[mlir][SCFToEmitC] Don't convert unsupported types in EmitC

[CoTinker]

This PR adds check for unsupported types in emitc, which fixes a crash. Fixes #131442.

[llvmbot]

@llvm/pr-subscribers-mlir-emitc

@llvm/pr-subscribers-mlir

Author: Longsheng Mou (CoTinker)

Changes

This PR adds check for unsupported types in emitc, which fixes a crash. Fixes #131442.

---

Full diff: https://github.com/llvm/llvm-project/pull/131786.diff

2 Files Affected:

• (modified) mlir/lib/Conversion/SCFToEmitC/SCFToEmitC.cpp (+5-1)
• (added) mlir/test/Conversion/SCFToEmitC/scf-to-emitc-failed.mlir (+10)

diff --git a/mlir/lib/Conversion/SCFToEmitC/SCFToEmitC.cpp b/mlir/lib/Conversion/SCFToEmitC/SCFToEmitC.cpp
index 92523ca4f12b2..6f57703bf17b3 100644
--- a/mlir/lib/Conversion/SCFToEmitC/SCFToEmitC.cpp
+++ b/mlir/lib/Conversion/SCFToEmitC/SCFToEmitC.cpp
@@ -322,7 +322,11 @@ void SCFToEmitCPass::runOnOperation() {
   // Fallback converter
   // See note https://mlir.llvm.org/docs/DialectConversion/#type-converter
   // Type converters are called most to least recently inserted
-  typeConverter.addConversion([](Type t) { return t; });
+  typeConverter.addConversion([](Type type) -> std::optional<Type> {
+    if (emitc::isSupportedEmitCType(type))
+      return type;
+    return {};
+  });
   populateEmitCSizeTTypeConversions(typeConverter);
   populateSCFToEmitCConversionPatterns(patterns, typeConverter);
 
diff --git a/mlir/test/Conversion/SCFToEmitC/scf-to-emitc-failed.mlir b/mlir/test/Conversion/SCFToEmitC/scf-to-emitc-failed.mlir
new file mode 100644
index 0000000000000..02c27deaa7a13
--- /dev/null
+++ b/mlir/test/Conversion/SCFToEmitC/scf-to-emitc-failed.mlir
@@ -0,0 +1,10 @@
+// RUN: mlir-opt -convert-scf-to-emitc %s -split-input-file -verify-diagnostics
+
+func.func @unsupported_type_vector(%arg0 : index, %arg1 : index, %arg2 : index) -> vector<3xindex> {
+  %zero = arith.constant dense<0> : vector<3xindex>
+  // expected-error@+1 {{failed to legalize operation 'scf.for'}}
+  %r = scf.for %i0 = %arg0 to %arg1 step %arg2 iter_args(%acc = %zero) -> vector<3xindex> {
+    scf.yield %acc : vector<3xindex>
+  }
+  return %r : vector<3xindex>
+}

[marbre]

Thanks for picking this up! Just some minor remarks.

[josel-amd]

LGTM! Thanks!