[mlir] Fix adding wrong operand value in `promoteMemRefDescriptors`.

[pifon2a]

Summary

The bug was not noticed because we didn't have a lot of custom type conversions
directly to LLVM dialect.

[ftynse]

Thanks!

[mehdi_amini]

Can you add a test please?

[pifon2a]

In D85192#2195280, @mehdi_amini wrote:

Can you add a test please?

It looks like it would require using TestDialect and writing a test pass from test dialect to llvm. Could there be a simpler way of testing this?

[ftynse]

It looks like it would require using TestDialect and writing a test pass from test dialect to llvm. Could there be a simpler way of testing this?

How did you stumble upon this? I think this function is called when an std.call is converted, so it should be sufficient to test that an std.call to a function that takes a mix of memrefs and scalars as arguments.

[pifon2a]

In D85192#2196724, @ftynse wrote:

It looks like it would require using TestDialect and writing a test pass from test dialect to llvm. Could there be a simpler way of testing this?

How did you stumble upon this? I think this function is called when an std.call is converted, so it should be sufficient to test that an std.call to a function that takes a mix of memrefs and scalars as arguments.

The mix of memrefs and scalars (with STD types) does not do the trick. I stumbled upon this bug when I tried to call a function that has a custom non-std type. In my case it was !tf_framework.op_kernel_context.

mlir/lib/Conversion/StandardToLLVM/StandardToLLVM.cpp

for (auto it : llvm::zip(opOperands, operands)) {
     }
     if (auto memrefType = operand.getType().dyn_cast<MemRefType>()) {
       MemRefDescriptor::unpack(builder, loc, llvmOperand,
                                operand.getType().cast<MemRefType>(),
                                promotedOperands);
       continue;
     }
 
-    promotedOperands.push_back(operand);
+    promotedOperands.push_back(llvmOperand);
   }
   return promotedOperands;
 }
 
 namespace {
 /// A pass converting MLIR operations into the LLVM IR dialect.
 struct LLVMLoweringPass : public ConvertStandardToLLVMBase<LLVMLoweringPass> {
   LLVMLoweringPass() = default;