Update doc with llvm coro hello world

Author: GorNishanov

docs/Coroutines.md

@@ -49,4 +49,63 @@ def int_experimental_coro_from_promise : Intrinsic<[llvm_ptr_ty], [llvm_anyptr_t
 def int_experimental_coro_elide : Intrinsic<[llvm_ptr_ty], [], []>;
 def int_experimental_coro_delete : Intrinsic<[llvm_i1_ty], [llvm_ptr_ty], []>;
 
-## Optimizations
+## Optimizations
+
+## Coroutine Hello World
+
+declare noalias i8* @malloc(i32)
+declare void @free(i8*)
+declare void @yield(i32)
+
+declare void @llvm.experimental.coro.resume(i8*)
+declare void @llvm.experimental.coro.destroy(i8*)
+declare i8* @llvm.experimental.coro.init(i8*, i8*, i8*)
+declare i32 @llvm.experimental.coro.size()
+declare i1 @llvm.experimental.coro.fork()
+declare token @llvm.experimental.coro.save(i32)
+;declare i8* @llvm.experimental.coro.frame()
+declare i1 @llvm.experimental.coro.suspend(token)
+declare i8* @llvm.experimental.coro.delete(i8*)
+declare void @llvm.experimental.coro.resume.end()
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+define i8* @f(i32 %n) {
+entry:
+ %frame.size = call i32 @llvm.experimental.coro.size()
+ %alloc = call noalias i8* @malloc(i32 %frame.size)
+ %frame = call i8* @llvm.experimental.coro.init(i8* %alloc, i8* null, i8* null)
+ %first.return = call i1 @llvm.experimental.coro.fork()
+ br i1 %first.return, label %coro.return, label %coro.start
+
+coro.start:
+ %n.val = phi i32 [ %n, %entry ], [ %inc, %resume ]
+ call void @yield(i32 %n.val)
+ %save = call token @llvm.experimental.coro.save(i32 1)
+ %suspend = call i1 @llvm.experimental.coro.suspend(token %save)
+ br i1 %suspend, label %resume, label %cleanup
+
+resume:
+ %inc = add i32 %n.val, 1
+ br label %coro.start
+
+cleanup:
+ %mem = call i8* @llvm.experimental.coro.delete(i8* %frame)
+ call void @free(i8* %mem)
+ call void @llvm.experimental.coro.resume.end() 
+ br label %coro.return
+
+coro.return:
+ ret i8* %frame
+}
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+define i32 @main() {
+entry:
+ %hdl = call i8* @f(i32 4)
+ call void @llvm.experimental.coro.resume(i8* %hdl)
+ call void @llvm.experimental.coro.resume(i8* %hdl)
+ call void @llvm.experimental.coro.destroy(i8* %hdl)
+ ret i32 0
+}