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

[Kyrill Tkachov]

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?

Thanks,
Kyrill

2015-05-01  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     * 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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