Refactoring: explicitly mark whether we have an info table in RawCmm

I introduced this to support explicitly recording the info table label
in RawCmm for another patch I am working on, but it turned out to lead
to significant simplification in those parts of the compiler that
consume RawCmm.

Now, instead of lots of tests for null [CmmStatic] we have a simple
test of a Maybe, and have reduced the number of guys that need to know
how to convert entry->info labels by a TON. There are only 3 callers
of that function now!

6 files changed, 56 insertions, 49 deletions

diff --git a/compiler/nativeGen/AsmCodeGen.lhs b/compiler/nativeGen/AsmCodeGen.lhs
index bfeaf9e8e3..83082eaab8 100644
--- a/compiler/nativeGen/AsmCodeGen.lhs
+++ b/compiler/nativeGen/AsmCodeGen.lhs
@@ -267,7 +267,7 @@ nativeCodeGen' dflags ncgImpl h us cmms
 		| dopt Opt_SplitObjs dflags = split_marker : tops
 		| otherwise		    = tops
 
-	split_marker = CmmProc [] mkSplitMarkerLabel (ListGraph [])
+	split_marker = CmmProc Nothing mkSplitMarkerLabel (ListGraph [])
 
 
 -- | Do native code generation on all these cmms.
diff --git a/compiler/nativeGen/Instruction.hs b/compiler/nativeGen/Instruction.hs
index 5c85101e8e..7bcaa2b2a9 100644
--- a/compiler/nativeGen/Instruction.hs
+++ b/compiler/nativeGen/Instruction.hs
@@ -38,13 +38,13 @@ noUsage  = RU [] []
 type NatCmm instr
 	= GenCmm
 		CmmStatics
-		[CmmStatic]
+		(Maybe CmmStatics)
 		(ListGraph instr)
 
 type NatCmmTop statics instr
 	= GenCmmTop
 		statics
-		[CmmStatic]
+		(Maybe CmmStatics)
 		(ListGraph instr)
 
 
diff --git a/compiler/nativeGen/PPC/Ppr.hs b/compiler/nativeGen/PPC/Ppr.hs
index 7d85b4c66b..3209e9981c 100644
--- a/compiler/nativeGen/PPC/Ppr.hs
+++ b/compiler/nativeGen/PPC/Ppr.hs
@@ -54,19 +54,23 @@ pprNatCmmTop (CmmData section dats) =
   pprSectionHeader section $$ pprDatas dats
 
  -- special case for split markers:
-pprNatCmmTop (CmmProc [] lbl (ListGraph [])) = pprLabel lbl
+pprNatCmmTop (CmmProc Nothing lbl (ListGraph [])) = pprLabel lbl
 
-pprNatCmmTop (CmmProc info lbl (ListGraph blocks)) = 
+ -- special case for code without an info table:
+pprNatCmmTop (CmmProc Nothing lbl (ListGraph blocks)) = 
   pprSectionHeader Text $$
-  (if null info then -- blocks guaranteed not null, so label needed
-       pprLabel lbl
-   else
+  pprLabel lbl $$ -- blocks guaranteed not null, so label needed
+  vcat (map pprBasicBlock blocks)
+
+pprNatCmmTop (CmmProc (Just (Statics info_lbl info)) _entry_lbl (ListGraph blocks)) = 
+  pprSectionHeader Text $$
+  (
 #if HAVE_SUBSECTIONS_VIA_SYMBOLS
-            pprCLabel_asm (mkDeadStripPreventer $ entryLblToInfoLbl lbl)
-                <> char ':' $$
+       pprCLabel_asm (mkDeadStripPreventer info_lbl)
+           <> char ':' $$
 #endif
        vcat (map pprData info) $$
-       pprLabel (entryLblToInfoLbl lbl)
+       pprLabel info_lbl
   ) $$
   vcat (map pprBasicBlock blocks)
      -- above: Even the first block gets a label, because with branch-chain
@@ -78,12 +82,10 @@ pprNatCmmTop (CmmProc info lbl (ListGraph blocks)) =
         -- from the entry code to a label on the _top_ of of the info table,
         -- so that the linker will not think it is unreferenced and dead-strip
         -- it. That's why the label is called a DeadStripPreventer (_dsp).
-  $$ if not (null info)
-		    then text "\t.long "
-		      <+> pprCLabel_asm (entryLblToInfoLbl lbl)
-		      <+> char '-'
-		      <+> pprCLabel_asm (mkDeadStripPreventer $ entryLblToInfoLbl lbl)
-		    else empty
+  $$ text "\t.long "
+	<+> pprCLabel_asm info_lbl
+	<+> char '-'
+	<+> pprCLabel_asm (mkDeadStripPreventer info_lbl)
 #endif
 
