Drop the JointMatrixINTEL struct-renaming pass when opaque pointers are enabled. (#1570)

The frontend is being changed to lower the struct name to the correct LLVM name
directly, obviating the need for this check. See
#6535 for this change.

This marks the removal of the final call to the deprecated method
Type::getPointerElementType, although there remains some code that is not fully
working with opaque pointers enabled.

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@e2bb479

Author: jcranmer-intel

llvm-spirv/lib/SPIRV/SPIRVRegularizeLLVM.cpp

@@ -354,6 +354,10 @@ void SPIRVRegularizeLLVMBase::adaptStructTypes(StructType *ST) {
   STName.consume_front("__spv::");
   StringRef MangledName = STName.substr(0, STName.find('.'));
 
+  // Older versions of clang will generate JointMatrixINTEL types using this
+  // representation. Newer versions will generate the correct struct name
+  // "%spirv.JointMatrixINTEL._{parameters}" directly, obviating the need for
+  // this check.
   // Representation in LLVM IR before the translator is a pointer array wrapped
   // in a structure:
   // %struct.__spirv_JointMatrixINTEL = type { [R x [C x [L x [S x type]]]]* }
@@ -370,12 +374,13 @@ void SPIRVRegularizeLLVMBase::adaptStructTypes(StructType *ST) {
   // register by OpCompositeConstruct. And we can't claim, that the Result type
   // of OpCompositeConstruct instruction is always the joint matrix type, it's
   // simply not true.
-  if (MangledName == "__spirv_JointMatrixINTEL") {
+  if (MangledName == "__spirv_JointMatrixINTEL" && !ST->isOpaquePointerTy()) {
     auto *PtrTy = dyn_cast<PointerType>(ST->getElementType(0));
     assert(PtrTy &&
            "Expected a pointer to an array to represent joint matrix type");
     std::vector<size_t> TypeLayout;
-    ArrayType *ArrayTy = dyn_cast<ArrayType>(PtrTy->getPointerElementType());
+    ArrayType *ArrayTy =
+        dyn_cast<ArrayType>(PtrTy->getNonOpaquePointerElementType());
     assert(ArrayTy && "Expected a pointer element type of an array type to "
                       "represent joint matrix type");
     TypeLayout.push_back(ArrayTy->getNumElements());