Set AIX specific CFLAGS flags

First of all, we need to use -mminimal-toc on IBM AIX

AIX's XCOFF is limited to 16k entries in its TOC for 32bit compilation,
which quickly overflows with GHC's code generation.

Otoh, the Parser.hs module contains more entries than fit into a
minimal-toc, so we need to switch back to `-mfull-toc` for that single
module again.

Then, we also need to set the `THREAD_SAFE` CPP #define in order to
unlock the thread-safe `errno` which is essential for the threaded
runtime.

Depends on D1501

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie, erikd

Differential Revision: https://phabricator.haskell.org/D1502

1 files changed, 14 insertions, 0 deletions

diff --git a/aclocal.m4 b/aclocal.m4
index e816e09b54..4bd8198beb 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -587,6 +587,20 @@ AC_DEFUN([FPTOOLS_SET_C_LD_FLAGS],
         $3="$$3 -fuse-ld=gold -Wl,-z,noexecstack"
         $4="$$4 -z noexecstack"
         ;;
+
+    powerpc-ibm-aix*)
+        # On IBM AIX, we need to workaround XCOFF's limitations. Specifically,
+        # there's a TOC which only supports at most 16k entries (see
+        # http://www.ibm.com/developerworks/rational/library/overview-toc-aix/
+        # for more details), and by using `-mminimal-toc` we use up only one TOC
+        # entry per translation unit, at the cost of an additional pointer
+        # indirection. However, see note in `compiler/ghc.mk` about `Parser.hs`.
+        # Finally, we need `-D_THREAD_SAFE` to unlock a thread-local `errno`.
+        $2="$$2 -mminimal-toc -D_THREAD_SAFE"
+        $3="$$3 -mminimal-toc -D_THREAD_SAFE"
+        $5="$$5 -D_THREAD_SAFE"
+        ;;
+
     esac
 
     # If gcc knows about the stack protector, turn it off.