diff options
Diffstat (limited to 'gcc/configure.ac')
| -rw-r--r-- | gcc/configure.ac | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/gcc/configure.ac b/gcc/configure.ac index b410428b4fc..24679a540c1 100644 --- a/gcc/configure.ac +++ b/gcc/configure.ac @@ -7318,6 +7318,51 @@ if test x"$ld_pushpopstate_support" = xyes; then fi AC_MSG_RESULT($ld_pushpopstate_support) +# On s390, float_t has historically been statically defined as double for no +# good reason. To comply with the C standard in the light of this definition, +# gcc has evaluated float expressions in double precision when in +# standards-compatible mode or when given -fexcess-precision=standard. To enable +# a smooth transition towards the new model used by most architectures, where +# 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. +AC_ARG_ENABLE(s390-excess-float-precision, + [AS_HELP_STRING([--enable-s390-excess-float-precision], + [on s390 targets, evaluate float with double precision + when in standards-conforming mode])], + [],[enable_s390_excess_float_precision=auto]) + +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([ +#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"$gcc_cv_float_t_clamped_to_double" = xyes; then + enable_s390_excess_float_precision=yes + fi + fi + + GCC_TARGET_TEMPLATE(ENABLE_S390_EXCESS_FLOAT_PRECISION) + if test x"$enable_s390_excess_float_precision" = xyes; then + AC_DEFINE(ENABLE_S390_EXCESS_FLOAT_PRECISION, 1, +[Define to enable evaluating float expressions with double precision in +standards-compatible mode on s390 targets.]) + fi + ;; +esac + # Configure the subdirectories # AC_CONFIG_SUBDIRS($subdirs) |