[commit: ghc] master: Dwarf: Produce {low, high}_pc attributes for compilation units (cbf58a2)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/cbf58a217785acf519a3129916a5e9bb98a7b268/ghc

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

commit cbf58a217785acf519a3129916a5e9bb98a7b268
Author: Ben Gamari <bgamari.foss at gmail.com>
Date:   Sat Aug 29 12:24:54 2015 +0200

    Dwarf: Produce {low,high}_pc attributes for compilation units
    
    Some libraries (e.g. elfutils) need these otherwise they ignore our
    DWARF annotations.
    
    Test Plan: Test with elfutils' `readelf --debug-dump=cu_index`
    
    Reviewers: scpmw, austin
    
    Subscribers: thomie
    
    Differential Revision: https://phabricator.haskell.org/D1173


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

cbf58a217785acf519a3129916a5e9bb98a7b268
 compiler/nativeGen/Dwarf.hs       | 6 +++++-
 compiler/nativeGen/Dwarf/Types.hs | 9 ++++++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/compiler/nativeGen/Dwarf.hs b/compiler/nativeGen/Dwarf.hs
index 34f1ed6..273949e 100644
--- a/compiler/nativeGen/Dwarf.hs
+++ b/compiler/nativeGen/Dwarf.hs
@@ -30,6 +30,7 @@ import qualified Compiler.Hoopl as H
 -- | Generate DWARF/debug information
 dwarfGen :: DynFlags -> ModLocation -> UniqSupply -> [DebugBlock]
             -> IO (SDoc, UniqSupply)
+dwarfGen _  _      us [] = return (empty, us)
 dwarfGen df modLoc us blocks = do
 
   -- Convert debug data structures to DWARF info records
@@ -43,6 +44,8 @@ dwarfGen df modLoc us blocks = do
         , dwName = fromMaybe "" (ml_hs_file modLoc)
         , dwCompDir = addTrailingPathSeparator compPath
         , dwProducer = cProjectName ++ " " ++ cProjectVersion
+        , dwLowLabel = dblCLabel $ head procs
+        , dwHighLabel = mkAsmTempEndLabel $ dblCLabel $ last procs
         , dwLineLabel = dwarfLineLabel
         }
 
@@ -57,7 +60,8 @@ dwarfGen df modLoc us blocks = do
   let abbrevSct = pprAbbrevDecls haveSrc
 
   -- .debug_info section: Information records on procedures and blocks
-  let (unitU, us') = takeUniqFromSupply us
+  let -- unique to identify start and end compilation unit .debug_inf
+      (unitU, us') = takeUniqFromSupply us
       infoSct = vcat [ dwarfInfoSection
                      , compileUnitHeader unitU
                      , pprDwarfInfo haveSrc dwarfUnit
diff --git a/compiler/nativeGen/Dwarf/Types.hs b/compiler/nativeGen/Dwarf/Types.hs
index f9262b4..9a600bd 100644
--- a/compiler/nativeGen/Dwarf/Types.hs
+++ b/compiler/nativeGen/Dwarf/Types.hs
@@ -44,6 +44,8 @@ data DwarfInfo
                      , dwName :: String
                      , dwProducer :: String
                      , dwCompDir :: String
+                     , dwLowLabel :: CLabel
+                     , dwHighLabel :: CLabel
                      , dwLineLabel :: LitString }
   | DwarfSubprogram { dwChildren :: [DwarfInfo]
                     , dwName :: String
@@ -82,6 +84,8 @@ pprAbbrevDecls haveDebugLine =
        , (dW_AT_language, dW_FORM_data4)
        , (dW_AT_comp_dir, dW_FORM_string)
        , (dW_AT_use_UTF8, dW_FORM_flag_present)  -- not represented in body
+       , (dW_AT_low_pc,   dW_FORM_addr)
+       , (dW_AT_high_pc,  dW_FORM_addr)
        ] ++
        (if haveDebugLine
         then [ (dW_AT_stmt_list, dW_FORM_data4) ]
@@ -112,12 +116,15 @@ pprDwarfInfo haveSrc d
 -- that the binary format of this is paramterized in @abbrevDecls@ and
 -- has to be kept in synch.
 pprDwarfInfoOpen :: Bool -> DwarfInfo -> SDoc
-pprDwarfInfoOpen haveSrc (DwarfCompileUnit _ name producer compDir lineLbl) =
+pprDwarfInfoOpen haveSrc (DwarfCompileUnit _ name producer compDir lowLabel
+                                           highLabel lineLbl) =
   pprAbbrev DwAbbrCompileUnit
   $$ pprString name
   $$ pprString producer
   $$ pprData4 dW_LANG_Haskell
   $$ pprString compDir
+  $$ pprWord (ppr lowLabel)
+  $$ pprWord (ppr highLabel)
   $$ if haveSrc
      then sectionOffset lineLbl dwarfLineLabel
      else empty