[mlir][LLVM] Fix `DataLayoutTypeInterface` for opqaue pointers with non-default address space

[zero9178]

Summary

As a fallback mechanism, if no entry was supplied for a given address space, the size or alignment for a pointer type with the default address space is returned instead.
This code currently crashes with opaque pointers, as it tries to construct a typed pointer type from the opaque pointer type, leading to a null pointer dereference when fetching the element type.

This patch fixes the issue by handling the opaque pointer cases explicitly.

mlir/lib/Dialect/LLVMIR/IR/LLVMTypes.cpp

 LLVMPointerType::getTypeSizeInBits(const DataLayout &dataLayout,
                                    DataLayoutEntryListRef params) const {
   if (Optional<unsigned> size =
           getPointerDataLayoutEntry(params, *this, DLEntryPos::Size))
     return *size;
 
   // For other memory spaces, use the size of the pointer to the default memory
   // space.
+  if (isOpaque())
+    return dataLayout.getTypeSizeInBits(get(getContext()));
   return dataLayout.getTypeSizeInBits(get(getElementType()));
 }
 
 unsigned LLVMPointerType::getABIAlignment(const DataLayout &dataLayout,
                                           DataLayoutEntryListRef params) const {
   if (Optional<unsigned> alignment =
           getPointerDataLayoutEntry(params, *this, DLEntryPos::Abi))
     return *alignment;
 
+  if (isOpaque())
+    return dataLayout.getTypeABIAlignment(get(getContext()));
   return dataLayout.getTypeABIAlignment(get(getElementType()));
 }
 
 unsigned
 LLVMPointerType::getPreferredAlignment(const DataLayout &dataLayout,
                                        DataLayoutEntryListRef params) const {
   if (Optional<unsigned> alignment =
           getPointerDataLayoutEntry(params, *this, DLEntryPos::Preferred))
     return *alignment;
 
+  if (isOpaque())
+    return dataLayout.getTypePreferredAlignment(get(getContext()));
   return dataLayout.getTypePreferredAlignment(get(getElementType()));
 }
 
 bool LLVMPointerType::areCompatible(DataLayoutEntryListRef oldLayout,
                                     DataLayoutEntryListRef newLayout) const {
   for (DataLayoutEntryInterface newEntry : newLayout) {
     if (!newEntry.isTypeEntry())
       continue;

mlir/test/Dialect/LLVMIR/layout.mlir

func.func @no_spec() {
     // CHECK: preferred = 8
     // CHECK: size = 8
     "test.data_layout_query"() : () -> !llvm.ptr<i8, 3>
     // CHECK: alignment = 8
     // CHECK: bitsize = 64
     // CHECK: preferred = 8
     // CHECK: size = 8
     "test.data_layout_query"() : () -> !llvm.ptr<i8, 5>
+    // CHECK: alignment = 8
+  // CHECK: bitsize = 64
+    // CHECK: preferred = 8
+    // CHECK: size = 8
+    "test.data_layout_query"() : () -> !llvm.ptr<5>
     return
   }
 }
 
 // -----
 
 module attributes { dlti.dl_spec = #dlti.dl_spec<
   #dlti.dl_entry<!llvm.ptr<i8>, dense<[32, 32, 64]> : vector<3xi32>>,
func.func @spec() {
     // CHECK: preferred = 8
     // CHECK: size = 4
     "test.data_layout_query"() : () -> !llvm.ptr<i8, 3>
     // CHECK: alignment = 8
     // CHECK: bitsize = 64
     // CHECK: preferred = 8
     // CHECK: size = 8
     "test.data_layout_query"() : () -> !llvm.ptr<i8, 5>
+    // CHECK: alignment = 4
+  // CHECK: bitsize = 32
+    // CHECK: preferred = 8
+    // CHECK: size = 4
+    "test.data_layout_query"() : () -> !llvm.ptr<3>
     return
   }
 }
 
 // -----
 
 // expected-error@below {{unexpected layout attribute for pointer to 'i32'}}
 module attributes { dlti.dl_spec = #dlti.dl_spec<