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Re: [PATCH][ARM/AArch64] Properly cost rev16 operand

On Fri, May 01, 2015 at 09:24:20AM +0100, Kyrill Tkachov wrote:
> Hi all,
> It occurs to me that in the IOR-of-shifts form of the rev16 operation we
> should be costing the operand properly.  For that we'd want to reuse the
> aarch_rev16_p function that does all the heavy lifting and get it to write
> the innermost operand of the rev16 for further costing. In the process we
> relax that function a bit to accept any rtx as the operand, not just REGs so
> that we can calculate the cost of moving them in a register appropriately.
> This patch does just that and updates the arm and aarch64 callsites
> appropriately so that the operands are processed properly.
> In practice I don't expect this to make much difference since this patterns
> occurs rarely anyway, but it seems like the 'right thing to do' (TM).
> Bootstrapped and tested on arm,aarch64.
> Ok for trunk?

Looks OK for aarch64, please wait for an Ack from an arm maintainer.


> 2015-05-01  Kyrylo Tkachov  <>
>      * config/arm/aarch-common-protos.h (aarch_rev16_p): Update signature
>      to take a second argument.
>      * config/arm/aarch-common.c (aarch_rev16_p): Add second argument.
>      Write inner-most rev16 argument to it if recognised.
>      (aarch_rev16_p_1): Likewise.
>      * config/arm/arm.c (arm_new_rtx_costs): Properly cost rev16 operand
>      in the IOR case.
>      * config/aarch64/aarch64.c (aarch64_rtx_costs): Likewise.

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