Avoid generating empty llvm.used definitions.

Avoid generating empty llvm.used definitions.

LLVM 3.3rc3 complains when the llvm.used global is an empty array, so don't
define llvm.used at all when it would be empty.

Gbp-Pq: Name llvm-3.3-compat

diff --git a/compiler/llvmGen/LlvmCodeGen.hs b/compiler/llvmGen/LlvmCodeGen.hs
index 5c2e420545abad02792a2057c89206e4f68236b5..311ce0499c2ff2cc440a6ada7091646e94f7b8a3 100644 (file)
--- a/compiler/llvmGen/LlvmCodeGen.hs
+++ b/compiler/llvmGen/LlvmCodeGen.hs
@@ -112,19 +112,19 @@ cmmProcLlvmGens :: DynFlags -> BufHandle -> UniqSupply -> LlvmEnv -> [RawCmmDecl
       -> [[LlvmVar]] -- ^ info tables that need to be marked as 'used'
       -> IO ()
 
-cmmProcLlvmGens _ _ _ _ [] _ []
-  = return ()
-
 cmmProcLlvmGens dflags h _ _ [] _ ivars
-  = let ivars' = concat ivars
-        cast x = LMBitc (LMStaticPointer (pVarLift x)) i8Ptr
-        ty     = (LMArray (length ivars') i8Ptr)
-        usedArray = LMStaticArray (map cast ivars') ty
-        lmUsed = (LMGlobalVar (fsLit "llvm.used") ty Appending
-                  (Just $ fsLit "llvm.metadata") Nothing False, Just usedArray)
-    in Prt.bufLeftRender h $ {-# SCC "llvm_used_ppr" #-}
-                             withPprStyleDoc dflags (mkCodeStyle CStyle) $
-                             pprLlvmData ([lmUsed], [])
+    | null ivars' = return ()
+    | otherwise   = Prt.bufLeftRender h $
+                        {-# SCC "llvm_used_ppr" #-}
+                        withPprStyleDoc dflags (mkCodeStyle CStyle) $
+                        pprLlvmData ([lmUsed], [])
+  where
+    ivars' = concat ivars
+    cast x = LMBitc (LMStaticPointer (pVarLift x)) i8Ptr
+    ty     = (LMArray (length ivars') i8Ptr)
+    usedArray = LMStaticArray (map cast ivars') ty
+    lmUsed = (LMGlobalVar (fsLit "llvm.used") ty Appending
+              (Just $ fsLit "llvm.metadata") Nothing False, Just usedArray)
 
 cmmProcLlvmGens dflags h us env ((CmmData _ _) : cmms) count ivars
  = cmmProcLlvmGens dflags h us env cmms count ivars