On Fri, May 06, 2016 at 04:00:28PM +0100, Jiong Wang wrote:
> This patch fixes PR63596.
>
> There is no need to push/pop all arguments registers. We only need to
> push and pop those registers used. These use info is calculated by a
> dedicated vaarg optimization tree pass "tree-stdarg", the backend should
> honor it's analysis result.
>
> For a simple testcase where vaarg declared but actually not used:
>
> int
> f (int a, ...)
> {
> return a;
> }
>
> before this patch, we are generating:
>
> f:
> sub sp, sp, #192
> stp x1, x2, [sp, 136]
> stp x3, x4, [sp, 152]
> stp x5, x6, [sp, 168]
> str x7, [sp, 184]
> str q0, [sp]
> str q1, [sp, 16]
> str q2, [sp, 32]
> str q3, [sp, 48]
> str q4, [sp, 64]
> str q5, [sp, 80]
> str q6, [sp, 96]
> str q7, [sp, 112]
> add sp, sp, 192
> ret
>
> after this patch, it's optimized into:
>
> f:
> ret
Can't argue with that! Nice!
> OK for trunk?
OK.
Thanks,
James
