[PATCH] D27425: [AArch64] Fold some refilled/spilled subreg COPYs

[Geoff Berry via Phabricator via llvm-commits]

gberry created this revision.
gberry added reviewers: MatzeB, qcolombet.
gberry added a subscriber: llvm-commits.
Herald added subscribers: mcrosier, rengolin, aemerson.

Extend AArch64 foldMemoryOperandImpl() to handle folding spills of
subreg COPYs with read-undef defs like:

  %vreg0:sub_32<def,read-undef> = COPY %WZR; GPR64:%vreg0

by widening the spilled physical source reg and generating:

  STRXui %XZR <fi#0>

as well as folding refills of similar COPYs like:

  %vreg0:sub_32<def,read-undef> = COPY %vreg1; GPR64:%vreg0, GPR32:%vreg1

by generating:

  %vreg0:sub_32<def,read-undef> = LDRWui <fi#0>


https://reviews.llvm.org/D27425

Files:
  lib/Target/AArch64/AArch64InstrInfo.cpp
  lib/Target/AArch64/AArch64InstrInfo.h
  test/CodeGen/MIR/AArch64/spill-fold.mir

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