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From: Michael Meissner <meissner@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc(refs/users/meissner/heads/work107)] Update ChangeLog.meissner Date: Mon, 23 Jan 2023 21:17:23 +0000 (GMT) [thread overview] Message-ID: <20230123211723.690223858C83@sourceware.org> (raw) https://gcc.gnu.org/g:361a72abdd82b9038dd30243f052edbddf9ffd2f commit 361a72abdd82b9038dd30243f052edbddf9ffd2f Author: Michael Meissner <meissner@linux.ibm.com> Date: Fri Jan 20 15:34:11 2023 -0500 Update ChangeLog.meissner Diff: --- gcc/ChangeLog.meissner | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) diff --git a/gcc/ChangeLog.meissner b/gcc/ChangeLog.meissner index fda09a48c25..188ac07d434 100644 --- a/gcc/ChangeLog.meissner +++ b/gcc/ChangeLog.meissner @@ -1,3 +1,72 @@ +==================== work107, patch #1 ==================== + +PR target/107299: Fix build issue when long double is IEEE 128-bit + +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? + +2023-01-20 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. + +==================== work107, branch head ==================== + 2023-01-20 Michael Meissner <meissner@linux.ibm.com> Clone branch
next reply other threads:[~2023-01-23 21:17 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-01-23 21:17 Michael Meissner [this message] -- strict thread matches above, loose matches on Subject: below -- 2023-01-25 4:42 Michael Meissner 2023-01-25 3:29 Michael Meissner 2023-01-25 3:00 Michael Meissner 2023-01-23 21:19 Michael Meissner 2023-01-23 21:17 Michael Meissner 2023-01-20 21:02 Michael Meissner 2023-01-20 20:34 Michael Meissner
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