[PATCH v3] LangRef: modify varargs example to include x86_64

[Ramkumar Ramachandra]

Sorry about that typo in the address of llvm-commits.

On Sat, Nov 1, 2014 at 8:59 PM, Ramkumar Ramachandra <artagnon at gmail.com> wrote:
> va_list is a different type than the generic i8* on x86_64. Include this
> type in a comment so that users can graft it in with minimal
> effort.
>
> Cc: Reid Kleckner <rnk at google.com>
> Cc: Tim Northover <t.p.northover at gmail.com>
> Signed-off-by: Ramkumar Ramachandra <artagnon at gmail.com>
> ---
>  docs/LangRef.rst | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/docs/LangRef.rst b/docs/LangRef.rst
> index ddef803..3b7d80b 100644
> --- a/docs/LangRef.rst
> +++ b/docs/LangRef.rst
> @@ -6884,14 +6884,21 @@ variable argument handling intrinsic functions are used.
>
>  .. code-block:: llvm
>
> +    ; This struct is different for every platform. For most platforms,
> +    ; it is merely an i8*.
> +    %struct.va_list = type { i8* }
> +
> +    ; For Unix x86_64 platforms, va_list is the following struct:
> +    ; %struct.va_list = type { i32, i32, i8*, i8* }
> +
>      define i32 @test(i32 %X, ...) {
>        ; Initialize variable argument processing
> -      %ap = alloca i8*
> -      %ap2 = bitcast i8** %ap to i8*
> +      %ap = alloca %struct.va_list
> +      %ap2 = bitcast %struct.va_list* %ap to i8*
>        call void @llvm.va_start(i8* %ap2)
>
>        ; Read a single integer argument
> -      %tmp = va_arg i8** %ap, i32
> +      %tmp = va_arg i8* %ap2, i32
>
>        ; Demonstrate usage of llvm.va_copy and llvm.va_end
>        %aq = alloca i8*
> --
> 2.1.3
>