[coroutines] Add syntax coloring to examples in Coroutines.rst

docs/Coroutines.rst

 
 This coroutine calls some function `print` with value `n` as an argument and
 suspends execution. Every time this coroutine resumes, it calls `print` again with an argument one bigger than the last time. This coroutine never completes by itself and must be destroyed explicitly. If we use this coroutine with 
 a `main` shown in the previous section. It will call `print` with values 4, 5 
 and 6 after which the coroutine will be destroyed.
 
 The LLVM IR for this coroutine looks like this:
 
-.. code-block:: none
+.. code-block:: llvm
 
   define i8* @f(i32 %n) {
   entry:
     %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
     %size = call i32 @llvm.coro.size.i32()
     %alloc = call i8* @malloc(i32 %size)
     %hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %alloc)
     br label %loop

 allocated in the coroutine frame and `%n.val` is spilled and reloaded from that
 slot as needed.
 
 We also store addresses of the resume and destroy functions so that the 
 `coro.resume` and `coro.destroy` intrinsics can resume and destroy the coroutine
 when its identity cannot be determined statically at compile time. For our 
 example, the coroutine frame will be:
 
-.. code-block:: text
+.. code-block:: llvm
 
   %f.frame = type { void (%f.frame*)*, void (%f.frame*)*, i32 }
 
 After resume and destroy parts are outlined, function `f` will contain only the 
 code responsible for creation and initialization of the coroutine frame and 
 execution of the coroutine until a suspend point is reached:
 
-.. code-block:: none
+.. code-block:: llvm
 
   define i8* @f(i32 %n) {
   entry:
     %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
     %alloc = call noalias i8* @malloc(i32 24)
     %0 = call noalias i8* @llvm.coro.begin(token %id, i8* %alloc)
     %frame = bitcast i8* %0 to %f.frame*
     %1 = getelementptr %f.frame, %f.frame* %frame, i32 0, i32 0

 RAII idiom and is suitable for allocation elision optimization which avoid 
 dynamic allocation by storing the coroutine frame as a static `alloca` in its 
 caller.
 
 In the entry block, we will call `coro.alloc`_ intrinsic that will return `true`
 when dynamic allocation is required, and `false` if dynamic allocation is 
 elided.
 
-.. code-block:: none
+.. code-block:: llvm
 
   entry:
     %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
     %need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
     br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin
   dyn.alloc:
     %size = call i32 @llvm.coro.size.i32()
     %alloc = call i8* @CustomAlloc(i32 %size)
     br label %coro.begin
   coro.begin:
     %phi = phi i8* [ null, %entry ], [ %alloc, %dyn.alloc ]
     %hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %phi)
 
 In the cleanup block, we will make freeing the coroutine frame conditional on
 `coro.free`_ intrinsic. If allocation is elided, `coro.free`_ returns `null`
 thus skipping the deallocation code:
 
-.. code-block:: text
+.. code-block:: llvm
 
   cleanup:
     %mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
     %need.dyn.free = icmp ne i8* %mem, null
     br i1 %need.dyn.free, label %dyn.free, label %if.end
   dyn.free:
     call void @CustomFree(i8* %mem)
     br label %if.end
for(;;) {
        print(-n);
        <suspend>
      }
   }
 
 Matching LLVM code would look like (with the rest of the code remaining the same
 as the code in the previous section):
 
-.. code-block:: text
+.. code-block:: llvm
 
   loop:
     %n.addr = phi i32 [ %n, %entry ], [ %inc, %loop.resume ]
     call void @print(i32 %n.addr) #4
     %2 = call i8 @llvm.coro.suspend(token none, i1 false)
     switch i8 %2, label %suspend [i8 0, label %loop.resume
                                   i8 1, label %cleanup]
   loop.resume:
.. code-block:: text
   }
 
 In this case, coroutine should be ready for resumption prior to a call to 
 `async_op1` and `async_op2`. The `coro.save`_ intrinsic is used to indicate a
 point when coroutine should be ready for resumption (namely, when a resume index
 should be stored in the coroutine frame, so that it can be resumed at the 
 correct resume point):
 
-.. code-block:: text
+.. code-block:: llvm
 
   if.true:
     %save1 = call token @llvm.coro.save(i8* %hdl)
-    call void async_op1(i8* %hdl)
+    call void @async_op1(i8* %hdl)
     %suspend1 = call i1 @llvm.coro.suspend(token %save1, i1 false)
     switch i8 %suspend1, label %suspend [i8 0, label %resume1
                                          i8 1, label %cleanup]
   if.false:
     %save2 = call token @llvm.coro.save(i8* %hdl)
-    call void async_op2(i8* %hdl)
+    call void @async_op2(i8* %hdl)
     %suspend2 = call i1 @llvm.coro.suspend(token %save2, i1 false)
     switch i8 %suspend1, label %suspend [i8 0, label %resume2
                                          i8 1, label %cleanup]
 
 .. _coroutine promise:
 
 Coroutine Promise
 -----------------
 
 A coroutine author or a frontend may designate a distinguished `alloca` that can
 be used to communicate with the coroutine. This distinguished alloca is called
 **coroutine promise** and is provided as the second parameter to the 
 `coro.id`_ intrinsic.
 
