[PATCH] D85965: [GlobalISel] Add a combine for ashr(shl x, c), c --> sext_inreg x, c'

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

Seems like it's missing a legality check, although I'm unclear on what the overall strategy for those is supposed to be



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Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:1895
+  Register Src;
+  if (!mi_match(MI.getOperand(0).getReg(), MRI,
+                m_GAShr(m_GShl(m_Reg(Src), m_ICst(ShlCst)), m_ICst(AshrCst))))
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Add a fixme for splat vectors?


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Comment at: llvm/test/CodeGen/AArch64/GlobalISel/prelegalizercombiner-ashr-shl-to-sext-inreg.mir:62
+
+...
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Could use some vector tests. I don't think m_ICst is smart enough to match splat vectors though. Adding the tests won't hurt for when that's solved.


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D85965