[llvm-c] Remove pointee support from LLVMGetElementType

[nikic]

I think it's too early to drop the LLVMPointerType functions. These are useful for frontends that still support LLVM 14 and for that reason still generate typed IR (which is automatically converted to opaque IR). For rustc the need for this will go away in about 6 months.

Of course it's possible for the frontend to call one or the other depending on version, but I don't think there's any benefit to that at this point.

[aeubanks]

my motivation for this is to prevent people from being able to add code to our repo that relies on typed pointers. just removing LLVMPointerTypeIsOpaque and the pointer branch in LLVMGetElementType should achieve that, does that sound ok?

[nikic]

In D145717#4182480, @aeubanks wrote:

my motivation for this is to prevent people from being able to add code to our repo that relies on typed pointers. just removing LLVMPointerTypeIsOpaque and the pointer branch in LLVMGetElementType should achieve that, does that sound ok?

That would be fine I think. Though possible just dropping the branch from LLVMGetElementType is enough?

[aeubanks]

only touch LLVMGetElementType

[nikic]

LG

llvm/docs/ReleaseNotes.rst

 --------------------
 
 * ``LLVMContextSetOpaquePointers``, a temporary API to pin to legacy typed
   pointer, has been removed.
 * Functions for adding legacy passes like ``LLVMAddInstructionCombiningPass``
   have been removed.
 * Removed ``LLVMPassManagerBuilderRef`` and functions interacting with it.
   These belonged to the no longer supported legacy pass manager.
+* As part of the opaque pointer transition, ``LLVMGetElementType`` no longer
+  gives the pointee type of a pointer type.
 
 Changes to the FastISel infrastructure
 --------------------------------------
 
 * ...
 
 Changes to the DAG infrastructure
 ---------------------------------

llvm/include/llvm-c/Core.h

  * for array, vector, and pointer types.
  *
  * @{
  */
 
 /**
  * Obtain the element type of an array or vector type.
  *
- * This currently also works for pointer types, but this usage is deprecated.
- *
  * @see llvm::SequentialType::getElementType()
  */
 LLVMTypeRef LLVMGetElementType(LLVMTypeRef Ty);
 
 /**
  * Returns type's subtypes
  *
  * @see llvm::Type::subtypes()

llvm/lib/IR/Core.cpp

 
 LLVMTypeRef LLVMScalableVectorType(LLVMTypeRef ElementType,
                                    unsigned ElementCount) {
   return wrap(ScalableVectorType::get(unwrap(ElementType), ElementCount));
 }
 
 LLVMTypeRef LLVMGetElementType(LLVMTypeRef WrappedTy) {
   auto *Ty = unwrap(WrappedTy);
-  if (auto *PTy = dyn_cast<PointerType>(Ty))
-    return wrap(PTy->getNonOpaquePointerElementType());
   if (auto *ATy = dyn_cast<ArrayType>(Ty))
     return wrap(ATy->getElementType());
   return wrap(cast<VectorType>(Ty)->getElementType());
 }
 
 unsigned LLVMGetNumContainedTypes(LLVMTypeRef Tp) {
     return unwrap(Tp)->getNumContainedTypes();
 }