 The following coroutine designates a 32 bit integer `promise` and uses it to
 store the current value produced by a coroutine.
 
-.. code-block:: text
+.. code-block:: llvm
 
   define i8* @f(i32 %n) {
   entry:
     %promise = alloca i32
     %pv = bitcast i32* %promise to i8*
     %id = call token @llvm.coro.id(i32 0, i8* %pv, i8* null, i8* null)
     %need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
     br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin

 Using this intrinsic on a coroutine that does not have a coroutine promise
 leads to undefined behavior. It is possible to read and modify coroutine
 promise of the coroutine which is currently executing. The coroutine author and
 a coroutine user are responsible to makes sure there is no data races.
 
 Example:
 """"""""
 
-.. code-block:: text
+.. code-block:: llvm
 
   define i8* @f(i32 %n) {
   entry:
     %promise = alloca i32
     %pv = bitcast i32* %promise to i8*
     ; the second argument to coro.id points to the coroutine promise.
     %id = call token @llvm.coro.id(i32 0, i8* %pv, i8* null, i8* null)
     ...

 identifying the coroutine.
 
 The second argument is a pointer to the coroutine frame. This should be the same
 pointer that was returned by prior `coro.begin` call.
 
 Example (custom deallocation function):
 """""""""""""""""""""""""""""""""""""""
 
-.. code-block:: text
+.. code-block:: llvm
 
   cleanup:
     %mem = call i8* @llvm.coro.free(token %id, i8* %frame)
     %mem_not_null = icmp ne i8* %mem, null
     br i1 %mem_not_null, label %if.then, label %if.end
   if.then:
     call void @CustomFree(i8* %mem)
     br label %if.end
   if.end:
     ret void
 
 Example (standard deallocation functions):
 """"""""""""""""""""""""""""""""""""""""""
 
-.. code-block:: text
+.. code-block:: llvm
 
   cleanup:
     %mem = call i8* @llvm.coro.free(token %id, i8* %frame)
     call void @free(i8* %mem)
     ret void
 
 .. _coro.alloc:
 

 
 A frontend should emit at most one `coro.alloc` intrinsic per coroutine.
 The intrinsic is used to suppress dynamic allocation of the coroutine frame
 when possible.
 
 Example:
 """"""""
 
-.. code-block:: text
+.. code-block:: llvm
 
   entry:
     %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
     %dyn.alloc.required = call i1 @llvm.coro.alloc(token %id)
     br i1 %dyn.alloc.required, label %coro.alloc, label %coro.begin
 
   coro.alloc:
     %frame.size = call i32 @llvm.coro.size()

 The `CoroSpit` pass replaces `coro.end` with ``True`` in the resume functions,
 thus leading to immediate unwind to the caller, whereas in start function it
 is replaced with ``False``, thus allowing to proceed to the rest of the cleanup
 code that is only needed during initial invocation of the coroutine.
 
 For Windows Exception handling model, a frontend should attach a funclet bundle
 referring to an enclosing cleanuppad as follows:
 
-.. code-block:: text
+.. code-block:: llvm
 
     ehcleanup: 
       %tok = cleanuppad within none []
       %unused = call i1 @llvm.coro.end(i8* null, i1 true) [ "funclet"(token %tok) ]
       cleanupret from %tok unwind label %RestOfTheCleanup
 
 The `CoroSplit` pass, if the funclet bundle is present, will insert 
 ``cleanupret from %tok unwind to caller`` before

 The second argument indicates whether this suspension point is `final`_.
 The second argument only accepts constants. If more than one suspend point is
 designated as final, the resume and destroy branches should lead to the same
 basic blocks.
 
 Example (normal suspend point):
 """""""""""""""""""""""""""""""
 
-.. code-block:: text
+.. code-block:: llvm
 
     %0 = call i8 @llvm.coro.suspend(token none, i1 false)
     switch i8 %0, label %suspend [i8 0, label %resume
                                   i8 1, label %cleanup]
 
 Example (final suspend point):
 """"""""""""""""""""""""""""""
 
-.. code-block:: text
+.. code-block:: llvm
 
   while.end:
     %s.final = call i8 @llvm.coro.suspend(token none, i1 true)
     switch i8 %s.final, label %suspend [i8 0, label %trap
                                         i8 1, label %cleanup]
   trap: 
     call void @llvm.trap()
     unreachable

 represent an asynchronous control flow driven by callbacks representing
 completions of asynchronous operations.
 
 In such a case, a coroutine should be ready for resumption prior to a call to 
 `async_op` function that may trigger resumption of a coroutine from the same or
 a different thread possibly prior to `async_op` call returning control back
 to the coroutine:
 
-.. code-block:: text
+.. code-block:: llvm
 
     %save1 = call token @llvm.coro.save(i8* %hdl)
-    call void async_op1(i8* %hdl)
+    call void @async_op1(i8* %hdl)
     %suspend1 = call i1 @llvm.coro.suspend(token %save1, i1 false)
     switch i8 %suspend1, label %suspend [i8 0, label %resume1
                                          i8 1, label %cleanup]
 
 .. _coro.param:
 
 'llvm.coro.param' Intrinsic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^