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| author | Marius Hillenbrand <mhillen@linux.ibm.com> | 2020-12-04 10:38:58 +0100 |
|---|---|---|
| committer | Marius Hillenbrand <mhillen@linux.ibm.com> | 2020-12-17 11:47:23 +0100 |
| commit | 33f925094d02ce40872d494d384d4494a4313779 (patch) | |
| tree | 38dbb5b156c90f3c7b9ec9eb5ba894f3cc8a8329 /gcc | |
| parent | 2f49508599f548f4b2e5f2c876be7247a1c5f8ff (diff) | |
| download | gcc-33f925094d02ce40872d494d384d4494a4313779.zip gcc-33f925094d02ce40872d494d384d4494a4313779.tar.gz gcc-33f925094d02ce40872d494d384d4494a4313779.tar.bz2 | |
IBM Z: Detect libc's float_t behavior on cross compiles
When cross-compiling GCC with target libc headers available and
configure option --enable-s390-excess-float-precision has been omitted,
identify whether they clamp float_t to double or respect
__FLT_EVAL_METHOD__ via a compile test that coerces the build-system
compiler to use the target headers. Then derive the setting from that.
gcc/ChangeLog:
2020-12-16 Marius Hillenbrand <mhillen@linux.ibm.com>
* configure.ac: Change --enable-s390-excess-float-precision
default behavior for cross compiles with target headers.
* configure: Regenerate.
* doc/install.texi: Adjust documentation.
Diffstat (limited to 'gcc')
| -rwxr-xr-x | gcc/configure | 67 | ||||
| -rw-r--r-- | gcc/configure.ac | 52 | ||||
| -rw-r--r-- | gcc/doc/install.texi | 7 |
3 files changed, 85 insertions, 41 deletions
diff --git a/gcc/configure b/gcc/configure index fe649b2..fbe9208 100755 --- a/gcc/configure +++ b/gcc/configure @@ -31855,9 +31855,9 @@ $as_echo "$ld_pushpopstate_support" >&6; } # gcc describes its behavior via the macro __FLT_EVAL_METHOD__ and glibc derives # float_t from that, this behavior can be configured with # --enable-s390-excess-float-precision. When given as enabled, that flag selects -# the old model. When omitted, native builds will derive the flag from the -# behavior of glibc. When glibc clamps float_t to double, gcc follows the old -# model. In any other case, it defaults to the new model. +# the old model. When omitted, native builds and cross compiles that have target +# libc headers will detect whether libc clamps float_t to double and in that +# case maintain the old model. Otherwise, they will default to the new model. # Check whether --enable-s390-excess-float-precision was given. if test "${enable_s390_excess_float_precision+set}" = set; then : enableval=$enable_s390_excess_float_precision; @@ -31868,42 +31868,63 @@ fi case $target in s390*-linux*) - if test "$target" = "$host" -a "$host" = "$build" -a \ - x"$enable_s390_excess_float_precision" = xauto; then - { $as_echo "$as_me:${as_lineno-$LINENO}: checking for glibc clamping float_t to double" >&5 + if test x"$enable_s390_excess_float_precision" = xauto; then + # Can we autodetect the behavior of the target libc? + if test "$target" = "$host" -a "$host" = "$build"; then + enable_s390_excess_float_precision=autodetect + elif test "x$with_headers" != xno; then + # cross build. are target headers available? + # carefully coerce the build-system compiler to use target headers + saved_CXXFLAGS="$CXXFLAGS" + CROSS_TEST_CXXFLAGS="-nostdinc ${XGCC_FLAGS_FOR_TARGET//-B/-idirafter/}" + CXXFLAGS="$CROSS_TEST_CXXFLAGS" + cat confdefs.h - <<_ACEOF >conftest.$ac_ext +/* end confdefs.h. */ + +#include <math.h> + +_ACEOF +if ac_fn_cxx_try_compile "$LINENO"; then : + enable_s390_excess_float_precision=autodetect +fi +rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext + CXXFLAGS="$saved_CXXFLAGS" + fi + + if test x"$enable_s390_excess_float_precision" = xautodetect; then + saved_CXXFLAGS="$CXXFLAGS" + if ! test "$target" = "$host" -a "$host" = "$build"; then + CXXFLAGS="$CROSS_TEST_CXXFLAGS" + unset CROSS_TEST_CXXFLAGS + fi + { $as_echo "$as_me:${as_lineno-$LINENO}: checking for glibc clamping float_t to double" >&5 $as_echo_n "checking for glibc clamping float_t to double... " >&6; } if ${gcc_cv_float_t_clamped_to_double+:} false; then : $as_echo_n "(cached) " >&6 else - if test "$cross_compiling" = yes; then : - { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5 -$as_echo "$as_me: error: in \`$ac_pwd':" >&2;} -as_fn_error $? "cannot run test program while cross compiling -See \`config.log' for more details" "$LINENO" 5; } -else - cat confdefs.h - <<_ACEOF >conftest.$ac_ext + + cat confdefs.h - <<_ACEOF >conftest.$ac_ext /* end confdefs.h. */ #define __FLT_EVAL_METHOD__ 0 #include <math.h> -int main() { - return !(sizeof(float_t) == sizeof(double)); -} +int dummy[sizeof(float_t) == sizeof(double) ? 