On Tue, Jun 23, 2015 at 09:18:52AM +0100, James Greenhalgh wrote:
> This patch fixes the issue by always calling get_move_ratio in the SRA
> code, ensuring that an up-to-date value is used.
>
> Unfortunately, this means we have to use 0 as a sentinel value for
> the parameter - indicating no user override of the feature - and
> therefore cannot use it to disable scalarization. However, there
> are other ways to disable scalarazation (-fno-tree-sra) so this is not
> a great loss.
You can handle even that.
> diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
> index 8e34244..e2419af 100644
> --- a/gcc/tree-sra.c
> +++ b/gcc/tree-sra.c
> @@ -2549,12 +2549,24 @@ analyze_all_variable_accesses (void)
> bitmap tmp = BITMAP_ALLOC (NULL);
> bitmap_iterator bi;
> unsigned i;
> + bool optimize_speed_p = !optimize_function_for_size_p (cfun);
> +
> unsigned max_scalarization_size
> - = (optimize_function_for_size_p (cfun)
> - ? PARAM_VALUE (PARAM_SRA_MAX_SCALARIZATION_SIZE_SIZE)
> - : PARAM_VALUE (PARAM_SRA_MAX_SCALARIZATION_SIZE_SPEED))
> + = (optimize_speed_p
> + ? PARAM_VALUE (PARAM_SRA_MAX_SCALARIZATION_SIZE_SPEED)
> + : PARAM_VALUE (PARAM_SRA_MAX_SCALARIZATION_SIZE_SIZE))
> * BITS_PER_UNIT;
>
> + /* If the user didn't set PARAM_SRA_MAX_SCALARIZATION_SIZE_<...>,
> + fall back to a target default. This means that zero cannot be
> + used to disable scalarization as we've taken it as a sentinel
> + value. This is not ideal, but see PR66119 for the reason we
> + can't simply set the target defaults ahead of time during option
> + handling. */
> + if (!max_scalarization_size)
enum compiler_param param
= optimize_function_for_size_p (cfun)
? PARAM_SRA_MAX_SCALARIZATION_SIZE_SIZE
: PARAM_SRA_MAX_SCALARIZATION_SIZE_SPEED;
unsigned max_scalarization_size = PARAM_VALUE (param) * BITS_PER_UNIT;
if (!max_scalarization_size && !global_options_set.x_param_values[param])
Then it will handle explicit --param sra-max-scalarization-size-Os*=0
differently from implicit 0.
Or you could allow value of -1 for those params and make that the default
- -1 would mean the special get_move_ration value, 0 would disable, > 0
would be the requested scalarization.
OT, shouldn't max_scalarization_size be at least unsigned HOST_WIDE_INT,
so that it doesn't overflow for larger values (0x40000000 etc.)?
Probably need some cast in the multiplication to avoid UB in the compiler.
Jakub
