Re: enable sqrt insns for cdce3.c

[Alexandre Oliva <oliva@adacore.com>]

[Revamped version of this patch, combined with others, to follow]

On Mar 10, 2021, Hans-Peter Nilsson <hp@bitrange.com> wrote:

> On Wed, 10 Mar 2021, Alexandre Oliva wrote:
>> 
>> The test expects shrink-wrapping of the fsqrt call, but that will only
>> occur when there is a usable sqrt insn.
>> 
>> Arrange for dejagnu to add the options that enable the sqrt insn, if
>> one is available, and to skip the test otherwise.
>> 
>> 
>> H-P, this *should* obviate the mmix-specific dg-skip-if.

> Unfortunately it doesn't.

>> Would it be
>> easy for you to confirm that this is the case and, if so, drop it?

> About as easy as for anyone (this is a compile-test), but no
> problem.  Unfortunately I get, with your patch applied and the
> dg-skip-if removed:

> FAIL: gcc.dg/cdce3.c scan-tree-dump cdce "cdce3.c:12: [^\n\r]*
> function call is shrink-wrapped into error conditions."

Is mmix a sqrt_insn effective target?  proc
check_effective_target_sqrt_insn in
gcc/testsuite/lib/target-supports.exp suggests it shouldn't pass, so I'm
surprised it would still try to run the test despite the added
/* { dg-require-effective-target sqrt_insn } */ directive.


> The dump files and assembly file show no obvious clues to me as
> to what is supposed to happen; attached.

cdce3 is supposed to shrink-wrap the sqrtf(x) call into something like
(x >= 0 ? .SQRT(x) : sqrtf(x)), where .SQRT stands for a square root
instruction.

Since we don't know why it still runs for you, I'm keeping the mmix
explicit skip in the new version of the patch.

Thanks,

-- 
Alexandre Oliva, happy hacker            https://FSFLA.org/blogs/lxo/
   Free Software Activist                   GNU Toolchain Engineer
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