[PATCH][GCC][ARM] Disable neon testing for armv7-m

[Andre Vieira]

On 16/11/15 12:07, James Greenhalgh wrote:
> On Mon, Nov 16, 2015 at 10:49:11AM +0000, Andre Vieira wrote:
>> Hi,
>>
>>    This patch changes the target support mechanism to make it
>> recognize any ARM 'M' profile as a non-neon supporting target. The
>> current check only tests for armv6 architectures and earlier, and
>> does not account for armv7-m.
>>
>>    This is correct because there is no 'M' profile that supports neon
>> and the current test is not sufficient to exclude armv7-m.
>>
>>    Tested by running regressions for this testcase for various ARM targets.
>>
>>    Is this OK to commit?
>>
>>    Thanks,
>>    Andre Vieira
>>
>> gcc/testsuite/ChangeLog:
>> 2015-11-06  Andre Vieira  <andre.simoesdiasvieira@arm.com>
>>
>>          * gcc/testsuite/lib/target-supports.exp
>>            (check_effective_target_arm_neon_ok_nocache): Added check
>>            for M profile.
>
>>  From 2c53bb9ba3236919ecf137a4887abf26d4f7fda2 Mon Sep 17 00:00:00 2001
>> From: Andre Simoes Dias Vieira <andsim01@arm.com>
>> Date: Fri, 13 Nov 2015 11:16:34 +0000
>> Subject: [PATCH] Disable neon testing for armv7-m
>>
>> ---
>>   gcc/testsuite/lib/target-supports.exp | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
>> index 75d506829221e3d02d454631c4bd2acd1a8cedf2..8097a4621b088a93d58d09571cf7aa27b8d5fba6 100644
>> --- a/gcc/testsuite/lib/target-supports.exp
>> +++ b/gcc/testsuite/lib/target-supports.exp
>> @@ -2854,7 +2854,7 @@ proc check_effective_target_arm_neon_ok_nocache { } {
>>   		int dummy;
>>   		/* Avoid the case where a test adds -mfpu=neon, but the toolchain is
>>   		   configured for -mcpu=arm926ej-s, for example.  */
>> -		#if __ARM_ARCH < 7
>> +		#if __ARM_ARCH < 7 || __ARM_ARCH_PROFILE == 'M'
>>   		#error Architecture too old for NEON.
>
> Could you fix this #error message while you're here?
>
> Why we can't change this test to look for the __ARM_NEON macro from ACLE:
>
> #if __ARM_NEON < 1
>    #error NEON is not enabled
> #endif
>
> Thanks,
> James
>

There is a check for this already: 'check_effective_target_arm_neon'. I 
think the idea behind arm_neon_ok is to check whether the hardware would 
support neon, whereas arm_neon is to check whether neon was enabled, 
i.e. -mfpu=neon was used or a mcpu was passed that has neon enabled by 
default.

The comments for 'check_effective_target_arm_neon_ok_nocache' highlight 
this, though maybe the comments for check_effective_target_arm_neon 
could be better.

# Return 1 if this is an ARM target supporting -mfpu=neon
# -mfloat-abi=softfp or equivalent options.  Some multilibs may be
# incompatible with these options.  Also set et_arm_neon_flags to the
# best options to add.

proc check_effective_target_arm_neon_ok_nocache
...
/* Avoid the case where a test adds -mfpu=neon, but the toolchain is
                    configured for -mcpu=arm926ej-s, for example.  */
...


and

# Return 1 if this is a ARM target with NEON enabled.

proc check_effective_target_arm_neon
...

Cheers,
Andre