[mlir] add complex type to getZeroAttr

[aartbik]

Summary

Fixes issue encountered with <sparse> complex constant
https://github.com/llvm/llvm-project/issues/56428

[aartbik]

mlir/lib/IR/BuiltinAttributes.cpp

1592

@rriddle : is this an acceptable solution? do zero attributes need more, like a named attribute or something like that?

[rriddle]

mlir/lib/IR/BuiltinAttributes.cpp

1592

Nah, this looks fine for the most part. This should just return whatever the agreed upon attribute interpretation of the type is.

1595

This will fail on integer elements.

[aartbik]

Thanks for having such a quick look.

mlir/lib/IR/BuiltinAttributes.cpp

1595

Good point yes!

[aartbik]

int/fp as element inside complex

mlir/lib/IR/BuiltinAttributes.cpp

 /// Get a zero attribute for the given attribute type.
 Attribute SparseElementsAttr::getZeroAttr() const {
   auto eltType = getElementType();
 
   // Handle floating point elements.
   if (eltType.isa<FloatType>())
     return FloatAttr::get(eltType, 0);
 
+  // Handle complex elements.
+  if (auto complexTy = eltType.dyn_cast<ComplexType>()) {
+    auto eltType = complexTy.getElementType();
+    Attribute zero;
+    if (eltType.isa<FloatType>())
+      zero = FloatAttr::get(eltType, 0);
+    else // must be integer
+      zero = IntegerAttr::get(eltType, 0);
+    return ArrayAttr::get(complexTy.getContext(),
+                          ArrayRef<Attribute>{zero, zero});
+  }
+
   // Handle string type.
   if (getValues().isa<DenseStringElementsAttr>())
     return StringAttr::get("", eltType);
 
   // Otherwise, this is an integer.
   return IntegerAttr::get(eltType, 0);
 }
 

mlir/test/Integration/Dialect/LLVMIR/CPU/test-complex-sparse-constant.mlir

+// RUN: mlir-opt %s --convert-memref-to-llvm | \
+// RUN:   mlir-cpu-runner -e entry -entry-point-result=void
+
+//
+// Code should not crash on the complex32 sparse constant.
+//
+module attributes {llvm.data_layout = ""} {
+  memref.global "private" constant @"__constant_32xcomplex<f32>_0" : memref<32xcomplex<f32>> =
+     sparse<[[1], [28], [31]],
+            [(1.000000e+00,0.000000e+00), (2.000000e+00,0.000000e+00), (3.000000e+00,0.000000e+00)]
+      > {alignment = 128 : i64}
+  llvm.func @entry() {
+     %0 = memref.get_global @"__constant_32xcomplex<f32>_0" : memref<32xcomplex<f32>>
+     llvm.return
+  }
+}