[llvm] [SelectionDAG] Optimize BSWAP yet again once more (PR #165292)

[via llvm-commits]

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@@ -20157,28 +20174,28 @@ bool ARMTargetLowering::targetShrinkDemandedConstant(
 
   assert(VT == MVT::i32 && "Unexpected integer type");
 
+  // Exit early if we demand all bits.
+  if (DemandedBits.popcount() == 32)
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AZero13 wrote:

Just the copy paste of the logic in AArch64 

https://github.com/llvm/llvm-project/pull/165292