Do not #include external header files when compiling via C

This has several advantages:

 - -fvia-C is consistent with -fasm with respect to FFI declarations:
   both bind to the ABI, not the API.

 - foreign calls can now be inlined freely across module boundaries, since
   a header file is not required when compiling the call.

 - bootstrapping via C will be more reliable, because this difference
   in behavour between the two backends has been removed.

There is one disadvantage:

 - we get no checking by the C compiler that the FFI declaration
   is correct.

So now, the c-includes field in a .cabal file is always ignored by
GHC, as are header files specified in an FFI declaration.  This was
previously the case only for -fasm compilations, now it is also the
case for -fvia-C too.

1 files changed, 25 insertions, 1 deletions

diff --git a/compiler/cmm/CLabel.hs b/compiler/cmm/CLabel.hs
index 751575b0d1..a3c2634e35 100644
--- a/compiler/cmm/CLabel.hs
+++ b/compiler/cmm/CLabel.hs
@@ -105,6 +105,7 @@ module CLabel (
 
 	infoLblToEntryLbl, entryLblToInfoLbl,
 	needsCDecl, isAsmTemp, maybeAsmTemp, externallyVisibleCLabel,
+        isMathFun,
 	CLabelType(..), labelType, labelDynamic,
 
 	pprCLabel
@@ -462,7 +463,11 @@ needsCDecl ModuleRegdLabel		= False
 needsCDecl (StringLitLabel _)		= False
 needsCDecl (AsmTempLabel _)		= False
 needsCDecl (RtsLabel _)			= False
-needsCDecl (ForeignLabel _ _ _)		= False
+  -- RTS labels are declared in RTS header files.  Otherwise we'd need
+  -- to give types for each label reference in the RTS .cmm files
+  -- somehow; when generating .cmm code we know the types of labels (info, 
+  -- entry etc.) but for hand-written .cmm code we don't.
+needsCDecl l@(ForeignLabel _ _ _)	= not (isMathFun l)
 needsCDecl (CC_Label _)			= True
 needsCDecl (CCS_Label _)		= True
 needsCDecl (HpcTicksLabel _)            = True
@@ -478,6 +483,25 @@ maybeAsmTemp :: CLabel -> Maybe Unique
 maybeAsmTemp (AsmTempLabel uq) = Just uq
 maybeAsmTemp _ 	    	       = Nothing
 
+-- some labels have C prototypes in scope when compiling via C, because
+-- they are builtin to the C compiler.  For these labels we avoid
+-- generating our own C prototypes.
+isMathFun :: CLabel -> Bool
+isMathFun (ForeignLabel fs _ _) = fs `elem` math_funs
+  where
+  math_funs = [
+        FSLIT("pow"),    FSLIT("sin"),   FSLIT("cos"),
+        FSLIT("tan"),    FSLIT("sinh"),  FSLIT("cosh"),
+        FSLIT("tanh"),   FSLIT("asin"),  FSLIT("acos"),
+        FSLIT("atan"),   FSLIT("log"),   FSLIT("exp"),
+        FSLIT("sqrt"),   FSLIT("powf"),  FSLIT("sinf"),
+        FSLIT("cosf"),   FSLIT("tanf"),  FSLIT("sinhf"),
+        FSLIT("coshf"),  FSLIT("tanhf"), FSLIT("asinf"),
+        FSLIT("acosf"),  FSLIT("atanf"), FSLIT("logf"),
+        FSLIT("expf"),   FSLIT("sqrtf")
+   ]
+isMathFun _ = False
+
 -- -----------------------------------------------------------------------------
 -- Is a CLabel visible outside this object file or not?