FIX #1427, #1569: gcc 4.2.x needs -fno-toplevel-reorder

We now have various flags that need to be passed to gcc, but only if
the local gcc version supports them.  So instead of wiring this
knowledge into ghc when it is built, we now put these "extra gcc
flags" into a text file in $libdir, extra-gcc-flags, which is created
by configure.  It is also created by the configure script of a binary
distribution, so a binary dist is independent of the gcc version used
to build it.

Hopefully I got the binary-dist stuff right, but binary dists aren't
currently working so we'll need to come back and check this.

8 files changed, 79 insertions, 66 deletions

diff --git a/Makefile b/Makefile
index 981fec0d8c..192a0d5cc1 100644
--- a/Makefile
+++ b/Makefile
@@ -199,6 +199,11 @@ install ::
 endif
 endif
 
+# Install gcc-extra-opts
+install ::
+	@$(INSTALL_DIR) $(libdir)
+	$(INSTALL_DATA) $(INSTALL_OPTS) extra-gcc-opts $(libdir)
+
 install-docs ::
 	@case '${MFLAGS}' in *-[ik]*) x_on_err=0;; *-r*[ik]*) x_on_err=0;; *) x_on_err=1;; esac; \
 	for i in $(SUBDIRS); do \
@@ -262,6 +267,7 @@ BIN_DIST_TOP= distrib/Makefile \
               ANNOUNCE \
               LICENSE \
               install-sh \
+	      extra-gcc-opts.in \
               config.guess \
               config.sub   \
               aclocal.m4
diff --git a/aclocal.m4 b/aclocal.m4
index e5aed8acb6..12db959bb1 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -936,45 +936,47 @@ AC_SUBST([GhcHasReadline], [`echo $fp_cv_ghc_has_readline | sed 'y/yesno/YESNO/'
 ])# FP_GHC_HAS_READLINE
 
 
-# FP_GCC_NEEDS_NO_OMIT_LFPTR
-# --------------------------
+# FP_GCC_EXTRA_FLAGS
+# ------------------
+# Determine which extra flags we need to pass gcc when we invoke it
+# to compile .hc code.
+#
 # Some OSs (Mandrake Linux, in particular) configure GCC with
-# -momit-leaf-frame-pointer on by default. If this is the case, we need to turn
-# it off for mangling to work. The test is currently a bit crude, using only the
-# version number of gcc. Defines HAVE_GCC_MNO_OMIT_LFPTR.
-AC_DEFUN([FP_GCC_NEEDS_NO_OMIT_LFPTR],
-[AC_REQUIRE([FP_HAVE_GCC])
-AC_CACHE_CHECK([whether gcc needs -mno-omit-leaf-frame-pointer], [fp_cv_gcc_needs_no_omit_lfptr],
-[FP_COMPARE_VERSIONS([$fp_gcc_version], [-ge], [3.2],
-  [fp_cv_gcc_needs_no_omit_lfptr=yes],
-  [fp_cv_gcc_needs_no_omit_lfptr=no])])
-if test "$fp_cv_gcc_needs_no_omit_lfptr" = "yes"; then
-   AC_DEFINE([HAVE_GCC_MNO_OMIT_LFPTR], [1], [Define to 1 if gcc supports -mno-omit-leaf-frame-pointer.])
-fi])# FP_GCC_NEEDS_NO_OMIT_LFPTR
-
-# FP_GCC_HAS_NO_UNIT_AT_A_TIME
-# --------------------------
-AC_DEFUN([FP_GCC_HAS_NO_UNIT_AT_A_TIME],
+# -momit-leaf-frame-pointer on by default. If this is the case, we
+# need to turn it off for mangling to work. The test is currently a
+# bit crude, using only the version number of gcc.
+# 
+# -fwrapv is needed for gcc to emit well-behaved code in the presence of
+# integer wrap around. (Trac #952)
+#
+# -fno-unit-at-a-time or -fno-toplevel-reoder is necessary to avoid gcc
+# reordering things in the module and confusing the manger and/or splitter.
+# (eg. Trac #1427)
+#
+AC_DEFUN([FP_GCC_EXTRA_FLAGS],
 [AC_REQUIRE([FP_HAVE_GCC])
-AC_CACHE_CHECK([whether gcc has -fno-unit-at-a-time], [fp_cv_gcc_has_no_unit_at_a_time],
-[FP_COMPARE_VERSIONS([$fp_gcc_version], [-ge], [3.4],
-  [fp_cv_gcc_has_no_unit_at_a_time=yes],
-  [fp_cv_gcc_has_no_unit_at_a_time=no])])
-if test "$fp_cv_gcc_has_no_unit_at_a_time" = "yes"; then
-   AC_DEFINE([HAVE_GCC_HAS_NO_UNIT_AT_A_TIME], [1], [Define to 1 if gcc supports -fno-unit-at-a-time.])
-fi])
+AC_CACHE_CHECK([for extra options to pass gcc when compiling via C], [fp_cv_gcc_extra_opts],
+[fp_cv_gcc_extra_opts=
+ FP_COMPARE_VERSIONS([$fp_gcc_version], [-ge], [3.4],
+  [fp_cv_gcc_extra_opts="$fp_cv_gcc_extra_opts -fwrapv"],
+  [])
+ case $TargetPlatform in
+  i386-*|x86_64-*) 
+     FP_COMPARE_VERSIONS([$fp_gcc_version], [-ge], [3.2],
+      [fp_cv_gcc_extra_opts="$fp_cv_gcc_extra_opts -mno-omit-leaf-frame-pointer"],
+      [])
+    FP_COMPARE_VERSIONS([$fp_gcc_version], [-ge], [3.4],
+     [FP_COMPARE_VERSIONS([$fp_gcc_version], [-ge], [4.2],
+       [fp_cv_gcc_extra_opts="$fp_cv_gcc_extra_opts -fno-toplevel-reorder"],
+       [fp_cv_gcc_extra_opts="$fp_cv_gcc_extra_opts -fno-unit-at-a-time"]
+     )],
+     [])
+  ;;
+ esac
+])
+AC_SUBST([GccExtraViaCOpts],$fp_cv_gcc_extra_opts)
+])
 
