[PATCH, ARM] Suppress Redundant Flag Setting for Cortex-A15
Tue Jan 28 12:10:00 GMT 2014
On Fri, Jan 24, 2014 at 5:16 PM, Ian Bolton <email@example.com> wrote:
> Hi there!
> An existing optimisation for Thumb-2 converts t32 encodings to
> t16 encodings to reduce codesize, at the expense of causing
> redundant flag setting for ADD, AND, etc. This redundant flag
> setting can have negative performance impact on cortex-a15.
> This patch introduces two new tuning options so that the conversion
> from t32 to t16, which takes place in thumb2_reorg, can be suppressed
> for cortex-a15.
> To maintain some of the original benefit (reduced codesize), the
> suppression is only done where the enclosing basic block is deemed
> worthy of optimising for speed.
> This tested with no regressions and performance has improved for
> the workloads tested on cortex-a15. (It might be beneficial to
> other processors too, but that has not been investigated yet.)
> OK for stage 1?
This is OK for stage1.
> 2014-01-24 Ian Bolton <firstname.lastname@example.org>
> * config/arm/arm-protos.h (tune_params): New struct members.
> * config/arm/arm.c: Initialise tune_params per processor.
> (thumb2_reorg): Suppress conversion from t32 to t16 when
> optimizing for speed, based on new tune_params.
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