[commit: ghc] master: Some Dwarf generation fixes (f85db75)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/f85db7567210bc2ff7036064a26d6ba29998f025/ghc

>---------------------------------------------------------------

commit f85db7567210bc2ff7036064a26d6ba29998f025
Author: Peter Wortmann <scpmw at leeds.ac.uk>
Date:   Thu Dec 18 21:11:23 2014 +0100

    Some Dwarf generation fixes
    
    - Make abbrev offset absolute on Non-Mac systems
    - Add another termination byte at the end of the abbrev section
      (readelf complains)
    - Scope combination was wrong for the simpler cases
    - Shouldn't have a "global/" in front of all scopes


>---------------------------------------------------------------

f85db7567210bc2ff7036064a26d6ba29998f025
 compiler/cmm/CmmNode.hs           | 11 +++++++----
 compiler/nativeGen/Dwarf.hs       |  4 ++--
 compiler/nativeGen/Dwarf/Types.hs | 18 ++++++++++++++++--
 3 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/compiler/cmm/CmmNode.hs b/compiler/cmm/CmmNode.hs
index b405360..0f26d37 100644
--- a/compiler/cmm/CmmNode.hs
+++ b/compiler/cmm/CmmNode.hs
@@ -660,6 +660,8 @@ instance Ord CmmTickScope where
 
 instance Outputable CmmTickScope where
   ppr GlobalScope     = text "global"
+  ppr (SubScope us GlobalScope)
+                      = ppr us
   ppr (SubScope us s) = ppr s <> char '/' <> ppr us
   ppr combined        = parens $ hcat $ punctuate (char '+') $
                         map (hcat . punctuate (char '/') . map ppr . reverse) $
@@ -675,10 +677,11 @@ isTickSubScope = cmp
         cmp s              (CombinedScope s1' s2') = cmp s s1' || cmp s s2'
         cmp (SubScope u s) s'@(SubScope u' _)      = u == u' || cmp s s'
 
--- | Combine two tick scopes. This smart constructor will catch cases
--- where one tick scope is a sub-scope of the other already.
+-- | Combine two tick scopes. The new scope should be sub-scope of
+-- both parameters. We simplfy automatically if one tick scope is a
+-- sub-scope of the other already.
 combineTickScopes :: CmmTickScope -> CmmTickScope -> CmmTickScope
 combineTickScopes s1 s2
-  | s1 `isTickSubScope` s2 = s2
-  | s2 `isTickSubScope` s1 = s1
+  | s1 `isTickSubScope` s2 = s1
+  | s2 `isTickSubScope` s1 = s2
   | otherwise              = CombinedScope s1 s2
diff --git a/compiler/nativeGen/Dwarf.hs b/compiler/nativeGen/Dwarf.hs
index 4f9bdb6..70fca4f 100644
--- a/compiler/nativeGen/Dwarf.hs
+++ b/compiler/nativeGen/Dwarf.hs
@@ -83,8 +83,8 @@ compileUnitHeader unitU = sdocWithPlatform $ \plat ->
   in vcat [ ptext (sLit "\t.long ") <> length  -- compilation unit size
           , ppr cuLabel <> colon
           , ptext (sLit "\t.word 3")           -- DWARF version
-          , pprDwWord (ptext dwarfAbbrevLabel <> char '-' <>
-                       ptext dwarfAbbrevLabel) -- pointer to our abbrevs
+          , pprDwWord (sectionOffset dwarfAbbrevLabel dwarfAbbrevLabel)
+                                               -- abbrevs offset
           , ptext (sLit "\t.byte ") <> ppr (platformWordSize plat) -- word size
           ]
 
diff --git a/compiler/nativeGen/Dwarf/Types.hs b/compiler/nativeGen/Dwarf/Types.hs
index 96fea0a..47e0bd1 100644
--- a/compiler/nativeGen/Dwarf/Types.hs
+++ b/compiler/nativeGen/Dwarf/Types.hs
@@ -14,6 +14,7 @@ module Dwarf.Types
   , pprLEBWord
   , pprLEBInt
   , wordAlign
+  , sectionOffset
   )
   where
 
@@ -94,7 +95,9 @@ pprAbbrevDecls haveDebugLine =
        [ (dW_AT_name, dW_FORM_string)
        , (dW_AT_low_pc, dW_FORM_addr)
        , (dW_AT_high_pc, dW_FORM_addr)
-       ]
+       ] $$
+     pprByte 0
+
 -- | Generate assembly for DWARF data
 pprDwarfInfo :: Bool -> DwarfInfo -> SDoc
 pprDwarfInfo haveSrc d
@@ -113,7 +116,7 @@ pprDwarfInfoOpen haveSrc (DwarfCompileUnit _ name producer compDir lineLbl) =
   $$ pprData4 dW_LANG_Haskell
   $$ pprString compDir
   $$ if haveSrc
-     then pprData4' (ptext lineLbl <> char '-' <> ptext dwarfLineLabel)
+     then pprData4' (sectionOffset lineLbl dwarfLineLabel)
      else empty
 pprDwarfInfoOpen _ (DwarfSubprogram _ name label) = sdocWithDynFlags $ \df ->
   pprAbbrev DwAbbrSubprogram
@@ -416,3 +419,14 @@ pprString = pprString' . hcat . map escape
                          char (intToDigit (ch `div` 64)) <>
                          char (intToDigit ((ch `div` 8) `mod` 8)) <>
                          char (intToDigit (ch `mod` 8))
+
+-- | Generate an offset into another section. This is tricky because
+-- this is handled differently depending on platform: Mac Os expects
+-- us to calculate the offset using assembler arithmetic. Meanwhile,
+-- GNU tools expect us to just reference the target directly, and will
+-- figure out on their own that we actually need an offset.
+sectionOffset :: LitString -> LitString -> SDoc
+sectionOffset target section = sdocWithPlatform $ \plat ->
+  case platformOS plat of
+    OSDarwin -> ptext target <> char '-' <> ptext section
+    _other   -> ptext target