[PATCH] D91108: [AArch64][GlobalISel] Select negative arithmetic immediates in manual selector

[Jessica Paquette via Phabricator via llvm-commits]

paquette created this revision.
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Previously, we only handled negative arithmetic immediates in the imported selector code.

Since we don't import code for, say, compares, we were missing opportunities for things like

  %cst:gpr(s64) = G_CONSTANT i64 -10
  %cmp:gpr(s32) = G_ICMP intpred(eq), %reg0(s64), %cst
  ->
  %adds = ADDSXri %reg0, 10, 0, implicit-def $nzcv
  %cmp = CSINCWr $wzr, $wzr, 1, implicit $nzcv

Instead, we would have to materialize the constant and emit a SUBS.

This adds support for selection like above for SUB, SUBS, ADD, and ADDS.

This is a 0.1% geomean code size improvement on SPECINT2000 at -Os.


https://reviews.llvm.org/D91108

Files:
  llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/opt-fold-compare.mir
  llvm/test/CodeGen/AArch64/GlobalISel/select-cmp.mir
  llvm/test/CodeGen/AArch64/GlobalISel/select-ptr-add.mir
  llvm/test/CodeGen/AArch64/GlobalISel/select-uaddo.mir
  llvm/test/CodeGen/AArch64/GlobalISel/tbz-sgt.mir

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