[llvm] [mlir] [mlir][emitc] Ensure memref-to-emitc applies type converter to memref element types (PR #203742)

[Jeremy Kun via llvm-commits]

https://github.com/j2kun created https://github.com/llvm/llvm-project/pull/203742

None

>From 774cbe30e7a60914a0106e24dbadb9397eb31afa Mon Sep 17 00:00:00 2001
From: Jeremy Kun <jkun at google.com>
Date: Sat, 13 Jun 2026 19:41:23 -0700
Subject: [PATCH 1/2] memref-to-emitc: convert element type in memref.alloc
 lowering

---
 mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitC.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitC.cpp b/mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitC.cpp
index 693ebc7bc3bd0..cfe4f8bc23b3f 100644
--- a/mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitC.cpp
+++ b/mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitC.cpp
@@ -186,7 +186,12 @@ struct ConvertAlloc final : public OpConversionPattern<memref::AllocOp> {
     }
 
     Type sizeTType = emitc::SizeTType::get(rewriter.getContext());
-    Type elementType = memrefType.getElementType();
+    Type elementType =
+        getTypeConverter()->convertType(memrefType.getElementType());
+    if (!elementType) {
+      return rewriter.notifyMatchFailure(
+          loc, "failed to convert memref element type");
+    }
     IndexType indexType = rewriter.getIndexType();
     emitc::CallOpaqueOp sizeofElementOp = emitc::CallOpaqueOp::create(
         rewriter, loc, sizeTType, rewriter.getStringAttr("sizeof"),

>From 6d3034e53a2830db7d850a7bde1b9530fdb0566f Mon Sep 17 00:00:00 2001
From: Jeremy Kun <jkun at google.com>
Date: Sat, 13 Jun 2026 20:29:46 -0700
Subject: [PATCH 2/2] add test dialect memref-to-emitc test with custom type
 conversion

---
 .../Conversion/ConvertToEmitC/memref.mlir     | 12 ++++++++++++
 .../Dialect/Test/TestDialectInterfaces.cpp    | 19 +++++++++++++++++++
 .../mlir/test/BUILD.bazel                     |  2 ++
 3 files changed, 33 insertions(+)
 create mode 100644 mlir/test/Conversion/ConvertToEmitC/memref.mlir

diff --git a/mlir/test/Conversion/ConvertToEmitC/memref.mlir b/mlir/test/Conversion/ConvertToEmitC/memref.mlir
new file mode 100644
index 0000000000000..7e8993bdd0972
--- /dev/null
+++ b/mlir/test/Conversion/ConvertToEmitC/memref.mlir
@@ -0,0 +1,12 @@
+// RUN: mlir-opt -convert-to-emitc -split-input-file %s | FileCheck %s
+
+// CHECK-LABEL: emitc.func @test_memref_alloc()
+func.func @test_memref_alloc() {
+  // CHECK: %[[SIZEOF:.*]] = call_opaque "sizeof"() <{args = [!emitc.opaque<"TestElementT">]}> : () -> !emitc.size_t
+  // CHECK: %[[C10:.*]] = "emitc.constant"() <{value = 10 : index}> : () -> index
+  // CHECK: %[[BYTES:.*]] = mul %[[SIZEOF]], %[[C10]] : (!emitc.size_t, index) -> !emitc.size_t
+  // CHECK: %[[MALLOC:.*]] = call_opaque "malloc"(%[[BYTES]]) : (!emitc.size_t) -> !emitc.ptr<!emitc.opaque<"void">>
+  // CHECK: %[[CAST:.*]] = cast %[[MALLOC]] : !emitc.ptr<!emitc.opaque<"void">> to !emitc.ptr<!emitc.opaque<"TestElementT">>
+  %0 = memref.alloc() : memref<10x!test.memref_element>
+  return
+}
diff --git a/mlir/test/lib/Dialect/Test/TestDialectInterfaces.cpp b/mlir/test/lib/Dialect/Test/TestDialectInterfaces.cpp
index 1c9dbe1640687..04d956cce2eea 100644
--- a/mlir/test/lib/Dialect/Test/TestDialectInterfaces.cpp
+++ b/mlir/test/lib/Dialect/Test/TestDialectInterfaces.cpp
@@ -8,9 +8,13 @@
 
 #include "TestDialect.h"
 #include "TestOps.h"
+#include "TestTypes.h"
+#include "mlir/Conversion/ConvertToEmitC/ToEmitCInterface.h"
 #include "mlir/Dialect/ControlFlow/IR/ControlFlowOps.h"
+#include "mlir/Dialect/EmitC/IR/EmitC.h"
 #include "mlir/Interfaces/FoldInterfaces.h"
 #include "mlir/Reducer/ReductionPatternInterface.h"
+#include "mlir/Transforms/DialectConversion.h"
 #include "mlir/Transforms/InliningUtils.h"
 
 using namespace mlir;
@@ -432,6 +436,20 @@ struct TestReductionPatternInterface : public DialectReductionPatternInterface {
   }
 };
 
+struct TestToEmitCDialectInterface : public ConvertToEmitCPatternInterface {
+  explicit TestToEmitCDialectInterface(Dialect *dialect)
+      : ConvertToEmitCPatternInterface(dialect) {}
+
+  void populateConvertToEmitCConversionPatterns(
+      ConversionTarget &target, TypeConverter &typeConverter,
+      RewritePatternSet &patterns,
+      ::std::optional<bool> lowerToCpp) const final {
+    typeConverter.addConversion([](test::TestMemRefElementTypeType type) {
+      return emitc::OpaqueType::get(type.getContext(), "TestElementT");
+    });
+  }
+};
+
 } // namespace
 
 void TestDialect::registerInterfaces() {
@@ -440,4 +458,5 @@ void TestDialect::registerInterfaces() {
 
   addInterfaces<TestDialectFoldInterface, TestInlinerInterface,
                 TestReductionPatternInterface, TestBytecodeDialectInterface>();
+  addInterface<TestToEmitCDialectInterface>();
 }
diff --git a/utils/bazel/llvm-project-overlay/mlir/test/BUILD.bazel b/utils/bazel/llvm-project-overlay/mlir/test/BUILD.bazel
index f00a4eee0c6b2..0a0d373def04b 100644
--- a/utils/bazel/llvm-project-overlay/mlir/test/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/mlir/test/BUILD.bazel
@@ -401,12 +401,14 @@ cc_library(
         "//mlir:ControlFlowDialect",
         "//mlir:ControlFlowInterfaces",
         "//mlir:ControlFlowTransforms",
+        "//mlir:ConvertToEmitCInterface",
         "//mlir:DLTIDialect",
         "//mlir:DataLayoutInterfaces",
         "//mlir:DerivedAttributeOpInterface",
         "//mlir:DestinationStyleOpInterface",
         "//mlir:Dialect",
         "//mlir:DialectUtils",
+        "//mlir:EmitCDialect",
         "//mlir:FromLLVMIRTranslation",
         "//mlir:FuncDialect",
         "//mlir:FuncTransforms",