Add a method to get element at in a struct from the C API

[deadalnix]

Summary

As per title. It is kind of retarged to have to allocate an array to get all the type when one is only interested in one.

[dblaikie]

Best to delete this review and create a new one, ensuring that one of the
community mailing lists is included in the review from the start.

Unfortunately once you create a review - there's no way to get phab to
re-send this initial email after you add the list :/

[deadalnix]

D10148

include/llvm-c/Core.h

  * invocation, this array will be populated with the structure's
  * elements. The objects in the destination array will have a lifetime
  * of the structure type itself, which is the lifetime of the context it
  * is contained in.
  */
 void LLVMGetStructElementTypes(LLVMTypeRef StructTy, LLVMTypeRef *Dest);
 
 /**
+ * Get the type of the element at a given index in the structure.
+ *
+ * @see llvm::StructType::getTypeAtIndex()
+ */
+LLVMTypeRef LLVMStructGetTypeAtIndex(LLVMTypeRef StructTy, unsigned i);
+
+/**
  * Determine whether a structure is packed.
  *
  * @see llvm::StructType::isPacked()
  */
 LLVMBool LLVMIsPackedStruct(LLVMTypeRef StructTy);
 
 /**
  * Determine whether a structure is opaque.

lib/IR/Core.cpp

 
 void LLVMGetStructElementTypes(LLVMTypeRef StructTy, LLVMTypeRef *Dest) {
   StructType *Ty = unwrap<StructType>(StructTy);
   for (StructType::element_iterator I = Ty->element_begin(),
                                     E = Ty->element_end(); I != E; ++I)
     *Dest++ = wrap(*I);
 }
 
+LLVMTypeRef LLVMStructGetTypeAtIndex(LLVMTypeRef StructTy, unsigned i) {
+  StructType *Ty = unwrap<StructType>(StructTy);
+  return wrap(Ty->getTypeAtIndex(i));
+}
+
 LLVMBool LLVMIsPackedStruct(LLVMTypeRef StructTy) {
   return unwrap<StructType>(StructTy)->isPacked();
 }
 
 LLVMBool LLVMIsOpaqueStruct(LLVMTypeRef StructTy) {
   return unwrap<StructType>(StructTy)->isOpaque();
 }