X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FnativeGen%2FAsmCodeGen.lhs;h=615cc0c7bade96d485a90b0b021978ecc52b69dd;hb=2662dbc5b2c30fc11ccb99e7f9b2dba794d680ba;hp=b7e4797720cb4ed2ae4c1972a0dd37fbdde06f49;hpb=1e50fd4185479a62e02d987bdfcb1c62712859ca;p=ghc-hetmet.git

diff --git a/compiler/nativeGen/AsmCodeGen.lhs b/compiler/nativeGen/AsmCodeGen.lhs
index b7e4797..615cc0c 100644
--- a/compiler/nativeGen/AsmCodeGen.lhs
+++ b/compiler/nativeGen/AsmCodeGen.lhs
@@ -72,6 +72,7 @@ import Reg
 import RegClass
 import NCGMonad
 
+import BlockId
 import Cmm
 import CmmOpt		( cmmMiniInline, cmmMachOpFold )
 import PprCmm
@@ -236,19 +237,19 @@ cmmNativeGens dflags h us (cmm : cmms) impAcc profAcc count
 	Pretty.bufLeftRender h
 		$ {-# SCC "pprNativeCode" #-} Pretty.vcat $ map pprNatCmmTop native
 
-	let lsPprNative =
+           -- carefully evaluate this strictly.  Binding it with 'let'
+           -- and then using 'seq' doesn't work, because the let
+           -- apparently gets inlined first.
+	lsPprNative <- return $!
 		if  dopt Opt_D_dump_asm       dflags
 	         || dopt Opt_D_dump_asm_stats dflags
 			then native
 			else []
 
-	let count'	= count + 1;
-
+	count' <- return $! count + 1;
 
 	-- force evaulation all this stuff to avoid space leaks
 	seqString (showSDoc $ vcat $ map ppr imports) `seq` return ()
-	lsPprNative 	`seq` return ()
-	count'		`seq` return ()
 
 	cmmNativeGens dflags h us' cmms
 			(imports : impAcc)
@@ -630,10 +631,17 @@ build_mapping (CmmProc info lbl params (ListGraph (head:blocks)))
   where
     -- find all the blocks that just consist of a jump that can be
     -- shorted.
-    (shortcut_blocks, others) = partitionWith split blocks
-    split (BasicBlock id [insn]) | Just dest <- canShortcut insn 
-                                 = Left (id,dest)
-    split other = Right other
+    -- Don't completely eliminate loops here -- that can leave a dangling jump!
+    (_, shortcut_blocks, others) = foldl split (emptyBlockSet, [], []) blocks
+    split (s, shortcut_blocks, others) b@(BasicBlock id [insn])
+        | Just (DestBlockId dest) <- canShortcut insn,
+          (elemBlockSet dest s) || dest == id -- loop checks
+        = (s, shortcut_blocks, b : others)
+    split (s, shortcut_blocks, others) (BasicBlock id [insn])
+        | Just dest <- canShortcut insn
+        = (extendBlockSet s id, (id,dest) : shortcut_blocks, others)
+    split (s, shortcut_blocks, others) other = (s, shortcut_blocks, other : others)
+
 
     -- build a mapping from BlockId to JumpDest for shorting branches
     mapping = foldl add emptyUFM shortcut_blocks