[PATCH] D15239: x86: add has lahf/sahf feature

[JF Bastien via llvm-commits]

jfb added a comment.

Follow-up to: http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20150810/293071.html

This patch isn't ready yet:

- It needs to be taught about which CPUs support LAHF/SAHF and which don't.
- Code generation also needs to change in `X86TargetLowering::ConvertCmpIfNecessary`.
- Some tests need to be added.

The following tests are currently failing, and may need to be updated:

  LLVM :: CodeGen/X86/2004-02-22-Casts.ll
  LLVM :: CodeGen/X86/2004-06-10-StackifierCrash.ll
  LLVM :: CodeGen/X86/2006-05-22-FPSetEQ.ll
  LLVM :: CodeGen/X86/2008-05-01-InvalidOrdCompare.ll
  LLVM :: CodeGen/X86/2009-02-12-SpillerBug.ll
  LLVM :: CodeGen/X86/2009-03-09-SpillerBug.ll
  LLVM :: CodeGen/X86/2012-08-28-UnsafeMathCrash.ll
  LLVM :: CodeGen/X86/2012-10-02-DAGCycle.ll
  LLVM :: CodeGen/X86/bitcast-int-to-vector.ll
  LLVM :: CodeGen/X86/block-placement.ll
  LLVM :: CodeGen/X86/cmovcmov.ll
  LLVM :: CodeGen/X86/cmpxchg-clobber-flags.ll
  LLVM :: CodeGen/X86/constpool.ll
  LLVM :: CodeGen/X86/crash.ll
  LLVM :: CodeGen/X86/fabs.ll
  LLVM :: CodeGen/X86/fp-stack-O0-crash.ll
  LLVM :: CodeGen/X86/fp-stack-compare.ll
  LLVM :: CodeGen/X86/fp-stack.ll
  LLVM :: CodeGen/X86/isnan.ll
  LLVM :: CodeGen/X86/peephole-na-phys-copy-folding.ll
  LLVM :: CodeGen/X86/scalar-fp-to-i64.ll
  LLVM :: CodeGen/X86/setuge.ll
  LLVM :: CodeGen/X86/stack-protector.ll
  LLVM :: CodeGen/X86/vec_fp_to_int.ll


http://reviews.llvm.org/D15239