[llvm-commits] [PATCH] x86 code emitter improvements for object files

[Bruno Cardoso Lopes]

Hi all,

The X86CodeEmitter has the following behaviour:

1) When emiting displacements:
- Only use pc_relative relocations for x86_64 (globals, cstpools and jmptables)
- For x86, only uses pc_rel ou pic_re
This two items above do not always work for ELF.

2) RIP addressing:
The way emitMemModRMByte works now uses RIP relocation for all cases
where RegBase=0, IndexReg=0, and when the displacement needs relocation. And
for those cases, it will never generate a SIB byte + absolute
relocation, which ELF
needs.

3) The JIT can get the real address of cstpools and jmptables during
code emission,
but the same won't work for relocatable object files.

This patch try to solve the 3 problems above to properly emit elf
binaries for x86/x86_64. With
this changes applied (together with elf improvements I've not commited
yet) I was able
to run 209/243 (83%) of SinglesSources using ELF object files emited by LLC :)
and with no regressions for JIT.

The way the patch was done tries to ensure that no previous JIT code
emission mechanism will
be changed, trying to avoid loss in performance and new JIT bugs.

The patch also introduces a new x86 relocation type reloc_absolute_word_sext,
which is lowered to x86 elf reloc type R_X86_64_32S.

Please, review and comment :)

-- 
Bruno Cardoso Lopes
http://www.brunocardoso.cc
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