[llvm] [AMDGPU][ISEL] Use target specific hook to block narrowing insert-extract sub-vector (PR #201056)

[Krzysztof Drewniak via llvm-commits]

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@@ -27207,6 +27207,13 @@ static SDValue narrowInsertExtractVectorBinOp(EVT SubVT, SDValue BinOp,
   if (!Sub0 || !Sub1)
     return SDValue();
 
+  // Every user of the wide binop must be an EXTRACT_SUBVECTOR; otherwise the
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krzysz00 wrote:

This feels very narrow somehow

https://github.com/llvm/llvm-project/pull/201056