X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fcmm%2FCmmOpt.hs;h=c71f188ba75513ad525d04654b9c8ae886aaf1b6;hb=dcc7b25a12eb07285a0b717b43ce62feb1f7dae1;hp=0e35cc10b93ca33582774395b33ec3011d792592;hpb=6b89acb468c0db3337b831790f96bee4d9b54bfe;p=ghc-hetmet.git

diff --git a/compiler/cmm/CmmOpt.hs b/compiler/cmm/CmmOpt.hs
index 0e35cc1..c71f188 100644
--- a/compiler/cmm/CmmOpt.hs
+++ b/compiler/cmm/CmmOpt.hs
@@ -115,12 +115,15 @@ cmmMiniInlineStmts uses (stmt@(CmmAssign (CmmLocal (LocalReg u _)) expr) : stmts
 cmmMiniInlineStmts uses (stmt:stmts)
   = stmt : cmmMiniInlineStmts uses stmts
 
-lookForInline u expr (stmt : rest)
+lookForInline u expr stmts = lookForInline' u expr regset stmts
+    where regset = foldRegsUsed extendRegSet emptyRegSet expr
+
+lookForInline' u expr regset (stmt : rest)
   | Just 1 <- lookupUFM (countUses stmt) u, ok_to_inline
   = Just (inlineStmt u expr stmt : rest)
 
   | ok_to_skip
-  = case lookForInline u expr rest of
+  = case lookForInline' u expr regset rest of
            Nothing    -> Nothing
            Just stmts -> Just (stmt:stmts)
 
@@ -137,12 +140,18 @@ lookForInline u expr (stmt : rest)
 		     CmmCall{} -> hasNoGlobalRegs expr
 		     _ -> True
 
-   -- We can skip over assignments to other tempoararies, because we
-   -- know that expressions aren't side-effecting and temporaries are
-   -- single-assignment.
+   -- Expressions aren't side-effecting.  Temporaries may or may not
+   -- be single-assignment depending on the source (the old code
+   -- generator creates single-assignment code, but hand-written Cmm
+   -- and Cmm from the new code generator is not single-assignment.)
+   -- So we do an extra check to make sure that the register being
+   -- changed is not one we were relying on.  I don't know how much of a
+   -- performance hit this is (we have to create a regset for every
+   -- instruction.) -- EZY
     ok_to_skip = case stmt of
                  CmmNop -> True
-                 CmmAssign (CmmLocal (LocalReg u' _)) rhs | u' /= u -> True
+                 CmmComment{} -> True
+                 CmmAssign (CmmLocal r@(LocalReg u' _)) rhs | u' /= u && not (r `elemRegSet` regset) -> True
                  CmmAssign g@(CmmGlobal _) rhs -> not (g `regUsedIn` expr)
                  _other -> False
 
@@ -306,9 +315,18 @@ cmmMachOpFold op [x@(CmmLit _), y]
 -- PicBaseReg from the corresponding label (or label difference).
 --
 cmmMachOpFold mop1 [CmmMachOp mop2 [arg1,arg2], arg3]
-   | mop1 == mop2 && isAssociativeMachOp mop1
+   | mop2 `associates_with` mop1
      && not (isLit arg1) && not (isPicReg arg1)
-   = cmmMachOpFold mop1 [arg1, cmmMachOpFold mop2 [arg2,arg3]]
+   = cmmMachOpFold mop2 [arg1, cmmMachOpFold mop1 [arg2,arg3]]
+   where
+     MO_Add{} `associates_with` MO_Sub{} = True
+     mop1 `associates_with` mop2 =
+        mop1 == mop2 && isAssociativeMachOp mop1
+
+-- special case: (a - b) + c  ==>  a + (c - b)
+cmmMachOpFold mop1@(MO_Add{}) [CmmMachOp mop2@(MO_Sub{}) [arg1,arg2], arg3]
+   | not (isLit arg1) && not (isPicReg arg1)
+   = cmmMachOpFold mop1 [arg1, cmmMachOpFold mop2 [arg3,arg2]]
 
 -- Make a RegOff if we can
 cmmMachOpFold (MO_Add _) [CmmReg reg, CmmLit (CmmInt n rep)]