On Tue, Oct 19, 2021 at 01:08:30PM +0530, Siddhesh Poyarekar wrote:
> Compute the unknown size value as a function of the min/max bit of
> object_size_type. This transforms into a neat little branchless
> sequence on x86_64:
>
> movl %edi, %eax
> sarl %eax
> xorl $1, %eax
> negl %eax
> cltq
>
> which should be faster than loading the value from memory. A quick
> unscientific test using
>
> `time make check-gcc RUNTESTFLAGS="dg.exp=builtin*"`
>
> shaves about half a second off execution time with this. Also simplify
> implementation of unknown_object_size.
>
> gcc/ChangeLog:
>
> * tree-object-size.c (unknown): Make into a function. Adjust
> all uses.
> (unknown_object_size): Simplify implementation.
>
> Signed-off-by: Siddhesh Poyarekar <siddh...@gotplt.org>
Ok for trunk if it passes bootstrap/regtest.
Jakub