1 : -1]; + _ACEOF -if ac_fn_cxx_try_run "$LINENO"; then : +if ac_fn_cxx_try_compile "$LINENO"; then : gcc_cv_float_t_clamped_to_double=yes else gcc_cv_float_t_clamped_to_double=no fi -rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \ - conftest.$ac_objext conftest.beam conftest.$ac_ext -fi - +rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext fi { $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_float_t_clamped_to_double" >&5 $as_echo "$gcc_cv_float_t_clamped_to_double" >&6; } - if test x"$gcc_cv_float_t_clamped_to_double" = xyes; then - enable_s390_excess_float_precision=yes + CXXFLAGS="$saved_CXXFLAGS" + enable_s390_excess_float_precision="$gcc_cv_float_t_clamped_to_double" + else + # no way to detect behavior of target libc, default to new model + enable_s390_excess_float_precision=no fi fi diff --git a/gcc/configure.ac b/gcc/configure.ac index 3755722..89b9981 100644 --- a/gcc/configure.ac +++ b/gcc/configure.ac @@ -7375,9 +7375,9 @@ AC_MSG_RESULT($ld_pushpopstate_support) # gcc describes its behavior via the macro __FLT_EVAL_METHOD__ and glibc derives # float_t from that, this behavior can be configured with # --enable-s390-excess-float-precision. When given as enabled, that flag selects -# the old model. When omitted, native builds will derive the flag from the -# behavior of glibc. When glibc clamps float_t to double, gcc follows the old -# model. In any other case, it defaults to the new model. +# the old model. When omitted, native builds and cross compiles that have target +# libc headers will detect whether libc clamps float_t to double and in that +# case maintain the old model. Otherwise, they will default to the new model. AC_ARG_ENABLE(s390-excess-float-precision, [AS_HELP_STRING([--enable-s390-excess-float-precision], [on s390 targets, evaluate float with double precision @@ -7386,20 +7386,42 @@ AC_ARG_ENABLE(s390-excess-float-precision, case $target in s390*-linux*) - if test "$target" = "$host" -a "$host" = "$build" -a \ - x"$enable_s390_excess_float_precision" = xauto; then - AC_CACHE_CHECK([for glibc clamping float_t to double], - gcc_cv_float_t_clamped_to_double, - [AC_RUN_IFELSE([AC_LANG_SOURCE([ + if test x"$enable_s390_excess_float_precision" = xauto; then + # Can we autodetect the behavior of the target libc? + if test "$target" = "$host" -a "$host" = "$build"; then + enable_s390_excess_float_precision=autodetect + elif test "x$with_headers" != xno; then + # cross build. are target headers available? + # carefully coerce the build-system compiler to use target headers + saved_CXXFLAGS="$CXXFLAGS" + CROSS_TEST_CXXFLAGS="-nostdinc ${XGCC_FLAGS_FOR_TARGET//-B/-idirafter/}" + CXXFLAGS="$CROSS_TEST_CXXFLAGS" + AC_COMPILE_IFELSE([AC_LANG_SOURCE([[ +#include <math.h> +]])], [enable_s390_excess_float_precision=autodetect], []) + CXXFLAGS="$saved_CXXFLAGS" + fi + + if test x"$enable_s390_excess_float_precision" = xautodetect; then + saved_CXXFLAGS="$CXXFLAGS" + if ! test "$target" = "$host" -a "$host" = "$build"; then + CXXFLAGS="$CROSS_TEST_CXXFLAGS" + unset CROSS_TEST_CXXFLAGS + fi + AC_CACHE_CHECK([for glibc clamping float_t to double], + gcc_cv_float_t_clamped_to_double, [ + AC_COMPILE_IFELSE([AC_LANG_SOURCE([[ #define __FLT_EVAL_METHOD__ 0 #include <math.h> -int main() { - return !(sizeof(float_t) == sizeof(double)); -}])], - [gcc_cv_float_t_clamped_to_double=yes], - [gcc_cv_float_t_clamped_to_double=no])]) - if test x"$gcc_cv_float_t_clamped_to_double" = xyes; then - enable_s390_excess_float_precision=yes +int dummy[sizeof(float_t) == sizeof(double) ? 1 : -1]; +]])], + [gcc_cv_float_t_clamped_to_double=yes], + [gcc_cv_float_t_clamped_to_double=no])]) + CXXFLAGS="$saved_CXXFLAGS" + enable_s390_excess_float_precision="$gcc_cv_float_t_clamped_to_double" + else + # no way to detect behavior of target libc, default to new model + enable_s390_excess_float_precision=no fi fi diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi index a38ca3e..e30d2fc 100644 --- a/gcc/doc/install.texi +++ b/gcc/doc/install.texi @@ -2277,9 +2277,10 @@ On s390(x) targets, enable treatment of float expressions with double precision when in standards-compliant mode (e.g., when @code{--std=c99} or @code{-fexcess-precision=standard} are given). -For a native build, the option's default is derived from glibc's behavior. When -glibc clamps float_t to double, gcc follows and enables the option. In all other -cases, it defaults to off. +For a native build and cross compiles that have target headers, the option's +default is derived from glibc's behavior. When glibc clamps float_t to double, +GCC follows and enables the option. For other cross compiles, the default is +disabled. @end table @subheading Cross-Compiler-Specific Options |