[llvm] [GlobalIsel][NFC] Fix LLT Propagation (PR #119587)

[Matt Arsenault via llvm-commits]

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@@ -5347,9 +5347,9 @@ LegalizerHelper::fewerElementsBitcast(MachineInstr &MI, unsigned int TypeIdx,
 
   auto [DstReg, DstTy, SrcReg, SrcTy] = MI.getFirst2RegLLTs();
 
-  unsigned SrcScalSize = SrcTy.getScalarSizeInBits();
-  LLT SrcNarrowTy =
-      LLT::fixed_vector(NarrowTy.getSizeInBits() / SrcScalSize, SrcScalSize);
+  unsigned NewElemCount =
+      NarrowTy.getSizeInBits() / SrcTy.getScalarSizeInBits();
+  LLT SrcNarrowTy = LLT::fixed_vector(NewElemCount, SrcTy.getElementType());
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arsenm wrote:

I think this could use LLT::divide 

https://github.com/llvm/llvm-project/pull/119587