Return failure on failure in convertBlockSignature.

[stellaraccident]

Summary

This was causing a subsequent assert/crash when a type converter failed to convert a block argument.

[rriddle]

Is there a test that can cover this?

[stellaraccident]

In D110985#3037873, @rriddle wrote:

Is there a test that can cover this?

I'll check next week before landing. Was just in a debugging session with my code and found this/didn't want to lose it.

[stellaraccident]

Added test case.

mlir/lib/Transforms/Utils/DialectConversion.cpp

 FailureOr<Block *> ConversionPatternRewriterImpl::convertBlockSignature(
     Block *block, TypeConverter &converter,
     TypeConverter::SignatureConversion *conversion) {
   FailureOr<Block *> result =
       conversion ? argConverter.applySignatureConversion(
                        block, converter, *conversion, mapping, argReplacements)
                  : argConverter.convertSignature(block, converter, mapping,
                                                  argReplacements);
+  if (failed(result))
+    return failure();
   if (Block *newBlock = result.getValue()) {
     if (newBlock != block)
       blockActions.push_back(BlockAction::getTypeConversion(newBlock));
   }
   return result;
 }
 
 Block *ConversionPatternRewriterImpl::applySignatureConversion(

mlir/test/Transforms/test-legalize-type-conversion.mlir

func @test_signature_conversion_undo() {
   "test.signature_conversion_undo"() ({
   // CHECK: ^{{.*}}(%{{.*}}: f32):
   ^bb0(%arg0: f32):
     "test.type_consumer"(%arg0) : (f32) -> ()
     "test.return"(%arg0) : (f32) -> ()
   }) : () -> ()
   return
 }
+
+// -----
+
+// Should not segfault here but gracefully fail.
+// CHECK-LABEL: func @test_block_argument_not_converted
+func @test_block_argument_not_converted() {
+  "test.unsupported_block_arg_type"() ({
+    // NOTE: The test pass does not convert `index` types.
+    // CHECK: ^bb0({{.*}}: index):
+    ^bb0(%0 : index):
+      "test.return"(%0) : (index) -> ()
+  }) : () -> ()
+  return
+}