Re: [PATCH, ARM/Thumb1] Adjust rtx cost to prevent expanding MULT into shift/add instructions

[Richard Earnshaw <rearnsha at arm dot com>]

On 24/07/13 03:36, Terry Guo wrote:
> Hi there,
>
> This patch intends to update thumb1_size_rtx_costs function to correctly
> handle those RTXs defined by RTL expansion pass. Thus the GIMPLE
> multiplication will be expanded to single mul instruction instead of a bunch
> of shift/add/sub instructions which are in fact more expensive.
>
> Tested with GCC regression test on QEMU ARM926, no regression. Is it OK to
> trunk and 4.8 branch?
>
> BR,
> Terry
>
>
> gcc/ChangeLog:
> 2013-07-24  Terry Guo  <terry.guo@arm.com>
>
>          * config/arm/arm.c (thumb1_size_rtx_costs): Assign proper cost for
>          shift_add/shift_sub0/shift_sub1 RTXs.
>
> gcc/testsuite/ChangeLog:
> 2013-07-24  Terry Guo  <terry.guo@arm.com>
>
>          * gcc.target/arm/thumb1-Os-mult.c: New test case.

OK.

I'll note for the record, though, that that function needs a major 
rewrite...

R.