X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FnativeGen%2FAsmCodeGen.lhs;h=ff3063c98dfff71e1e480ae9c2068e69e40c4b36;hb=46b28f7bfdd535e9fe5217a1151bedfb2cc15472;hp=109054fb9f621b1e1fc033c1e5d949cb6f975f85;hpb=e4c8d2b11b4be71885532cb14434511b6c47866c;p=ghc-hetmet.git

diff --git a/compiler/nativeGen/AsmCodeGen.lhs b/compiler/nativeGen/AsmCodeGen.lhs
index 109054f..ff3063c 100644
--- a/compiler/nativeGen/AsmCodeGen.lhs
+++ b/compiler/nativeGen/AsmCodeGen.lhs
@@ -17,7 +17,7 @@ import MachRegs
 import MachCodeGen
 import PprMach
 import RegisterAlloc
-import RegAllocInfo	( jumpDests )
+import RegAllocInfo
 import NCGMonad
 import PositionIndependentCode
 
@@ -25,20 +25,17 @@ import Cmm
 import CmmOpt		( cmmMiniInline, cmmMachOpFold )
 import PprCmm		( pprStmt, pprCmms )
 import MachOp
-import CLabel           ( CLabel, mkSplitMarkerLabel, mkAsmTempLabel )
-#if powerpc_TARGET_ARCH
-import CLabel           ( mkRtsCodeLabel )
-#endif
+import CLabel
 
 import UniqFM
 import Unique		( Unique, getUnique )
 import UniqSupply
 import FastTypes
 import List		( groupBy, sortBy )
-import CLabel           ( pprCLabel )
 import ErrUtils		( dumpIfSet_dyn )
-import DynFlags		( DynFlags, DynFlag(..), dopt )
+import DynFlags
 import StaticFlags	( opt_Static, opt_PIC )
+import Util
 import Config           ( cProjectVersion )
 
 import Digraph
@@ -212,8 +209,10 @@ cmmNativeGen dflags cmm
 	genMachCode cmm              `thenUs` \ (pre_regalloc, lastMinuteImports) ->
      {-# SCC "regAlloc"         #-}
 	mapUs regAlloc pre_regalloc `thenUs`   \ with_regs ->
+     {-# SCC "shortcutBranches"   #-}
+        shortcutBranches dflags with_regs `bind` \ shorted -> 
      {-# SCC "sequenceBlocks"   #-}
-	map sequenceTop with_regs    `bind`   \ sequenced ->
+	map sequenceTop shorted        `bind`   \ sequenced ->
      {-# SCC "x86fp_kludge"     #-}
 	map x86fp_kludge sequenced   `bind`   \ final_mach_code ->
      {-# SCC "vcat"             #-}
@@ -330,6 +329,48 @@ makeFarBranches = id
 #endif
 
 -- -----------------------------------------------------------------------------
+-- Shortcut branches
+
+shortcutBranches :: DynFlags -> [NatCmmTop] -> [NatCmmTop]
+shortcutBranches dflags tops
+  | optLevel dflags < 1 = tops    -- only with -O or higher
+  | otherwise           = map (apply_mapping mapping) tops'
+  where
+    (tops', mappings) = mapAndUnzip build_mapping tops
+    mapping = foldr plusUFM emptyUFM mappings
+
+build_mapping top@(CmmData _ _) = (top, emptyUFM)
+build_mapping (CmmProc info lbl params [])
+  = (CmmProc info lbl params [], emptyUFM)
+build_mapping (CmmProc info lbl params (head:blocks))
+  = (CmmProc info lbl params (head:others), mapping)
+        -- drop the shorted blocks, but don't ever drop the first one,
+        -- because it is pointed to by a global label.
+  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
+
+    -- build a mapping from BlockId to JumpDest for shorting branches
+    mapping = foldl add emptyUFM shortcut_blocks
+    add ufm (id,dest) = addToUFM ufm id dest
+    
+apply_mapping ufm (CmmData sec statics) 
+  = CmmData sec (map (shortcutStatic (lookupUFM ufm)) statics)
+  -- we need to get the jump tables, so apply the mapping to the entries
+  -- of a CmmData too.
+apply_mapping ufm (CmmProc info lbl params blocks)
+  = CmmProc info lbl params (map short_bb blocks)
+  where
+    short_bb (BasicBlock id insns) = BasicBlock id $! map short_insn insns
+    short_insn i = shortcutJump (lookupUFM ufm) i
+                 -- shortcutJump should apply the mapping repeatedly,
+                 -- just in case we can short multiple branches.
+
+-- -----------------------------------------------------------------------------
 -- Instruction selection
 
 -- Native code instruction selection for a chunk of stix code.  For