 
diff --git a/compiler/nativeGen/RegAlloc/Liveness.hs b/compiler/nativeGen/RegAlloc/Liveness.hs
index a6a3724bfa..0f9220de8f 100644
--- a/compiler/nativeGen/RegAlloc/Liveness.hs
+++ b/compiler/nativeGen/RegAlloc/Liveness.hs
@@ -158,7 +158,7 @@ data Liveness
 -- | Stash regs live on entry to each basic block in the info part of the cmm code.
 data LiveInfo
 	= LiveInfo
-		[CmmStatic]				-- cmm static stuff
+		(Maybe CmmStatics)			-- cmm info table static stuff
 		(Maybe BlockId)				-- id of the first block
 		(Maybe (BlockMap RegSet))		-- argument locals live on entry to this block
 		(Map BlockId (Set Int))			-- stack slots live on entry to this block
@@ -212,8 +212,8 @@ instance Outputable instr
 		 | otherwise		= name <> (hcat $ punctuate space $ map ppr $ uniqSetToList regs)
 
 instance Outputable LiveInfo where
-	ppr (LiveInfo static firstId liveVRegsOnEntry liveSlotsOnEntry)
-		=  (vcat $ map ppr static)
+	ppr (LiveInfo mb_static firstId liveVRegsOnEntry liveSlotsOnEntry)
+		=  (maybe empty ppr mb_static)
 		$$ text "# firstId          = " <> ppr firstId
 		$$ text "# liveVRegsOnEntry = " <> ppr liveVRegsOnEntry
 		$$ text "# liveSlotsOnEntry = " <> text (show liveSlotsOnEntry)
diff --git a/compiler/nativeGen/SPARC/Ppr.hs b/compiler/nativeGen/SPARC/Ppr.hs
index 7f3583f26c..aab700acc3 100644
--- a/compiler/nativeGen/SPARC/Ppr.hs
+++ b/compiler/nativeGen/SPARC/Ppr.hs
@@ -52,19 +52,23 @@ pprNatCmmTop (CmmData section dats) =
   pprSectionHeader section $$ pprDatas dats
 
  -- special case for split markers:
-pprNatCmmTop (CmmProc [] lbl (ListGraph [])) = pprLabel lbl
+pprNatCmmTop (CmmProc Nothing lbl (ListGraph [])) = pprLabel lbl
 
-pprNatCmmTop (CmmProc info lbl (ListGraph blocks)) = 
+ -- special case for code without info table:
+pprNatCmmTop (CmmProc Nothing lbl (ListGraph blocks)) = 
   pprSectionHeader Text $$
-  (if null info then -- blocks guaranteed not null, so label needed
-       pprLabel lbl
-   else
+  pprLabel lbl $$ -- blocks guaranteed not null, so label needed
+  vcat (map pprBasicBlock blocks)
+
+pprNatCmmTop (CmmProc (Just (Statics info_lbl info)) _entry_lbl (ListGraph blocks)) = 
+  pprSectionHeader Text $$
+  (
 #if HAVE_SUBSECTIONS_VIA_SYMBOLS
-            pprCLabel_asm (mkDeadStripPreventer $ entryLblToInfoLbl lbl)
-                <> char ':' $$
+       pprCLabel_asm (mkDeadStripPreventer info_lbl)
+           <> char ':' $$
 #endif
        vcat (map pprData info) $$
-       pprLabel (entryLblToInfoLbl lbl)
+       pprLabel info_lbl
   ) $$
   vcat (map pprBasicBlock blocks)
      -- above: Even the first block gets a label, because with branch-chain
@@ -76,12 +80,10 @@ pprNatCmmTop (CmmProc info lbl (ListGraph blocks)) =
         -- from the entry code to a label on the _top_ of of the info table,
         -- so that the linker will not think it is unreferenced and dead-strip
         -- it. That's why the label is called a DeadStripPreventer (_dsp).
-  $$ if not (null info)
-		    then text "\t.long "
-		      <+> pprCLabel_asm (entryLblToInfoLbl lbl)
-		      <+> char '-'
-		      <+> pprCLabel_asm (mkDeadStripPreventer $ entryLblToInfoLbl lbl)
-		    else empty
+  $$ text "\t.long "
+	<+> pprCLabel_asm info_lbl
+	<+> char '-'
+	<+> pprCLabel_asm (mkDeadStripPreventer info_lbl)
 #endif
 
