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| author | Ben Gamari <bgamari.foss@gmail.com> | 2018-02-03 11:37:01 -0500 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2018-02-03 11:37:14 -0500 |
| commit | 217e4170bdce3df28a667803ce5e619553bfecdd (patch) | |
| tree | 1e548bae29aecc72ce257dc962025c1388a7a7b5 /aclocal.m4 | |
| parent | fdf518c708dc5a34ae810c5d5f3a4db812d226f0 (diff) | |
| download | haskell-217e4170bdce3df28a667803ce5e619553bfecdd.tar.gz | |
ghc-prim: Emulate C11 atomics when not available
GCC's __sync primitives apparently "usually" imply a full barrier,
meaning they can be used to emulate the more precise C11 atomics albeit
with a loss of efficiency. This restores compatibility with GCC 4.4.
This partially reverts commit 59de290928e6903337f31c1f8107ac8a98ea145d.
Test Plan: Validate on Centos
Reviewers: hvr, simonmar, trommler
Subscribers: rwbarton, thomie, erikd, carter
GHC Trac Issues: #14244
Differential Revision: https://phabricator.haskell.org/D4364
Diffstat (limited to 'aclocal.m4')
| -rw-r--r-- | aclocal.m4 | 25 |
1 files changed, 23 insertions, 2 deletions
diff --git a/aclocal.m4 b/aclocal.m4 index 5989a13ce6..2ed2c08327 100644 --- a/aclocal.m4 +++ b/aclocal.m4 @@ -1237,15 +1237,18 @@ if test -z "$CC" then AC_MSG_ERROR([gcc is required]) fi +GccLT46=NO AC_CACHE_CHECK([version of gcc], [fp_cv_gcc_version], [ # Be sure only to look at the first occurrence of the "version " string; # Some Apple compilers emit multiple messages containing this string. fp_cv_gcc_version="`$CC -v 2>&1 | sed -n -e '1,/version /s/.*version [[^0-9]]*\([[0-9.]]*\).*/\1/p'`" - FP_COMPARE_VERSIONS([$fp_cv_gcc_version], [-lt], [4.7], - [AC_MSG_ERROR([Need at least gcc version 4.7])]) + FP_COMPARE_VERSIONS([$fp_cv_gcc_version], [-lt], [4.4], + [AC_MSG_ERROR([Need at least gcc version 4.4 (4.7+ recommended)])]) + FP_COMPARE_VERSIONS([$fp_cv_gcc_version], [-lt], [4.6], GccLT46=YES) ]) AC_SUBST([GccVersion], [$fp_cv_gcc_version]) +AC_SUBST(GccLT46) ])# FP_GCC_VERSION dnl Check to see if the C compiler is clang or llvm-gcc @@ -1278,6 +1281,24 @@ AC_SUBST(GccIsClang) rm -f conftest.txt ]) +# FP_GCC_SUPPORTS__ATOMICS +# ------------------------ +# Does gcc support the __atomic_* family of builtins? +AC_DEFUN([FP_GCC_SUPPORTS__ATOMICS], +[ + AC_REQUIRE([AC_PROG_CC]) + AC_MSG_CHECKING([whether GCC supports __atomic_ builtins]) + echo 'int test(int *x) { int y; __atomic_load(&x, &y, __ATOMIC_SEQ_CST); return x; }' > conftest.c + if $CC -c conftest.c > /dev/null 2>&1; then + CONF_GCC_SUPPORTS__ATOMICS=YES + AC_MSG_RESULT([yes]) + else + CONF_GCC_SUPPORTS__ATOMICS=NO + AC_MSG_RESULT([no]) + fi + rm -f conftest.c conftest.o +]) + # FP_GCC_SUPPORTS_NO_PIE # ---------------------- # Does gcc support the -no-pie option? If so we should pass it to gcc when |