[LLVMdev] RFC: llvm-convert.cpp Patch

[Dale Johannesen]

On Nov 6, 2007, at 5:45 PM, Bill Wendling wrote:
> $ more testcase.c.t03.generic
> Qux ()
> {
>   static char C.0[11] = {0};
>   char Bar[11];
>
>   Bar = C.0;
> }
>
> Anyway, it turns out that the gimplifier was generating the correct
> alignment, but it was being overridden in assemble_variable():
>
>   /* On some machines, it is good to increase alignment sometimes.  */
>   if (! DECL_USER_ALIGN (decl))
>     {
> #ifdef DATA_ALIGNMENT
>       align = DATA_ALIGNMENT (TREE_TYPE (decl), align);
> #endif
> #ifdef CONSTANT_ALIGNMENT
> =>    if (DECL_INITIAL (decl) != 0 && DECL_INITIAL (decl) !=  
> error_mark_node)
>         align = CONSTANT_ALIGNMENT (DECL_INITIAL (decl), align);
> #endif
>     }

Not sure I'm getting it, is this Bar itself or the constructed C.0  
that's getting realigned?

> By setting the DECL_USER_ALIGN field, we can get the correct  
> alignment.
>
> Comments?
>
> -bw
>
> Index: gimplify.c
> ===================================================================
> --- gimplify.c  (revision 43658)
> +++ gimplify.c  (working copy)
> @@ -2756,7 +2756,8 @@
>                 TREE_STATIC (new) = 1;
>                 TREE_READONLY (new) = 1;
>                 DECL_INITIAL (new) = ctor;
> -               if (align > DECL_ALIGN (new))
> +               /* LLVM LOCAL - Set DECL_USER_ALIGN when equal */
> +               if (align >= DECL_ALIGN (new))
>                   {
>                     DECL_ALIGN (new) = align;
>                     DECL_USER_ALIGN (new) = 1;
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