[llvm] [instcombine] Scalarize operands of vector geps if possible (PR #145402)

[Philip Reames via llvm-commits]

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@@ -2983,6 +2983,7 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
   // For vector geps, use the generic demanded vector support.
   // Skip if GEP return type is scalable. The number of elements is unknown at
   // compile-time.
+  // TODO: exploit undef elements to decrease demanded bits
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preames wrote:

I decided to just remove the comment for the moment.  A variant of it might belong in the demanded elts logic itself, but even if so, this is the wrong spot for it.  

https://github.com/llvm/llvm-project/pull/145402