[LLVM-C] Add bindings to insert basic blocks

[CodaFi]

Summary

Now that we can create standalone basic blocks, it's useful to be able to append them. Add bindings to

• Insert a basic block after the current insertion block
• Append a basic block to the end of a function's list of basic blocks

[CodaFi]

@whitequark Could I get your sign off on this too?

[whitequark]

I think the names are confusing. Why not something like LLVMInsertExistingBasicBlock and LLVMAppendExistingBasicBlock?

[CodaFi]

In D59658#1456672, @whitequark wrote:

I think the names are confusing. Why not something like LLVMInsertExistingBasicBlock and LLVMAppendExistingBasicBlock?

Like to match LLVMInsertBasicBlock and LLVMAppendBasicBlock? The former's semantics don't really match its pair function. LLVMInsertBasicBlock is used to insert before another block where LLVMInsertBasicBlockAfterInsertBlock inserts at the current global insertion point. I agree with the LLVMAppendExistingBasicBlock name change.

[whitequark]

Agreed; I think it should still have Existing in the name if it takes a reference to a block, to distinguish from the existing set of (somewhat poorly named) functions.

[CodaFi]

A (verbose) compromise: LLVMInsertExistingBasicBlockAfterInsertBlock?

[whitequark]

Sure.

[whitequark]

LGTM

llvm/include/llvm-c/Core.h

  * Obtain the basic block that corresponds to the entry point of a
  * function.
  *
  * @see llvm::Function::getEntryBlock()
  */
 LLVMBasicBlockRef LLVMGetEntryBasicBlock(LLVMValueRef Fn);
 
 /**
+ * Insert the given basic block after the insertion point of the given builder.
+ *
+ * The insertion point must be valid.
+ *
+ * @see llvm::Function::BasicBlockListType::insertAfter()
+ */
+void LLVMInsertExistingBasicBlockAfterInsertBlock(LLVMBuilderRef Builder,
+                                                  LLVMBasicBlockRef BB);
+
+/**
+ * Append the given basic block to the basic block list of the given function.
+ *
+ * @see llvm::Function::BasicBlockListType::push_back()
+ */
+void LLVMAppendExistingBasicBlock(LLVMValueRef Fn,
+                                  LLVMBasicBlockRef BB);
+  
+/**
  * Create a new basic block without inserting it into a function.
  *
  * @see llvm::BasicBlock::Create()
  */
 LLVMBasicBlockRef LLVMCreateBasicBlockInContext(LLVMContextRef C,
                                                 const char *Name);
 
 /**

llvm/lib/IR/Core.cpp

LLVMBasicBlockRef LLVMGetPreviousBasicBlock(LLVMBasicBlockRef BB) {
   return wrap(&*--I);
 }
 
 LLVMBasicBlockRef LLVMCreateBasicBlockInContext(LLVMContextRef C,
                                                 const char *Name) {
   return wrap(llvm::BasicBlock::Create(*unwrap(C), Name));
 }
 
+void LLVMInsertExistingBasicBlockAfterInsertBlock(LLVMBuilderRef Builder,
+                                                  LLVMBasicBlockRef BB) {
+  BasicBlock *ToInsert = unwrap(BB);
+  BasicBlock *CurBB = unwrap(Builder)->GetInsertBlock();
+  assert(CurBB && "current insertion point is invalid!");
+  CurBB->getParent()->getBasicBlockList().insertAfter(CurBB->getIterator(),
+                                                      ToInsert);
+}
+
+void LLVMAppendExistingBasicBlock(LLVMValueRef Fn,
+                                  LLVMBasicBlockRef BB) {
+  unwrap<Function>(Fn)->getBasicBlockList().push_back(unwrap(BB));
+}
+
 LLVMBasicBlockRef LLVMAppendBasicBlockInContext(LLVMContextRef C,
                                                 LLVMValueRef FnRef,
                                                 const char *Name) {
   return wrap(BasicBlock::Create(*unwrap(C), Name, unwrap<Function>(FnRef)));
 }
 
 LLVMBasicBlockRef LLVMAppendBasicBlock(LLVMValueRef FnRef, const char *Name) {
   return LLVMAppendBasicBlockInContext(LLVMGetGlobalContext(), FnRef, Name);