Only test for bug #9439 when llvm is installed

Reviewers: bgamari, austin

Reviewed By: austin

Subscribers: thomie, carter

Differential Revision: https://phabricator.haskell.org/D500

GHC Trac Issues: #9807

configure.ac

@@ -187,56 +187,6 @@ AC_SUBST([WithGhc])
 dnl ** Without optimization some INLINE trickery fails for GHCi
 SRC_CC_OPTS="-O"
 
-dnl ** Bug 9439: Some GHC 7.8 releases had broken LLVM code generator.
-dnl Unfortunately we don't know whether the user is going to request a
-dnl build with the LLVM backend as this is only given in build.mk.
-dnl
-dnl Instead, we try to do as much work as possible here, checking
-dnl whether -fllvm is the stage 0 compiler's default. If so we
-dnl fail. If not, we check whether -fllvm is affected explicitly and
-dnl if so set a flag. The build system will later check this flag
-dnl after the desired build flags are known.
-AC_MSG_CHECKING(whether bootstrap compiler is affected by bug 9439)
-echo "main = putStrLn \"%function\"" > conftestghc.hs
-
-# Check whether LLVM backend is default for this platform
-"${WithGhc}" conftestghc.hs 2>&1 >/dev/null
-res=`./conftestghc`
-if test "x$res" == "x%object"
-then
-    AC_MSG_RESULT(yes)
-    echo "Buggy bootstrap compiler"
-    echo ""
-    echo "The stage 0 compiler $WithGhc is affected by GHC Bug \#9439"
-    echo "and therefore will miscompile the LLVM backend if -fllvm is"
-    echo "used."
-    echo
-    echo "Please use another bootstrap compiler"
-    exit 1
-fi
-
-# -fllvm is not the default, but set a flag so the Makefile can check
-# -for it in the build flags later on
-"${WithGhc}" -fforce-recomp -fllvm conftestghc.hs 2>&1 >/dev/null
-if test $? == 0
-then
-    res=`./conftestghc`
-    if test "x$res" == "x%object"
-    then
-        AC_MSG_RESULT(yes)
-        GHC_LLVM_AFFECTED_BY_9439=1
-    elif test "x$res" == "x%function"
-    then
-        AC_MSG_RESULT(no)
-        GHC_LLVM_AFFECTED_BY_9439=0
-    else
-        AC_MSG_WARN(unexpected output $res)
-    fi
-else
-    AC_MSG_RESULT(failed to compile, assuming no)
-fi
-AC_SUBST([GHC_LLVM_AFFECTED_BY_9439])
-
 dnl--------------------------------------------------------------------
 dnl * Choose host(/target/build) platform
 dnl--------------------------------------------------------------------
@@ -593,6 +543,59 @@ dnl --------------------------------------------------------------
 dnl * General configuration checks
 dnl --------------------------------------------------------------
 
+dnl ** Bug 9439: Some GHC 7.8 releases had broken LLVM code generator.
+dnl Unfortunately we don't know whether the user is going to request a
+dnl build with the LLVM backend as this is only given in build.mk.
+dnl
+dnl Instead, we try to do as much work as possible here, checking
+dnl whether -fllvm is the stage 0 compiler's default. If so we
+dnl fail. If not, we check whether -fllvm is affected explicitly and
+dnl if so set a flag. The build system will later check this flag
+dnl after the desired build flags are known.
+if test -n "$LlcCmd" && test -n "$OptCmd"
+then
+    AC_MSG_CHECKING(whether bootstrap compiler is affected by bug 9439)
+    echo "main = putStrLn \"%function\"" > conftestghc.hs
+
+    # Check whether LLVM backend is default for this platform
+    "${WithGhc}" conftestghc.hs 2>&1 >/dev/null
+    res=`./conftestghc`
+    if test "x$res" == "x%object"
+    then
+        AC_MSG_RESULT(yes)
+        echo "Buggy bootstrap compiler"
+        echo ""
+        echo "The stage 0 compiler $WithGhc is affected by GHC Bug \#9439"
+        echo "and therefore will miscompile the LLVM backend if -fllvm is"
+        echo "used."
+        echo
+        echo "Please use another bootstrap compiler"
+        exit 1
+    fi
+
+    # -fllvm is not the default, but set a flag so the Makefile can check
+    # -for it in the build flags later on
+    "${WithGhc}" -fforce-recomp -fllvm conftestghc.hs 2>&1 >/dev/null
+    if test $? == 0
+    then
+        res=`./conftestghc`
+        if test "x$res" == "x%object"
+        then
+            AC_MSG_RESULT(yes)
+            GHC_LLVM_AFFECTED_BY_9439=1
+        elif test "x$res" == "x%function"
+        then
+            AC_MSG_RESULT(no)
+            GHC_LLVM_AFFECTED_BY_9439=0
+        else
+            AC_MSG_WARN(unexpected output $res)
+        fi
+    else
+        AC_MSG_RESULT(failed to compile, assuming no)
+    fi
+fi
+AC_SUBST([GHC_LLVM_AFFECTED_BY_9439])
+
 dnl ** Can the unix package be built?
 dnl --------------------------------------------------------------