[Mlir-commits] [mlir] [mlir][Transforms] Dialect Conversion: No target mat. for 1:N replacement (PR #117513)

[Matthias Springer]

================
@@ -199,24 +211,34 @@ LLVMTypeConverter::LLVMTypeConverter(MLIRContext *ctx,
     // original memref type.
     return builder.create<UnrealizedConversionCastOp>(loc, resultType, desc)
         .getResult(0);
-  });
-  // Add generic source and target materializations to handle cases where
-  // non-LLVM types persist after an LLVM conversion.
-  addSourceMaterialization([&](OpBuilder &builder, Type resultType,
-                               ValueRange inputs, Location loc) {
-    if (inputs.size() != 1)
-      return Value();
+  };
 
-    return builder.create<UnrealizedConversionCastOp>(loc, resultType, inputs)
-        .getResult(0);
-  });
+  // Argument materializations convert from the new block argument types
+  // (multiple SSA values that make up a memref descriptor) back to the
+  // original block argument type.
+  addArgumentMaterialization(unrakedMemRefMaterialization);
+  addArgumentMaterialization(rankedMemRefMaterialization);
+  addSourceMaterialization(unrakedMemRefMaterialization);
+  addSourceMaterialization(rankedMemRefMaterialization);
+
+  // Bare pointer -> Packed MemRef descriptor
----------------
matthias-springer wrote:

> Could you explain why it is desireable to get rid of the argument materailization?

The purpose of an argument materialization is to convert N replacement values into 1 SSA value. It is a workaround around missing 1:N support in the conversion value mapping. In case of a 1:1 conversion, that workaround is not needed because the conversion value mapping can store 1:1 mappings directly.

This is also prefetching a bit from #116524, which removes argument materializations entirely. We are going to need the same type converter setup then.


https://github.com/llvm/llvm-project/pull/117513