[PATCH] D121355: [SelectionDAG] Fold shift constants into cmp

[Allen zhong via Phabricator via llvm-commits]

Allen marked an inline comment as done.
Allen added a comment.

ping? @craig.topper



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Comment at: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp:4552
+            // Replace C1 with (NewC << ShiftBits) is legal
+            // X <  C1     -> X <  (NewC << ShiftBits)
+            // X >= C1     -> X >= (NewC << ShiftBits)
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craig.topper wrote:
> The first two cases never happen do they?
> 
> In those cases `C1 == NewC << ShiftBits` and we already checked  isLegalICmpImmediate on line 4500.
Yes, thanks very much! 

I think AndRHS->getAPIntValue().isPowerOf2() will be matched, so I update the comment.


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Comment at: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp:4552
+            // Replace C1 with (NewC << ShiftBits) is legal
+            // X <  C1     -> X <  (NewC << ShiftBits)
+            // X >= C1     -> X >= (NewC << ShiftBits)
----------------
Allen wrote:
> craig.topper wrote:
> > The first two cases never happen do they?
> > 
> > In those cases `C1 == NewC << ShiftBits` and we already checked  isLegalICmpImmediate on line 4500.
> Yes, thanks very much! 
> 
> I think AndRHS->getAPIntValue().isPowerOf2() will be matched, so I update the comment.
hi, @craig.topper:
   I had update the comment, do you have other suggestion ?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D121355/new/

https://reviews.llvm.org/D121355