[Mlir-commits] [mlir] [mlir][spirv] Support poison index when converting vector.insert/extract (PR #125560)

[Andrea Faulds]

================
@@ -154,14 +174,26 @@ struct VectorExtractOpConvert final
     }
 
     if (std::optional<int64_t> id =
-            getConstantIntValue(extractOp.getMixedPosition()[0]))
-      rewriter.replaceOpWithNewOp<spirv::CompositeExtractOp>(
-          extractOp, dstType, adaptor.getVector(),
-          rewriter.getI32ArrayAttr(id.value()));
-    else
+            getConstantIntValue(extractOp.getMixedPosition()[0])) {
+      // TODO: It would be better to apply the ub.poison folding for this case
+      //       unconditionally, and have a specific SPIR-V lowering for it,
+      //       rather than having to handle it here.
----------------
andfau-amd wrote:

Ahh, no: `legalizeWithFold` calls `tryFold`, `tryFold` calls `ExtractOp::fold`, `ExtractOp::fold` calls `foldPoisonIndexInsertExtractOp`, and a poison attribute is generated, but then `tryFold` calls `VectorDialect::materializeConstant` and somewhere in there, the poison is rejected. Apparently, `VectorDialect::materializeConstant` calls `arith::ConstantOp::materialize`; maybe I just need to add a path to it that calls the UB dialect equivalent?

https://github.com/llvm/llvm-project/pull/125560