Re: [PATCH 10/10] Port testsuite to GCN

[Andrew Stubbs <ams@codesourcery.com>]

I finally got back to investigating this ....

On 21/11/2018 01:00, Jeff Law wrote:
>> --- a/gcc/testsuite/gcc.dg/gimplefe-28.c
>> +++ b/gcc/testsuite/gcc.dg/gimplefe-28.c
>> @@ -1,5 +1,5 @@
>>   /* { dg-do compile { target sqrt_insn } } */
>> -/* { dg-options "-fgimple -O2" } */
>> +/* { dg-options "-fgimple -O2 -ffast-math" } */
> So why does the GCN need fast-math here?  I'm not aware of any other
> target  that needs that kind of handling to make this test work.

It needs it because the sqrt instruction is only enabled when 
flag_unsafe_math_optimizations is set. This seems appropriate given the 
approximate nature of the machine instruction.

This test uses gimple directly and so bypasses the usual optab checks 
that would normally select a library function instead, which results in 
an ICE.

It seems like a safe change to make, since most targets will have more 
patterns enabled, not fewer, in this mode.

The test will continue to fail on any target that does not have a sqrt 
instruction at all.

Andrew