-# FP_GCC_HAS_WRAPV
-# --------------------------
-AC_DEFUN([FP_GCC_HAS_WRAPV],
-[AC_REQUIRE([FP_HAVE_GCC])
-AC_CACHE_CHECK([whether gcc has -fwrapv], [fp_cv_gcc_has_wrapv],
-[FP_COMPARE_VERSIONS([$fp_gcc_version], [-ge], [3.4],
-  [fp_cv_gcc_has_wrapv=yes],
-  [fp_cv_gcc_has_wrapv=no])])
-if test "$fp_cv_gcc_has_wrapv" = "yes"; then
-   AC_DEFINE([HAVE_GCC_HAS_WRAPV], [1], [Define to 1 if gcc supports -fwrapv.])
-fi])
 
 # FP_SETUP_PROJECT_VERSION
 # ---------------------
diff --git a/compiler/main/DriverPipeline.hs b/compiler/main/DriverPipeline.hs
index e414f4cb3d..cf6bff18ee 100644
--- a/compiler/main/DriverPipeline.hs
+++ b/compiler/main/DriverPipeline.hs
@@ -811,6 +811,7 @@ runPhase cc_phase stop dflags basename suff input_fn get_output_fn maybe_loc
 			      (cmdline_include_paths ++ pkg_include_dirs)
 
 	let (md_c_flags, md_regd_c_flags) = machdepCCOpts dflags
+        gcc_extra_viac_flags <- getExtraViaCOpts dflags
         let pic_c_flags = picCCOpts dflags
 
         let verb = getVerbFlag dflags
@@ -877,6 +878,13 @@ runPhase cc_phase stop dflags basename suff input_fn get_output_fn maybe_loc
 		       ++ (if hcc && mangle
 		  	     then md_regd_c_flags
 		  	     else [])
+		       ++ (if hcc
+		  	     then if mangle 
+                                     then gcc_extra_viac_flags
+                                     else filter (=="-fwrapv")
+                                                gcc_extra_viac_flags
+                                -- still want -fwrapv even for unreg'd
+		  	     else [])
 		       ++ (if hcc 
 			     then more_hcc_opts
 			     else [])
@@ -886,10 +894,6 @@ runPhase cc_phase stop dflags basename suff input_fn get_output_fn maybe_loc
 		       ++ split_opt
 		       ++ include_paths
 		       ++ pkg_extra_cc_opts
-#ifdef HAVE_GCC_HAS_WRAPV
-                  -- We need consistent integer overflow (trac #952)
-               ++ ["-fwrapv"]
-#endif
 		       ))
 
 	return (next_phase, dflags, maybe_loc, output_fn)
diff --git a/compiler/main/DynFlags.hs b/compiler/main/DynFlags.hs
index 8880550fa3..1721b4c0b3 100644
--- a/compiler/main/DynFlags.hs
+++ b/compiler/main/DynFlags.hs
@@ -1515,6 +1515,18 @@ setOptHpcDir arg  = upd $ \ d -> d{hpcDir = arg}
 -----------------------------------------------------------------------------
 -- Via-C compilation stuff
 
