Address the last bit of relocation flag related divergence betweeen

LLVM and binutils.

With this patch, there are no functional differences between the .o
produced directly from LLVM versus the .s to .o via GNU as, for relocation tags
at least, for both PIC and non-PIC modes.

Because some non-PIC reloc tags are used (legally) on PIC, so IsPCRel flag is
necessary but not sufficient to determine whether the overall codegen mode is
PIC or not. Why is this necessary? There is an incompatibility of how relocs
are emitted in the .rodata section.  Binutils PIC likes to emit certain relocs
as section relative offsets.  Non-PIC does not do this.

So I added a hidden switch on the ELFObjectwriter "-arm-elf-force-pic" which
forces the objectwriter to pretend that all relocs are for PIC mode.


Todo: Activate ForceARMElfPIC to true if -relocation-model=pic is selected
on llc.

Todo: There are probably more issues for PIC mode on ARM/MC/ELF...

Todo: Existing tests in MC/ARM/elf-reloc*.ll need to be converted over to .s 
tests as well as expanded to cover the gamut.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131205 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 5 deletions

diff --git a/lib/MC/ELFObjectWriter.h b/lib/MC/ELFObjectWriter.h
index f1d514a899..7593099fb4 100644
--- a/lib/MC/ELFObjectWriter.h
+++ b/lib/MC/ELFObjectWriter.h
@@ -140,15 +140,18 @@ class ELFObjectWriter : public MCObjectWriter {
     unsigned ShstrtabIndex;
 
 
-    const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
-                                  const MCValue &Target,
-                                  const MCFragment &F) const;
+    virtual const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
+                                          const MCValue &Target,
+                                          const MCFragment &F,
+                                          const MCFixup &Fixup,
+                                          bool IsPCRel) const;
 
     // For arch-specific emission of explicit reloc symbol
     virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
                                            const MCValue &Target,
                                            const MCFragment &F,
-                                           bool IsBSS) const {
+                                           const MCFixup &Fixup,
+                                           bool IsPCRel) const {
       return NULL;
     }
 
@@ -380,11 +383,16 @@ class ELFObjectWriter : public MCObjectWriter {
     virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
                                            const MCValue &Target,
                                            const MCFragment &F,
-                                           bool IsBSS) const;
+                                           const MCFixup &Fixup,
+                                           bool IsPCRel) const;
 
     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                                   bool IsPCRel, bool IsRelocWithSymbol,
                                   int64_t Addend);
+  private:
+    unsigned GetRelocTypeInner(const MCValue &Target,
+                               const MCFixup &Fixup, bool IsPCRel) const;
+    
   };
 
   //===- MBlazeELFObjectWriter -------------------------------------------===//