diff options
Diffstat (limited to 'config/c-compiler.m4')
| -rw-r--r-- | config/c-compiler.m4 | 48 |
1 files changed, 40 insertions, 8 deletions
diff --git a/config/c-compiler.m4 b/config/c-compiler.m4 index 8d9844abc6d..4a512cedd46 100644 --- a/config/c-compiler.m4 +++ b/config/c-compiler.m4 @@ -108,29 +108,61 @@ AC_DEFUN([PGAC_TYPE_128BIT_INT], [AC_CACHE_CHECK([for __int128], [pgac_cv__128bit_int], [AC_LINK_IFELSE([AC_LANG_PROGRAM([ /* + * We don't actually run this test, just link it to verify that any support + * functions needed for __int128 are present. + * * These are globals to discourage the compiler from folding all the * arithmetic tests down to compile-time constants. We do not have - * convenient support for 64bit literals at this point... + * convenient support for 128bit literals at this point... */ __int128 a = 48828125; -__int128 b = 97656255; +__int128 b = 97656250; ],[ __int128 c,d; a = (a << 12) + 1; /* 200000000001 */ b = (b << 12) + 5; /* 400000000005 */ -/* use the most relevant arithmetic ops */ +/* try the most relevant arithmetic ops */ c = a * b; d = (c + b) / b; -/* return different values, to prevent optimizations */ +/* must use the results, else compiler may optimize arithmetic away */ if (d != a+1) - return 0; -return 1; + return 1; ])], [pgac_cv__128bit_int=yes], [pgac_cv__128bit_int=no])]) if test x"$pgac_cv__128bit_int" = xyes ; then - AC_DEFINE(PG_INT128_TYPE, __int128, [Define to the name of a signed 128-bit integer type.]) - AC_CHECK_ALIGNOF(PG_INT128_TYPE) + # Use of non-default alignment with __int128 tickles bugs in some compilers. + # If not cross-compiling, we can test for bugs and disable use of __int128 + # with buggy compilers. If cross-compiling, hope for the best. + # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83925 + AC_CACHE_CHECK([for __int128 alignment bug], [pgac_cv__128bit_int_bug], + [AC_RUN_IFELSE([AC_LANG_PROGRAM([ +/* This must match the corresponding code in c.h: */ +#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__) +#define pg_attribute_aligned(a) __attribute__((aligned(a))) +#endif +typedef __int128 int128a +#if defined(pg_attribute_aligned) +pg_attribute_aligned(8) +#endif +; +int128a holder; +void pass_by_val(void *buffer, int128a par) { holder = par; } +],[ +long int i64 = 97656225L << 12; +int128a q; +pass_by_val(main, (int128a) i64); +q = (int128a) i64; +if (q != holder) + return 1; +])], + [pgac_cv__128bit_int_bug=ok], + [pgac_cv__128bit_int_bug=broken], + [pgac_cv__128bit_int_bug="assuming ok"])]) + if test x"$pgac_cv__128bit_int_bug" != xbroken ; then + AC_DEFINE(PG_INT128_TYPE, __int128, [Define to the name of a signed 128-bit integer type.]) + AC_CHECK_ALIGNOF(PG_INT128_TYPE) + fi fi])# PGAC_TYPE_128BIT_INT |