Re: [PATCH 1/2] simplify-rtx: The truncation of an IOR can have all bits set (PR81423)

[Jeff Law <law@redhat.com>]

On 08/07/2017 04:33 PM, Segher Boessenkool wrote:
> On Tue, Jul 25, 2017 at 06:25:49AM -0500, Segher Boessenkool wrote:
>> On Mon, Jul 24, 2017 at 04:06:39PM -0600, Jeff Law wrote:
>>>> 2017-07-24  Segher Boessenkool  <segher@kernel.crashing.org>
>>>>
>>>> gcc/testsuite/
>>>> 	PR rtl-optimization/81423
>>>> 	* gcc.c-torture/execute/pr81423.c: New testcase.
>>> I think int32plus just indicates ints are at least 32 bits. But a long
>>> or long long could still be just 32 bits.  so int32plus && long_neq_int,
>>> to ensure that long/long long are 64 bits?
>>
>> Well, long long is required to be 64 bits or more by the C standard.
>> But some GCC targets do not follow that, with certain options at least.
>>
>> It looks like that test actually requires long long to be *exactly*
>> 64 bits.  I'll modify the test to test for that.
> 
> So I came up with the following.  Is this okay for trunk?  (Tested on
> powerpc64-linux and x86_64-linux, both with both -m32 and -m64, and
> tested it does fail on x86 without the patches to fix the bug).
> 
> 
> Segher
> 
> 
> diff --git a/gcc/testsuite/gcc.c-torture/execute/pr81423.c b/gcc/testsuite/gcc.c-torture/execute/pr81423.c
> new file mode 100644
> index 0000000..731aa8f
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/execute/pr81423.c
> @@ -0,0 +1,36 @@
> +extern void abort (void);
> +
> +unsigned long long int ll = 0;
> +unsigned long long int ull1 = 1ULL;
> +unsigned long long int ull2 = 12008284144813806346ULL;
> +unsigned long long int ull3;
> +
> +unsigned long long int __attribute__ ((noinline))
> +foo (void)
> +{
> +  ll = -5597998501375493990LL;
> +
> +  ll = (5677365550390624949L - ll) - (ull1 > 0);
> +  unsigned long long int ull3;
> +  ull3 = (unsigned int)
> +    (2067854353L <<
> +     (((ll + -2129105131L) ^ 10280750144413668236ULL) -
> +      10280750143997242009ULL)) >> ((2873442921854271231ULL | ull2)
> +				    - 12098357307243495419ULL);
> +
> +  return ull3;
> +}
> +
> +int
> +main (void)
> +{
> +  /* We need a long long of exactly 64 bits for this test.  */
> +  ll--;
> +  if (ll != 0xffffffffffffffffULL)
> +    return 0;
I think we've used sizeof to check this in the past.  But I'm not wed to
that approach.  If it's working for you, then let's go with it.

jeff