[PATCH] hppa: Improve hppa_rtx_costs for shifts by constants.

Jeff Law law@redhat.com
Thu Aug 27 18:15:08 GMT 2020

On Thu, 2020-08-27 at 17:42 +0100, Roger Sayle wrote:
> Hi Dave (and Jeff),
> For your consideration, here's a patch that should fix the recent regression
> of gcc.dg/tree-ssa/slrt-13.c on hppa targets.
> This patch provides more accurate rtx_costs estimates for shifts by
> integer constants (which are cheaper than by a register amount).
> Fine tuning these is sufficient to have simple-ssa-strength-reduce
> prefer multiplications by four, over multiplications by five.
> Technically only the ASHIFT is required to fix the regression, but for
> symmetry
> I've added the appropriate PA-RISC values for all three shift types (in
> SImode).
> I've also checked that this doesn't reintroduce PR middle-end/87256.
> I was wondering whether you could please "put this in the queue", and
> reconfirm that PR middle-end/87256 remains resolved?
> 2020-08-27  Roger Sayle  <roger@nextmovesoftware.com>
> gcc/ChangeLog
> 	* config/pa/pa.c (hppa_rtx_costs) [ASHIFT, ASHIFTRT, LSHIFTRT]:
> 	Provide accurate costs for shifts of integer constants.
Spinning in the tester.  Figure results about this time tomorrow:


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