On 24/07/15 12:27, Kyrill Tkachov wrote:
> On 24/07/15 12:10, Szabolcs Nagy wrote:
>> (-a)*b should not be compiled to vnmul a,b with -frounding-math.
>> Added a new -(a*b) pattern for vnmul and the old one is only
>> used if !flag_rounding_math.  Updated the costs too.
>>
>> This is the ARM version of
>> https://gcc.gnu.org/ml/gcc-patches/2015-07/msg00300.html
>>
>> Tested with arm-none-linux-gnueabihf cross compiler.
>> is this OK?
>>
>> gcc/Changelog:
>>
>> 2015-07-20  Szabolcs Nagy  <szabolcs.nagy@arm.com>
>>
>> 	PR target/66731
>> 	* config/arm/arm.md (muldf3negdf_vfp): Handle -frounding-math.
>> 	(mulsf3negsf_vfp): Likewise.
>
> This entry is misleading. You disable two existing patterns
> for flag_rounding_math and you add two new patterns. The
> entry should reflect that.
..
> Can you give the new pattern a different name to reflect that
> the neg is on the outside? Something like *negmulsf3_vfp.
..
> +/* { dg-options "-O2 -mfpu=vfp -mfloat-abi=hard" } */
>
> Can you please add an explicit -fno-rounding-math here? That way we get a hint as to
> why these tests exist. Alternatively, you can rename the tests to be pr66731_1.c,
> pr66731_2.c etc. That way in the future we'll know what issue they're testing for.
..
> +float
> +foo_s (float a, float b)
> +{
> +  /* { dg-final { scan-assembler "vneg\.f32" } } */
> +  /* { dg-final { scan-assembler "vmul\.f32" } } */
> +  return -a * b;
> +}
>
> I'd prefer if you just do a scan-assembler not "vnmul", which is what this
> patch really fixes. Whether the midend decides to use a pair of vneg+vmul
> is tangential to this patch, it's the vnmul that we're trying to avoid.

[v2]:
- used different names for the new patterns
- fixed change log accordingly
- used explicit -fno-rounding-math in tests
- used scan-assembler-not "vnmul"

(I havent changed the names of the tests to be
consistent with the aarch64 patches but if ppl
prefer pr<N>.c name I can do that.)

gcc/Changelog:

2015-07-28  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	PR target/66731
	* config/arm/arm.md (negmuldf3_vfp): Add new pattern.
	(negmulsf3_vfp): Likewise.
	(muldf3negdf_vfp): Disable for -frounding-math.
	(mulsf3negsf_vfp): Likewise.
	* config/arm/arm.c (arm_new_rtx_costs): Fix NEG cost for VNMUL,
	fix MULT cost with -frounding-math.

gcc/testsuite/Changelog:

2015-07-28  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	PR target/66731
	* gcc.target/arm/vnmul-1.c: New.
	* gcc.target/arm/vnmul-2.c: New.
	* gcc.target/arm/vnmul-3.c: New.
	* gcc.target/arm/vnmul-4.c: New.