkc3.c and _divkc3 modules.
This patch changes libgcc to use long double for the IEEE 128-bit base type if
long double is IEEE 128-bit, and it uses _Float128 otherwise. The built-in
functions are adjusted to be the correct version based on the IEEE 128-bit base
type used.
While it is desirable to ultimately have __float128 and _Float128 use the same
internal type and mode within GCC, at present if you use the option
-mabi=ieeelongdouble, the __float128 type will use the long double type and not
the _Float128 type. We get an internal compiler error if we combine the
signbitf128 built-in with a long double type.
I've gone through several iterations of trying to fix this within GCC, and
there are various problems that have come up. I developed this alternative
patch that changes libgcc so that it does not tickle the issue. I hope we can
fix the compiler at some point, but right now, this is preventing people on
Fedora 36 systems from building compilers where the default long double is IEEE
128-bit.
I have built a GCC compiler tool chain on the following platforms and there
were no regressions caused by these patches.
* Power10 little endian, IBM long double, --with-cpu=power10
* Power9 little endian, IBM long double, --with-cpu=power9
* Power8 big endian, IBM long double, --with-cpu=power8, both
32-bit/64-bit tests.
In addition, I have built a GCC compiler tool chain on the following systems
with IEEE 128-bit long double as the default. Comparing the test suite runs to
the runs for the toolchain with IBM long double as the default, I only get the
expected differences (C++ modules test fail on IEEE long double, 3 Fortran
tests pass on IEEE long double that fail on IBM long double, C test pr105334.c
fails, and C test fp128_conversions.c fails on power10):
* Power10 little endian, IEEE long double, --with-cpu=power10
* Power9 little endian, IEEE long double, --with-cpu=power9
Can I check this change into the master branch?
2023-01-19 Michael Meissner <meissner@linux.ibm.com>
PR target/107299
* config/rs6000/_divkc3.c (COPYSIGN): Use the correct built-in based on
whether long double is IBM or IEEE.
(INFINITY): Likewise.
(FABS): Likewise.
* config/rs6000/_mulkc3.c (COPYSIGN): Likewise.
(INFINITY): Likewise.
* config/rs6000/quad-float128.h (TF): Remove definition.
(TFtype): Define to be long double or _Float128.
(TCtype): Define to be _Complex long double or _Complex _Float128.
* libgcc2.h (TFtype): Allow machine config files to override this.
(TCtype): Likewise.
* soft-fp/quad.h (TFtype): Likewise.
---
libgcc/config/rs6000/_divkc3.c | 8 ++++++++
libgcc/config/rs6000/_mulkc3.c | 7 +++++++
libgcc/config/rs6000/quad-float128.h | 19 ++++++-------------
libgcc/libgcc2.h | 4 ++++
libgcc/soft-fp/quad.h | 2 ++
5 files changed, 27 insertions(+), 13 deletions(-)
@@ -26,9 +26,17 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
#include "soft-fp.h"
#include "quad-float128.h"
+#ifndef __LONG_DOUBLE_IEEE128__
#define COPYSIGN(x,y) __builtin_copysignf128 (x, y)
#define INFINITY __builtin_inff128 ()
#define FABS __builtin_fabsf128
+
+#else
+#define COPYSIGN(x,y) __builtin_copysignl (x, y)
+#define INFINITY __builtin_infl ()
+#define FABS __builtin_fabsl
+#endif
+
#define isnan __builtin_isnan
#define isinf __builtin_isinf
#define isfinite __builtin_isfinite
@@ -26,8 +26,15 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
#include "soft-fp.h"
#include "quad-float128.h"
+#ifndef __LONG_DOUBLE_IEEE128__
#define COPYSIGN(x,y) __builtin_copysignf128 (x, y)
#define INFINITY __builtin_inff128 ()
+
+#else
+#define COPYSIGN(x,y) __builtin_copysignl (x, y)
+#define INFINITY __builtin_infl ()
+#endif
+
#define isnan __builtin_isnan
#define isinf __builtin_isinf
@@ -27,21 +27,14 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
-/* quad.h defines the TFtype type by:
- typedef float TFtype __attribute__ ((mode (TF)));
-
- This define forces it to use KFmode (aka, ieee 128-bit floating point).
- However, when the compiler's default is changed so that long double is IEEE
- 128-bit floating point, we need to go back to using TFmode and TCmode. */
-#ifndef __LONG_DOUBLE_IEEE128__
-#define TF KF
-
-/* We also need TCtype to represent complex ieee 128-bit float for
- __mulkc3 and __divkc3. */
-typedef __complex float TCtype __attribute__ ((mode (KC)));
+/* Override the types for IEEE 128-bit scalar and complex. */
+#ifdef __LONG_DOUBLE_IEEE128__
+#define TFtype long double
+#define TCtype _Complex long double
#else
-typedef __complex float TCtype __attribute__ ((mode (TC)));
+#define TFtype _Float128
+#define TCtype _Complex _Float128
#endif
/* Force the use of the VSX instruction set. */
@@ -156,9 +156,13 @@ typedef float XFtype __attribute__ ((mode (XF)));
typedef _Complex float XCtype __attribute__ ((mode (XC)));
#endif
#if LIBGCC2_HAS_TF_MODE
+#ifndef TFtype
typedef float TFtype __attribute__ ((mode (TF)));
+#endif
+#ifndef TCtype
typedef _Complex float TCtype __attribute__ ((mode (TC)));
#endif
+#endif
typedef int cmp_return_type __attribute__((mode (__libgcc_cmp_return__)));
typedef int shift_count_type __attribute__((mode (__libgcc_shift_count__)));
@@ -65,7 +65,9 @@
#define _FP_HIGHBIT_DW_Q \
((_FP_W_TYPE) 1 << (_FP_WFRACBITS_DW_Q - 1) % _FP_W_TYPE_SIZE)
+#ifndef TFtype
typedef float TFtype __attribute__ ((mode (TF)));
+#endif
#if _FP_W_TYPE_SIZE < 64