+-- There are some options that we need to pass to gcc when compiling
+-- Haskell code via C, but are only supported by recent versions of
+-- gcc.  The configure script decides which of these options we need,
+-- and puts them in the file "extra-gcc-opts" in $topdir, which is
+-- read before each via-C compilation.  The advantage of having these
+-- in a separate file is that the file can be created at install-time
+-- depending on the available gcc version, and even re-generated  later
+-- if gcc is upgraded.
+--
+-- The options below are not dependent on the version of gcc, only the
+-- platform.
+
 machdepCCOpts :: DynFlags -> ([String], -- flags for all C compilations
 			      [String]) -- for registerised HC compilations
 machdepCCOpts dflags
@@ -1557,20 +1569,6 @@ machdepCCOpts dflags
 --                    , if "mingw32" `isSuffixOf` cTARGETPLATFORM then "-mno-cygwin" else "" 
 		      ],
 		      [ "-fno-defer-pop",
-#ifdef HAVE_GCC_MNO_OMIT_LFPTR
-			-- Some gccs are configured with
-			-- -momit-leaf-frame-pointer on by default, and it
-			-- apparently takes precedence over 
-			-- -fomit-frame-pointer, so we disable it first here.
-			"-mno-omit-leaf-frame-pointer",
-#endif
-#ifdef HAVE_GCC_HAS_NO_UNIT_AT_A_TIME
-		 	"-fno-unit-at-a-time",
-			-- unit-at-a-time doesn't do us any good, and screws
-			-- up -split-objs by moving the split markers around.
-			-- It's only turned on with -O2, but put it here just
-			-- in case someone uses -optc-O2.
-#endif
 			"-fomit-frame-pointer",
 			-- we want -fno-builtin, because when gcc inlines
 			-- built-in functions like memcpy() it tends to
@@ -1589,13 +1587,6 @@ machdepCCOpts dflags
 			-- and get in the way of -split-objs.  Another option
 			-- would be to throw them away in the mangler, but this
 			-- is easier.
-#ifdef HAVE_GCC_HAS_NO_UNIT_AT_A_TIME
-		 "-fno-unit-at-a-time",
-			-- unit-at-a-time doesn't do us any good, and screws
-			-- up -split-objs by moving the split markers around.
-			-- It's only turned on with -O2, but put it here just
-			-- in case someone uses -optc-O2.
-#endif
 		 "-fno-builtin"
 			-- calling builtins like strlen() using the FFI can
 			-- cause gcc to run out of regs, so use the external
diff --git a/compiler/main/SysTools.lhs b/compiler/main/SysTools.lhs
index 64e7b7803f..e098dd9eab 100644
--- a/compiler/main/SysTools.lhs
+++ b/compiler/main/SysTools.lhs
@@ -22,6 +22,7 @@ module SysTools (
 	copy,
         copyWithHeader,
 	normalisePath,          -- FilePath -> FilePath
+        getExtraViaCOpts,
 	
 	-- Temporary-file management
 	setTmpDir,
@@ -536,6 +537,10 @@ copyWithHeader dflags purpose maybe_header from to = do
   hPutStr h ls
   hClose h
 
+getExtraViaCOpts :: DynFlags -> IO [String]
+getExtraViaCOpts dflags = do
+  f <- readFile (topDir dflags `joinFileName` "extra-gcc-opts")
+  return (words f)
 \end{code}
 
 %************************************************************************
diff --git a/configure.ac b/configure.ac
index b35c7e7d39..8dec569392 100644
--- a/configure.ac
+++ b/configure.ac
@@ -876,9 +876,7 @@ dnl     If gcc, make sure it's at least 2.1
 dnl
 FP_HAVE_GCC
 FP_MINGW_GCC
-FP_GCC_NEEDS_NO_OMIT_LFPTR
-FP_GCC_HAS_NO_UNIT_AT_A_TIME
-FP_GCC_HAS_WRAPV
+FP_GCC_EXTRA_FLAGS
 
 dnl ** figure out how to invoke cpp directly (gcc -E is no good)
 AC_PROG_CPP
@@ -1230,6 +1228,6 @@ else
 fi
 AC_SUBST(HavePapi)
 
-AC_CONFIG_FILES([mk/config.mk ghc.spec docs/users_guide/ug-book.xml])
+AC_CONFIG_FILES([mk/config.mk ghc.spec extra-gcc-opts docs/users_guide/ug-book.xml])
 AC_CONFIG_COMMANDS([mk/stamp-h],[echo timestamp > mk/stamp-h])
 AC_OUTPUT
diff --git a/distrib/configure-bin.ac b/distrib/configure-bin.ac
index 0d01388e80..8d9ea90d27 100644
--- a/distrib/configure-bin.ac
+++ b/distrib/configure-bin.ac
@@ -148,7 +148,13 @@ FP_HAVE_GCC
 AC_PROG_CPP
 
 #
-AC_OUTPUT(Makefile-vars)
+dnl ** Check gcc version and flags we need to pass it **
+#
+FP_GCC_EXTRA_FLAGS
+
+#
+AC_CONFIG_FILES(Makefile-vars extra-gcc-opts)
+AC_OUTPUT
 
 echo "****************************************************"
 echo "Configuration done, ready to either 'make install'"
diff --git a/extra-gcc-opts.in b/extra-gcc-opts.in
new file mode 100644
index 0000000000..8c9832c835
--- /dev/null
+++ b/extra-gcc-opts.in
@@ -0,0 +1 @@
+@GccExtraViaCOpts@