 
diff --git a/compiler/nativeGen/X86/Ppr.hs b/compiler/nativeGen/X86/Ppr.hs
index 10af5ef8c1..5762cd93d5 100644
--- a/compiler/nativeGen/X86/Ppr.hs
+++ b/compiler/nativeGen/X86/Ppr.hs
@@ -54,19 +54,24 @@ pprNatCmmTop (CmmData section dats) =
   pprSectionHeader section $$ pprDatas dats
 
  -- special case for split markers:
-pprNatCmmTop (CmmProc [] lbl (ListGraph [])) = pprLabel lbl
+pprNatCmmTop (CmmProc Nothing lbl (ListGraph [])) = pprLabel lbl
 
-pprNatCmmTop (CmmProc info lbl (ListGraph blocks)) =
+ -- special case for code without info table:
+pprNatCmmTop (CmmProc Nothing lbl (ListGraph blocks)) =
   pprSectionHeader Text $$
-  (if null info then -- blocks guaranteed not null, so label needed
-       pprLabel lbl
-   else
+  pprLabel lbl $$ -- blocks guaranteed not null, so label needed
+  vcat (map pprBasicBlock blocks) $$
+  pprSizeDecl lbl
+
+pprNatCmmTop (CmmProc (Just (Statics info_lbl info)) _entry_lbl (ListGraph blocks)) =
+  pprSectionHeader Text $$
+  (
 #if HAVE_SUBSECTIONS_VIA_SYMBOLS
-            pprCLabel_asm (mkDeadStripPreventer $ entryLblToInfoLbl lbl)
-                <> char ':' $$
+       pprCLabel_asm (mkDeadStripPreventer info_lbl)
+           <> char ':' $$
 #endif
        vcat (map pprData info) $$
-       pprLabel (entryLblToInfoLbl lbl)
+       pprLabel info_lbl
   ) $$
   vcat (map pprBasicBlock blocks)
      -- above: Even the first block gets a label, because with branch-chain
@@ -78,14 +83,12 @@ pprNatCmmTop (CmmProc info lbl (ListGraph blocks)) =
         -- from the entry code to a label on the _top_ of of the info table,
         -- so that the linker will not think it is unreferenced and dead-strip
         -- it. That's why the label is called a DeadStripPreventer (_dsp).
-  $$ if not (null info)
-                    then text "\t.long "
-                      <+> pprCLabel_asm (entryLblToInfoLbl lbl)
-                      <+> char '-'
-                      <+> pprCLabel_asm (mkDeadStripPreventer $ entryLblToInfoLbl lbl)
-                    else empty
+  $$ text "\t.long "
+       <+> pprCLabel_asm info_lbl
+       <+> char '-'
+       <+> pprCLabel_asm (mkDeadStripPreventer info_lbl)
 #endif
-   $$ pprSizeDecl (if null info then lbl else entryLblToInfoLbl lbl)
+   $$ pprSizeDecl info_lbl
 
 -- | Output the ELF .size directive.
 pprSizeDecl :: CLabel -> Doc