[PATCH] D60156: [X86] Use FILD/FIST to implement i64 atomic load on 32-bit targets with X87, but no SSE2

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: efriedma, RKSimon, spatel, reames, jfb.
Herald added subscribers: dexonsmith, hiraditya.
Herald added a project: LLVM.

If we have X87, but not SSE2 we can atomicaly load an i64 value into the significand of an 80-bit extended precision x87 register using fild. We can then use a fist instruction to convert it back to an i64 integer and store it to a stack temporary. From there we can do two 32-bit loads to get the value into integer registers without worrying about atomicness.

This matches what gcc and icc do for this case and removes an existing FIXME.


https://reviews.llvm.org/D60156

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/lib/Target/X86/X86ISelLowering.h
  llvm/lib/Target/X86/X86InstrFPStack.td
  llvm/test/CodeGen/X86/atomic-load-store-wide.ll
  llvm/test/CodeGen/X86/atomic-mi.ll
  llvm/test/CodeGen/X86/atomic-non-integer.ll
  llvm/test/CodeGen/X86/misched_phys_reg_assign_order.ll

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