Re: block_end_with_jump to a block question

[David Malcolm <dmalcolm@redhat.com>]

On Fri, 2023-06-16 at 16:56 +0000, Li, Yicheng via Jit wrote:
> Hi,
> 
> I created a a few blocks using gcc_jit_function_new_block.
> While I have a jit function param coming in as “index”.
> But the “index” has a type as gcc_jit_lvalue, which cannot be
> consider as an integer, thus, I cannot do
> gcc_jit_block_end_with_jump( block, NULL, elem_block[index].
> Is there a trick to do this?

Hi

It's not quite clear to me what the code is trying to do...

> 
> gcc_jit_lvalue *dst_input = gcc_jit_function_new_local( func, NULL, char_ptr_ptr_type, "dst_input" ),
> 
>                    *src_val = gcc_jit_function_new_local( func, NULL, char_ptr_type, "src_val" ),
> 
>                    *src_loop = gcc_jit_function_new_local( func, NULL, char_ptr_type, "src_loop" ),
> 
>                    *index_val = gcc_jit_function_new_local( func, NULL, int_ptr_type, "index_val" ),

...here you create a local variable called "index_val"...


> 
>                    *disp_val = gcc_jit_function_new_local( func, NULL, sizet_ptr_type, "disp_val" ),
> 
>                    *maxdata_val = gcc_jit_function_new_local( func, NULL, sizet_ptr_type, "maxdata_val" );
> 
> 
>     gcc_jit_block_add_assignment( block, NULL, dst_input, gcc_jit_param_as_rvalue( param[0] ) );
> 
>     gcc_jit_block_add_assignment( block, NULL, src_val, gcc_jit_param_as_rvalue( param[1] ) );
> 
>     gcc_jit_block_add_assignment( block, NULL, index_val, gcc_jit_param_as_rvalue( param[2] ) );

...and here you create an assignment equivalent to this C code:

   index_val = param[2];


> 
>     gcc_jit_block_add_assignment( block, NULL, disp_val, gcc_jit_param_as_rvalue( param[3] ) );
> 
>     gcc_jit_block_add_assignment( block, NULL, maxdata_val, gcc_jit_param_as_rvalue( param[4] ) );
> 
> 
>     gcc_jit_lvalue *dst_val = gcc_jit_context_new_array_access( ctxt, NULL, dst_input,
> 
>                                   gcc_jit_context_new_rvalue_from_int( ctxt, int_type, 0 ) ),
> 
>                    *index = gcc_jit_context_new_array_access( ctxt, NULL, index_val,
> 
>                                    gcc_jit_context_new_rvalue_from_int( ctxt, int_type, 0 ) ),

"index" here is an array access i.e. you're making an lvalue equivalent
to this C code:

  index_val[0]

which is equivalent to:


  *index_val


> 
>                    *disp = gcc_jit_context_new_array_access( ctxt, NULL, disp_val,
> 
>                                gcc_jit_context_new_rvalue_from_int( ctxt, int_type, 0 ) ),
> 
>                    *maxdata = gcc_jit_context_new_array_access( ctxt, NULL, maxdata_val,
> 
>                                   gcc_jit_context_new_rvalue_from_int( ctxt, int_type, 0 ) );
> 
> 
>     gcc_jit_lvalue *count_val = gcc_jit_function_new_local( func, NULL, int_type, "elem_count" );
> 
> 
>     gcc_jit_block *elem_block[desc_used],
> 
>                   *elem_exit_block[desc_used];
> 
>     int blockn = 0,
> 
>         nelem = 0;
> 
>     for( int i = 0; i <= desc_used; i++ ){
> 
>             char block_name[10];
> 
>             elem_block[nelem] = gcc_jit_function_new_block( func, itoa( blockn++, block_name, 10 ) );
> 
>             nelem++;
> 
>     }
> 
> 
>     gcc_jit_block_end_with_jump( block, NULL, elem_block[index] );

"index" here is the (gcc_jit_lvalue *) from above, referring to an
lvalue equivalent to "index_val[0]".

Which block do you want to be executed after "block"?  Or is this meant
to be a switch statement?  If so, look at
https://gcc.gnu.org/onlinedocs/jit/topics/functions.html#c.gcc_jit_block_end_with_switch

> 
> The error from compiler is
> 
> error: array subscript is not an integer
> 
>  1183 |     gcc_jit_block_end_with_jump( block, NULL,
> elem_block[index] );

This is looking up an element of the "elem_block" array, and so needs
an integer value, not a (gcc_jit_lvalue *).

Hope this is helpful
Dave