import MachInstrs
import NCGMonad ( NatM, getNewRegNat, getNewLabelNat )
-import CmdLineOpts ( opt_PIC )
+import CmdLineOpts ( opt_PIC, opt_Static )
import Pretty
import qualified Outputable
| opt_PIC && externallyVisibleCLabel lbl = AccessViaSymbolPtr
howToAccessLabel _ _ = AccessDirectly
-#elif linux_TARGET_OS && powerpc_TARGET_ARCH
--- PowerPC Linux
---
--- PowerPC Linux is just plain broken.
--- While it's theoretically possible to use GOT offsets larger
--- than 16 bit, the standard crt*.o files don't, which leads to
--- linker errors as soon as the GOT size exceeds 16 bit.
--- Also, the assembler doesn't support @gotoff labels.
--- In order to be able to use a larger GOT, we circumvent the
--- entire GOT mechanism and do it ourselves (this is what GCC does).
-
--- In this scheme, we need to do _all data references_ (even refs
--- to static data) via a SymbolPtr when we are generating PIC.
--- Luckily, the PLT works as expected, so we can simply access
--- dynamically linked code via the PLT.
+#elif linux_TARGET_OS && powerpc64_TARGET_ARCH
+-- ELF PPC64 (powerpc64-linux), AIX, MacOS 9, BeOS/PPC
-howToAccessLabel _ _ | not opt_PIC = AccessDirectly
-howToAccessLabel True lbl
- = if labelDynamic lbl then AccessViaStub
- else AccessDirectly
-howToAccessLabel False lbl
- = AccessViaSymbolPtr
+howToAccessLabel True lbl = AccessDirectly -- actually, .label instead of label
+howToAccessLabel _ lbl = AccessViaSymbolPtr
#elif linux_TARGET_OS
-- ELF (Linux)
--
+-- ELF tries to pretend to the main application code that dynamic linking does
+-- not exist. While this may sound convenient, it tends to mess things up in
+-- very bad ways, so we have to be careful when we generate code for the main
+-- program (-dynamic but no -fPIC).
+--
-- Indirect access is required for references to imported symbols
--- from position independent code.
--- It is always possible to access something indirectly,
--- even when it's not necessary.
-
--- For code, we can use a relative jump to a piece of
--- stub code instead (this allows lazy binding of imported symbols).
+-- from position independent code. It is also required from the main program
+-- when dynamic libraries containing Haskell code are used.
howToAccessLabel isJump lbl
- -- no PIC -> the dynamic linker does everything for us
- | not opt_PIC = AccessDirectly
- -- if it's not imported, we need no indirection
- -- ("foo" will end up being accessed as "foo@GOTOFF")
- | not (labelDynamic lbl) = AccessDirectly
+ -- no PIC -> the dynamic linker does everything for us;
+ -- if we don't dynamically link to Haskell code,
+ -- it actually manages to do so without messing thins up.
+ | not opt_PIC && opt_Static = AccessDirectly
+
#if !i386_TARGET_ARCH
-- for Intel, we temporarily disable the use of the
-- Procedure Linkage Table, because PLTs on intel require the
-- a jump through the PLT is made.
-- TODO: make the i386 NCG ensure this before jumping to a
-- CodeStub label, so we can remove this special case.
- | isJump = AccessViaStub
+
+ -- As long as we're in a shared library ourselves,
+ -- we can use the plt.
+ -- NOTE: We might want to disable this, because this
+ -- prevents -fPIC code from being linked statically.
+ | isJump && labelDynamic lbl && opt_PIC = AccessViaStub
+
+ -- TODO: it would be OK to access non-Haskell code via a stub
+-- | isJump && labelDynamic lbl && not isHaskellCode lbl = AccessViaStub
+
+ -- Using code stubs for jumps from the main program to an entry
+ -- label in a dynamic library is deadly; this will cause the dynamic
+ -- linker to replace all references (even data references) to that
+ -- label by references to the stub, so we won't find our info tables
+ -- any more.
+#endif
+
+ -- A dynamic label needs to be accessed via a symbol pointer.
+ -- NOTE: It would be OK to jump to foreign code via a PLT stub.
+ | labelDynamic lbl = AccessViaSymbolPtr
+
+#if powerpc_ARGET_ARCH
+ -- For PowerPC32 -fPIC, we have to access even static data
+ -- via a symbol pointer (see below for an explanation why
+ -- PowerPC32 Linux is especially broken).
+ | opt_PIC && not isJump = AccessViaSymbolPtr
#endif
- | otherwise = AccessViaSymbolPtr
+
+ | otherwise = AccessDirectly
#else
--
#elif powerpc_TARGET_ARCH && linux_TARGET_OS
--- For PowerPC linux, we don't do anything unless we're generating PIC.
-needImportedSymbols = opt_PIC
+-- PowerPC Linux
+--
+-- PowerPC Linux is just plain broken.
+-- While it's theoretically possible to use GOT offsets larger
+-- than 16 bit, the standard crt*.o files don't, which leads to
+-- linker errors as soon as the GOT size exceeds 16 bit.
+-- Also, the assembler doesn't support @gotoff labels.
+-- In order to be able to use a larger GOT, we circumvent the
+-- entire GOT mechanism and do it ourselves (this is what GCC does).
+
+-- In this scheme, we need to do _all data references_ (even refs
+-- to static data) via a SymbolPtr when we are generating PIC.
+
+-- We need to do this whenever we explicitly access something via
+-- a symbol pointer.
+needImportedSymbols = opt_PIC || not opt_Static
-- If we're generating PIC, we need to create our own "fake GOT".
projects / ghc-hetmet.git / blobdiff