import Unique ( Unique, getUnique )
import UniqSupply
import FastTypes
-#if darwin_TARGET_OS || (powerpc_TARGET_ARCH && linux_TARGET_OS)
import List ( groupBy, sortBy )
import CLabel ( pprCLabel )
-#endif
import ErrUtils ( dumpIfSet_dyn )
import CmdLineOpts ( DynFlags, DynFlag(..), dopt, opt_Static,
opt_EnsureSplittableC, opt_PIC )
split_marker = CmmProc [] mkSplitMarkerLabel [] []
-#if darwin_TARGET_OS || (powerpc_TARGET_ARCH && linux_TARGET_OS)
-- Generate "symbol stubs" for all external symbols that might
-- come from a dynamic library.
{- dyld_stubs imps = Pretty.vcat $ map pprDyldSymbolStub $
where doPpr lbl = (lbl, Pretty.render $ pprCLabel lbl astyle)
astyle = mkCodeStyle AsmStyle
-#else
- dyld_stubs imps = Pretty.empty
-#endif
#ifndef NCG_DEBUG
my_vcat sds = Pretty.vcat sds
dynamicLinkerLabelInfo, mkPicBaseLabel,
labelDynamic, externallyVisibleCLabel )
-#if powerpc_TARGET_ARCH && linux_TARGET_OS
+#if linux_TARGET_OS
import CLabel ( mkForeignLabel )
#endif
| otherwise = empty
-#elif powerpc_TARGET_ARCH && linux_TARGET_OS
+#elif linux_TARGET_OS && !powerpc32_TARGET_ARCH
--- PowerPC Linux
+-- ELF / Linux
+--
+-- In theory, we don't need to generate any stubs or symbol pointers
+-- by hand for Linux.
+--
+-- Reality differs from this in two areas.
--
--- 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.
+-- 1) If we just use a dynamically imported symbol directly in a read-only
+-- section of the main executable (as GCC does), ld generates R_*_COPY
+-- relocations, which are fundamentally incompatible with reversed info
+-- tables. Therefore, we need a table of imported addresses in a writable
+-- section.
+-- The "official" GOT mechanism (label@got) isn't intended to be used
+-- in position dependent code, so we have to create our own "fake GOT"
+-- when not opt_PCI && not opt_Static.
+--
+-- 2) 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 have to circumvent the
+-- entire GOT mechanism and do it ourselves (this is also what GCC does).
+
+
+-- When needImportedSymbols is defined,
+-- the NCG will keep track of all DynamicLinkerLabels it uses
+-- and output each of them using pprImportedSymbol.
+#if powerpc_TARGET_ARCH
+ -- PowerPC Linux: -fPIC or -dynamic
needImportedSymbols = opt_PIC || not opt_Static
+#else
+ -- i386 (and others?): -dynamic but not -fPIC
+needImportedSymbols = not opt_Static && not opt_PIC
+#endif
--- If we're generating PIC, we need to create our own "fake GOT".
-
+-- gotLabel
+-- The label used to refer to our "fake GOT" from
+-- position-independent code.
gotLabel = mkForeignLabel -- HACK: it's not really foreign
FSLIT(".LCTOC1") Nothing False
+-- pprGotDeclaration
+-- Output whatever needs to be output once per .s file.
-- The .LCTOC1 label is defined to point 32768 bytes into the table,
-- to make the most of the PPC's 16-bit displacements.
+-- Only needed for PIC.
-pprGotDeclaration = vcat [
+pprGotDeclaration
+ | not opt_PIC = Pretty.empty
+ | otherwise = vcat [
ptext SLIT(".section \".got2\",\"aw\""),
ptext SLIT(".LCTOC1 = .+32768")
]
-- We generate one .long literal for every symbol we import;
-- the dynamic linker will relocate those addresses.
-
+
pprImportedSymbol importedLbl
| Just (SymbolPtr, lbl) <- dynamicLinkerLabelInfo importedLbl
= vcat [
: ADD picReg picReg (RIReg tmp)
: insns)
return (CmmProc info lab params (b' : tail blocks) : gotOffset : statics)
-#else
-initializePicBase picReg proc = panic "initializePicBase"
+#elif i386_TARGET_ARCH && linux_TARGET_OS
--- TODO:
--- i386_TARGET_ARCH && linux_TARGET_OS:
--- generate something like:
+-- We cheat a bit here by defining a pseudo-instruction named FETCHGOT
+-- which pretty-prints as:
-- call 1f
-- 1: popl %picReg
-- addl __GLOBAL_OFFSET_TABLE__+.-1b, %picReg
--- It might be a good idea to use a FETCHPC pseudo-instruction (like for PowerPC)
--- in order to avoid having to create a new basic block.
--- ((FETCHPC reg) should pretty-print as call 1f; 1: popl reg)
+-- (See PprMach.lhs)
+
+initializePicBase picReg (CmmProc info lab params blocks : statics)
+ = return (CmmProc info lab params (b':tail blocks) : statics)
+ where BasicBlock bID insns = head blocks
+ b' = BasicBlock bID (FETCHGOT picReg : insns)
+
+#else
+initializePicBase picReg proc = panic "initializePicBase"
-- mingw32_TARGET_OS: not needed, won't be called
projects / ghc-hetmet.git / commitdiff