X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FcodeGen%2FCgUtils.hs;fp=compiler%2FcodeGen%2FCgUtils.hs;h=63d99a629fa4c4bec6984d56e006dd96d179e2f0;hp=4df7c77914e62f237077a30803e021bffddff014;hb=18691d440f90a3dff4ef538091c886af505e5cf5;hpb=622c3cfe2b3ebde891981544c0eea525eaa55e6f

diff --git a/compiler/codeGen/CgUtils.hs b/compiler/codeGen/CgUtils.hs
index 4df7c77..63d99a6 100644
--- a/compiler/codeGen/CgUtils.hs
+++ b/compiler/codeGen/CgUtils.hs
@@ -601,13 +601,17 @@ assignTemp e
 			    ; stmtC (CmmAssign (CmmLocal reg) e)
 			    ; return (CmmReg (CmmLocal reg)) }
 
--- | Assign the expression to a temporary register and return an
--- expression referring to this register.
+-- | If the expression is trivial and doesn't refer to a global
+-- register, return it.  Otherwise, assign the expression to a
+-- temporary register and return an expression referring to this
+-- register.
 assignTemp_ :: CmmExpr -> FCode CmmExpr
-assignTemp_ e = do
-    reg <- newTemp (cmmExprType e)
-    stmtC (CmmAssign (CmmLocal reg) e)
-    return (CmmReg (CmmLocal reg))
+assignTemp_ e
+    | isTrivialCmmExpr e && hasNoGlobalRegs e = return e
+    | otherwise = do
+        reg <- newTemp (cmmExprType e)
+        stmtC (CmmAssign (CmmLocal reg) e)
+        return (CmmReg (CmmLocal reg))
 
 newTemp :: CmmType -> FCode LocalReg
 newTemp rep = do { uniq <- newUnique; return (LocalReg uniq rep) }