[PATCH] D118000: [AArch64][NFC] Abstracts shared behavior in MIPeepholeOpt for ADD, SUB, and AND.

Tue Jan 25 13:27:39 PST 2022

red1bluelost added inline comments.

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Comment at: llvm/lib/Target/AArch64/AArch64MIPeepholeOpt.cpp:354-355
+  T Imm = static_cast<T>(MovMI->getOperand(1).getImm()), Imm0, Imm1;
+  if (SubregToRegMI)
+    Imm &= 0xFFFFFFFF;
+  unsigned Opcode;
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dmgreen wrote:
> Do we have test case for this case with an ADD?
Turns out this was a very subtle but that I didn't catch in D117429. See example here: https://llvm.godbolt.org/z/Gnq1x8rh1

I added a test for this. We definitely want to have the `Imm &= 0xFFFF'FFFF` since assigning to `T Imm` will sign extend the value, not zero extend.

I guess in this case the revision is no longer NFC.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D118000/new/

https://reviews.llvm.org/D118000