[llvm-c] Add LLVMSetTailCallKind and LLVMGetTailCallKind

[yamt]

add a test

[yamt]

i added a few people who have reviewed nearby files recently to reviewers. i hope it's ok.

[aeubanks]

lgtm aside from some nits

can you add this to the release notes?

llvm/include/llvm-c/Core.h

472

can you add @see CallInst::TailCallKind?

llvm/test/Bindings/llvm-c/echo.ll

106

can you also add a notail test?

[yamt]

test, comment, release notes

[aeubanks]

lgtm with wording changes

llvm/docs/ReleaseNotes.rst

119

I'd reword this to be

Added ``LLVMGetTailCallKind`` and ``LLVMSetTailCallKind`` to
allow getting and setting ``tail``, ``musttail``, and ``notail``
attributes on call instructions.

[yamt]

release notes rewording

[yamt]

is there anything holding this back?

[aeubanks]

it's good to land, did you need me to land it for you?

[yamt]

In D153107#4539047, @aeubanks wrote:

it's good to land, did you need me to land it for you?

yes.
i don't have any permissions here.

llvm/docs/ReleaseNotes.rst

 ------------------------------
 
 * The python bindings have been removed.
 
 
 Changes to the C API
 --------------------
 
+* Added ``LLVMGetTailCallKind`` and ``LLVMSetTailCallKind`` to
+  allow getting and setting ``tail``, ``musttail``, and ``notail``
+  attributes on call instructions.
+
 Changes to the CodeGen infrastructure
 -------------------------------------
 
 Changes to the Metadata Info
 ---------------------------------
 
 Changes to the Debug Info
 ---------------------------------

llvm/include/llvm-c/Core.h

 enum {
   LLVMAttributeReturnIndex = 0U,
   // ISO C restricts enumerator values to range of 'int'
   // (4294967295 is too large)
   // LLVMAttributeFunctionIndex = ~0U,
   LLVMAttributeFunctionIndex = -1,
 };
 
+/**
+ * Tail call kind for LLVMSetTailCallKind and LLVMGetTailCallKind.
+ *
+ * Note that 'musttail' implies 'tail'.
+ *
+ * @see CallInst::TailCallKind
+ */
+typedef enum {
+  LLVMTailCallKindNone = 0,
+  LLVMTailCallKindTail = 1,
+  LLVMTailCallKindMustTail = 2,
+  LLVMTailCallKindNoTail = 3,
+} LLVMTailCallKind;
+
 typedef unsigned LLVMAttributeIndex;
 
 /**
  * @}
  */
 
 /** Deallocate and destroy all ManagedStatic variables.
     @see llvm::llvm_shutdown

  *
  * This only works on llvm::CallInst instructions.
  *
  * @see llvm::CallInst::setTailCall()
  */
 void LLVMSetTailCall(LLVMValueRef CallInst, LLVMBool IsTailCall);
 
 /**
+ * Obtain a tail call kind of the call instruction.
+ *
+ * @see llvm::CallInst::setTailCallKind()
+ */
+LLVMTailCallKind LLVMGetTailCallKind(LLVMValueRef CallInst);
+
+/**
+ * Set the call kind of the call instruction.
+ *
+ * @see llvm::CallInst::getTailCallKind()
+ */
+void LLVMSetTailCallKind(LLVMValueRef CallInst, LLVMTailCallKind kind);
+
+/**
  * Return the normal destination basic block.
  *
  * This only works on llvm::InvokeInst instructions.
  *
  * @see llvm::InvokeInst::getNormalDest()
  */
 LLVMBasicBlockRef LLVMGetNormalDest(LLVMValueRef InvokeInst);
 

llvm/lib/IR/Core.cpp

 LLVMBool LLVMIsTailCall(LLVMValueRef Call) {
   return unwrap<CallInst>(Call)->isTailCall();
 }
 
 void LLVMSetTailCall(LLVMValueRef Call, LLVMBool isTailCall) {
   unwrap<CallInst>(Call)->setTailCall(isTailCall);
 }
 
+LLVMTailCallKind LLVMGetTailCallKind(LLVMValueRef Call) {
+  return (LLVMTailCallKind)unwrap<CallInst>(Call)->getTailCallKind();
+}
+
+void LLVMSetTailCallKind(LLVMValueRef Call, LLVMTailCallKind kind) {
+  unwrap<CallInst>(Call)->setTailCallKind((CallInst::TailCallKind)kind);
+}
+
 /*--.. Operations on invoke instructions (only) ............................--*/
 
 LLVMBasicBlockRef LLVMGetNormalDest(LLVMValueRef Invoke) {
   return wrap(unwrap<InvokeInst>(Invoke)->getNormalDest());
 }
 
 LLVMBasicBlockRef LLVMGetUnwindDest(LLVMValueRef Invoke) {
   if (CleanupReturnInst *CRI = dyn_cast<CleanupReturnInst>(unwrap(Invoke))) {

llvm/test/Bindings/llvm-c/echo.ll

define i32 @iops(i32 %a, i32 %b) {
   ret i32 %23
 }
 
 define i32 @call() {
   %1 = call i32 @iops(i32 23, i32 19)
   ret i32 %1
 }
 
+define i32 @tailcall() {
+  %1 = tail call i32 @call()
+  ret i32 %1
+}
+
+define i32 @musttailcall() {
+  %1 = musttail call i32 @call()
+  ret i32 %1
+}
+
+define i32 @notailcall() {
+  %1 = notail call i32 @call()
+  ret i32 %1
+}
+
 define i32 @cond(i32 %a, i32 %b) {
   br label %br
 unreachable:
   unreachable
 br:
   %1 = icmp eq i32 %a, %b
   br i1 %1, label %next0, label %unreachable
 next0:

llvm/tools/llvm-c-test/echo.cpp

switch(Op) {
       case LLVMCall: {
         SmallVector<LLVMValueRef, 8> Args;
         int ArgCount = LLVMGetNumArgOperands(Src);
         for (int i = 0; i < ArgCount; i++)
           Args.push_back(CloneValue(LLVMGetOperand(Src, i)));
         LLVMTypeRef FnTy = CloneType(LLVMGetCalledFunctionType(Src));
         LLVMValueRef Fn = CloneValue(LLVMGetCalledValue(Src));
         Dst = LLVMBuildCall2(Builder, FnTy, Fn, Args.data(), ArgCount, Name);
-        LLVMSetTailCall(Dst, LLVMIsTailCall(Src));
+        LLVMSetTailCallKind(Dst, LLVMGetTailCallKind(Src));
         CloneAttrs(Src, Dst);
         break;
       }
       case LLVMResume: {
         Dst = LLVMBuildResume(Builder, CloneValue(LLVMGetOperand(Src, 0)));
         break;
       }
       case LLVMLandingPad: {