[PATCH PR94442] [AArch64] Redundant ldp/stp instructions emitted at -O3

Richard Sandiford richard.sandiford@arm.com
Wed Aug 19 10:06:25 GMT 2020


xiezhiheng <xiezhiheng@huawei.com> writes:
> I add FLAGS for part of intrinsics in aarch64-simd-builtins.def first for a try,
> including all the add/sub arithmetic intrinsics.
>
> Something like faddp intrinsic which only handles floating-point operations,
> both FP and NONE flags are suitable for it because FLAG_FP will be added
> later if the intrinsic handles floating-point operations.  And I prefer FP since
> it would be more clear.

Sounds good to me.

> But for qadd intrinsics, they would modify FPSR register which is a scenario
> I missed before.  And I consider to add an additional flag FLAG_WRITE_FPSR
> to represent it.

I don't think we make any attempt to guarantee that the Q flag is
meaningful after saturating intrinsics.  To do that, we'd need to model
the modification of the flag in the .md patterns too.

So my preference would be to leave this out and just use NONE for the
saturating forms too.

Thanks,
Richard


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