Follow ForeignLabel changes in PPC NCG

[ghc-hetmet.git] / compiler / nativeGen / PIC.hs

diff --git a/compiler/nativeGen/PIC.hs b/compiler/nativeGen/PIC.hs
index 74c8bb3..a573b6b 100644 (file)
--- a/compiler/nativeGen/PIC.hs
+++ b/compiler/nativeGen/PIC.hs
@@ -64,12 +64,12 @@ import NCGMonad
 
 
 import Cmm
-import CLabel           ( CLabel, pprCLabel,
+import CLabel           ( CLabel, ForeignLabelSource(..), pprCLabel,
                           mkDynamicLinkerLabel, DynamicLinkerLabelInfo(..),
                           dynamicLinkerLabelInfo, mkPicBaseLabel,
                           labelDynamic, externallyVisibleCLabel )
 
-import CLabel           ( mkForeignLabel )
+import CLabel           ( mkForeignLabel, pprDebugCLabel )
 
 
 import StaticFlags     ( opt_PIC, opt_Static )
@@ -83,6 +83,7 @@ import DynFlags
 import FastString
 
 
+
 --------------------------------------------------------------------------------
 -- It gets called by the cmmToCmm pass for every CmmLabel in the Cmm
 -- code. It does The Right Thing(tm) to convert the CmmLabel into a
@@ -110,8 +111,12 @@ cmmMakeDynamicReference
              -> ReferenceKind     -- whether this is the target of a jump
              -> CLabel            -- the label
              -> m CmmExpr
-  
+
 cmmMakeDynamicReference dflags addImport referenceKind lbl
+   = cmmMakeDynamicReference' dflags addImport referenceKind lbl
+
+  
+cmmMakeDynamicReference' dflags addImport referenceKind lbl
   | Just _ <- dynamicLinkerLabelInfo lbl
   = return $ CmmLit $ CmmLabel lbl   -- already processed it, pass through
 
@@ -192,16 +197,40 @@ data LabelAccessStyle
 howToAccessLabel 
        :: DynFlags -> Arch -> OS -> ReferenceKind -> CLabel -> LabelAccessStyle
 
+
 -- Windows
--- 
--- We need to use access *exactly* those things that
--- are imported from a DLL via an __imp_* label.
--- There are no stubs for imported code.
+-- In Windows speak, a "module" is a set of objects linked into the
+-- same Portable Exectuable (PE) file. (both .exe and .dll files are PEs).
+--
+-- If we're compiling a multi-module program then symbols from other modules
+-- are accessed by a symbol pointer named __imp_SYMBOL. At runtime we have the
+-- following.
+--
+--   (in the local module)
+--     __imp_SYMBOL: addr of SYMBOL
+--
+--   (in the other module)
+--     SYMBOL: the real function / data.
+--
+-- To access the function at SYMBOL from our local module, we just need to
+-- dereference the local __imp_SYMBOL.
+--
+-- If opt_Static is set then we assume that all our code will be linked
+-- into the same .exe file. In this case we always access symbols directly, 
+-- and never use __imp_SYMBOL.
 --
 howToAccessLabel dflags _ OSMinGW32 _ lbl
+
+       -- Assume all symbols will be in the same PE, so just access them directly.
+       | opt_Static
+       = AccessDirectly
+       
+       -- If the target symbol is in another PE we need to access it via the
+       --      appropriate __imp_SYMBOL pointer.
        | labelDynamic (thisPackage dflags) lbl 
        = AccessViaSymbolPtr
 
+       -- Target symbol is in the same PE as the caller, so just access it directly.
        | otherwise
        = AccessDirectly
 
@@ -426,8 +455,10 @@ needImportedSymbols arch os
 -- position-independent code.
 gotLabel :: CLabel
 gotLabel 
-       = mkForeignLabel -- HACK: it's not really foreign
-               (fsLit ".LCTOC1") Nothing False IsData
+       -- HACK: this label isn't really foreign
+       = mkForeignLabel 
+               (fsLit ".LCTOC1") 
+               Nothing ForeignLabelInThisPackage IsData