[project @ 2004-10-07 15:54:03 by wolfgang]

Position Independent Code and Dynamic Linking Support, Part 1

This commit allows generation of position independent code (PIC) that fully supports dynamic linking on Mac OS X and PowerPC Linux.
Other platforms are not yet supported, and there is no support for actually linking or using dynamic libraries - so if you use the -fPIC or -dynamic code generation flags, you have to type your (platform-specific) linker command lines yourself.


nativeGen/PositionIndependentCode.hs:
New file. Look here for some more comments on how this works.

cmm/CLabel.hs:
Add support for DynamicLinkerLabels and PIC base labels - for use inside the NCG.
needsCDecl: Case alternative labels now need C decls, see the codeGen/CgInfoTbls.hs below for details

cmm/Cmm.hs:
Add CmmPicBaseReg (used in NCG),
and CmmLabelDiffOff (used in NCG and for offsets in info tables)

cmm/CmmParse.y:
support offsets in info tables

cmm/PprC.hs:
support CmmLabelDiffOff
Case alternative labels now need C decls (see the codeGen/CgInfoTbls.hs for details), so we need to pprDataExterns for info tables.

cmm/PprCmm.hs:
support CmmLabelDiffOff

codeGen/CgInfoTbls.hs:
no longer store absolute addresses in info tables, instead, we store offsets.
Also, for vectored return points, emit the alternatives _after_ the vector table. This is to work around a limitation in Apple's as, which refuses to handle label differences where one label is at the end of a section. Emitting alternatives after vector info tables makes sure this never happens in GHC generated code. Case alternatives now require prototypes in hc code, though (see changes in PprC.hs, CLabel.hs).

main/CmdLineOpts.lhs:
Add a new option, -fPIC.

main/DriverFlags.hs:
Pass the correct options for PIC to gcc, depending on the platform. Only for powerpc for now.

nativeGen/AsmCodeGen.hs:
Many changes...
Mac OS X-specific management of import stubs is no longer, it's now part of a general mechanism to handle such things for all platforms that need it (Darwin [both ppc and x86], Linux on ppc, and some platforms we don't support).
Move cmmToCmm into its own monad which can accumulate a list of imported symbols. Make it call cmmMakeDynamicReference at the right places.

nativeGen/MachCodeGen.hs:
nativeGen/MachInstrs.hs:
nativeGen/MachRegs.lhs:
nativeGen/PprMach.hs:
nativeGen/RegAllocInfo.hs:
Too many changes to enumerate here, PowerPC specific.

nativeGen/NCGMonad.hs:
NatM still tracks imported symbols, as more labels can be created during code generation (float literals, jump tables; on some platforms all data access has to go through the dynamic linking mechanism).

driver/mangler/ghc-asm.lprl:
Mangle absolute addresses in info tables to offsets.
Correctly pass through GCC-generated PIC for Mac OS X and powerpc linux.

includes/Cmm.h:
includes/InfoTables.h:
includes/Storage.h:
includes/mkDerivedConstants.c:
rts/GC.c:
rts/GCCompact.c:
rts/HeapStackCheck.cmm:
rts/Printer.c:
rts/RetainerProfile.c:
rts/Sanity.c:
Adapt to the fact that info tables now contain offsets.

rts/Linker.c:
Mac-specific: change machoInitSymbolsWithoutUnderscore to support PIC.

1 files changed, 14 insertions, 5 deletions

diff --git a/ghc/compiler/main/DriverFlags.hs b/ghc/compiler/main/DriverFlags.hs
index c09e43ad2d..b3bda23701 100644
--- a/ghc/compiler/main/DriverFlags.hs
+++ b/ghc/compiler/main/DriverFlags.hs
@@ -621,11 +621,20 @@ machdepCCOpts
       --     for "normal" programs, but it doesn't support register variable
       --     declarations.
       -- -mdynamic-no-pic:
-      --     As we don't support haskell code in shared libraries anyway,
-      --     we might as well turn of PIC code generation and save space and time.
-      --     This is completely optional.
-       = return ( ["-no-cpp-precomp","-mdynamic-no-pic"], [] )
-
+      --     Turn off PIC code generation to save space and time.
+      -- -fno-common:
+      --     Don't generate "common" symbols - these are unwanted
+      --     in dynamic libraries.
+
+        = if opt_PIC
+            then return ( ["-no-cpp-precomp", "-fno-common"],
+                          ["-fno-common"] )
+            else return ( ["-no-cpp-precomp", "-mdynamic-no-pic"],
+                          ["-mdynamic-no-pic"] )
+
+   | prefixMatch "powerpc" cTARGETPLATFORM && opt_PIC
+        = return ( ["-fPIC"], ["-fPIC"] )
+  
    | otherwise
 	= return ( [], [] )