[llvm] [AArch64] Combine PTEST_FIRST(PTRUE, CONCAT(A, B)) -> PTEST_FIRST(PTRUE, A) (PR #161384)

[Paul Walker via llvm-commits]

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@@ -1503,6 +1503,10 @@ AArch64InstrInfo::canRemovePTestInstr(MachineInstr *PTest, MachineInstr *Mask,
             getElementSizeForOpcode(PredOpcode))
       return PredOpcode;
 
+    if (PTest->getOpcode() == AArch64::PTEST_PP_FIRST &&
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paulwalker-arm wrote:

Perhaps add a comment to match the other cases?

https://github.com/llvm/llvm-project/pull/161384