On 09/29/2016 07:32 PM, Denys Vlasenko wrote:
+#ifdef SUBALIGN_LOG
We want to avoid adding new #defines; existing ones are being converted
to target hooks. I suspect the best way is to record whether an M value
was specified, and override it in the x86 option_override if required.
If that's infeasible for some reason we can revisit this.
+ /* Before -falign-foo=N,M,N2,M2 was introduced, x86 had a tweak.
+ -falign-functions=N with N > 8 was adding secondary alignment.
+ -falign-functions=10 was emitting this before every function:
+ .p2align 4,,9
+ .p2align 3
+ Now this behavior (and more) can be explicitly requested:
+ -falign-functions=16,10,8
+ Retain old behavior if N2 is missing: */
+ else if (a[0].log > SUBALIGN_LOG)
+ a[1].log = SUBALIGN_LOG;
So this would live in i386.c, probably.
Thanks, I'm working on it...
...and I can't find a sane way to achieve it in the way you prefer.
Hooking it into ix86_override_options_after_change()?
Like this?
/* Implement TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE hook. */
static void
ix86_override_options_after_change (void)
{
ix86_default_align (&global_options);
}
static void
ix86_default_align (struct gcc_options *opts)
{
struct align_flags *fa;
/* -falign-foo without argument: supply one */
if (opts->x_flag_align_functions && !opts->x_str_align_functions)
{
opts->x_str_align_functions =
processor_target_table[ix86_tune].align_func;
}
/* Before -falign-foo=N,M,N2,M2 was introduced, x86 had a tweak.
-falign-functions=N with N > 8 was adding secondary alignment.
-falign-functions=10 was emitting this before every function:
.p2align 4,,9
.p2align 3
Retain old behavior if N2 is missing: */
fa = this_target_flag_state->x_align_functions;
if (fa[1].log == 0 && fa[0].log > 3)
fa[1].log = 3;
}
Well, the problem here is that init_alignments() is called
much later than this hook. The
fa = this_target_flag_state->x_align_functions;
if (fa[1].log == 0 && fa[0].log > 3)
fa[1].log = 3;
will not trigger here: x_align_functions[0].log is not yet set!
Just set N2 to 2^3 unconditionally?
fa = this_target_flag_state->x_align_functions;
fa[1].log = 3;
This will make any alignment, even none: -falign-functions=1
have 8 byte subalign.
Help?
