[PATCH] D43214: [X86] Use EDI for retpoline when no scratch regs are left

[Reid Kleckner via Phabricator via llvm-commits]

rnk created this revision.
rnk added reviewers: chandlerc, dwmw2.
Herald added subscribers: hiraditya, kristof.beyls, javed.absar.

Instead of solving the hard problem of how to pass the callee to the indirect
jump thunk without a register, just use a CSR. At a call boundary, there's
nothing stopping us from using a CSR to hold the callee as long as we save and
restore it in the prologue.

Also, add tests for this mregparm=3 case. I wrote execution tests for
__llvm_retpoline_push, but they never got committed as lit tests, either
because I never rewrote them or because they got lost in merge conflicts.


https://reviews.llvm.org/D43214

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/lib/Target/X86/X86RetpolineThunks.cpp
  llvm/test/CodeGen/X86/retpoline-regparm.ll
  llvm/test/CodeGen/X86/retpoline.ll

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