[llvm] [VectorCombine] Fold bitcast(bitreverse.v8i8(bitcast(IntTy))) into bswap+bitreverse (PR #209037)

[Simon Pilgrim via llvm-commits]

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@@ -6118,6 +6118,45 @@ bool VectorCombine::foldBitcastOfVPLoad(Instruction &I) {
 ///   bitreverse(bswap(x)) --> bitcast(bitreverse(bitcast(x)))
 bool VectorCombine::foldBitOrderReverseAndSwap(Instruction &I) {
   Value *X;
+
+  if (match(&I, m_BitCast(m_Intrinsic<Intrinsic::bitreverse>(
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RKSimon wrote:

Add a brief description, also you can use PatternMatch::m_BitReverse():
```suggestion
  if (match(&I, m_BitCast(m_BitReverse(
```

https://github.com/llvm/llvm-project/pull/209037