[PATCH][ARM] use vsel instruction for floating point conditional moves in ARMv8

Ramana Radhakrishnan ramrad01@arm.com
Mon Feb 18 11:51:00 GMT 2013


On 01/30/13 09:24, Kyrylo Tkachov wrote:
> Hi all,
> This patch uses the new ARMv8 AArch32 vsel instruction to implement
> conditional moves of floating point numbers.
> For example, an instruction of the form:
> 	vsel<cond>.f32  s0, s1, s2
> means
> 	s0 := cond ? s1 : s2
>
> This can be useful, among other places, in Thumb2 because it doesn't require
> an enclosing IT block.
> A small catch: The condition code used in vsel can only be one of {GE, GT,
> EQ, VS}. If we want to use their negations {LT, LE, NE, VC} we just flip the
> source operands.
> A new predicate is introduced that checks that the comparison yields an ARM
> condition code in the set {GE, GT, EQ, VS, LT, LE, NE, VC}.
>
> New compilation tests are added. They pass on a model and no new regressions
> on arm-none-eabi with qemu.

>
> Ok for trunk?

Ok for stage1 4.9.

ramana

>
> Thanks,
> Kyrill
>
> gcc/ChangeLog
>
> 2013-01-30  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
> 	* config/arm/arm.md (f_sels, f_seld): New types.
> 	(*cmov<mode>): New pattern.
> 	* config/arm/predicates.md (arm_vsel_comparison_operator): New
> predicate.	
>
>
> gcc/testsuite/ChangeLog
>
> 2013-01-30  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>
> 	* gcc.target/arm/vseleqdf.c: New test.
> 	* gcc.target/arm/vseleqsf.c: Likewise.
> 	* gcc.target/arm/vselgedf.c: Likewise.
> 	* gcc.target/arm/vselgesf.c: Likewise.
> 	* gcc.target/arm/vselgtdf.c: Likewise.
> 	* gcc.target/arm/vselgtsf.c: Likewise.
> 	* gcc.target/arm/vselledf.c: Likewise.
> 	* gcc.target/arm/vsellesf.c: Likewise.
> 	* gcc.target/arm/vselltdf.c: Likewise.
> 	* gcc.target/arm/vselltsf.c: Likewise.
> 	* gcc.target/arm/vselnedf.c: Likewise.
> 	* gcc.target/arm/vselnesf.c: Likewise.
> 	* gcc.target/arm/vselvcdf.c: Likewise.
> 	* gcc.target/arm/vselvcsf.c: Likewise.
> 	* gcc.target/arm/vselvsdf.c: Likewise.
> 	* gcc.target/arm/vselvssf.c: Likewise.
>




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