[AArch64,testsuite] PR target/70004: Remove check using undefined behaviour

Hi all,

This test was reported as starting to fail a scan-assembler check with -mtune=thunderx.
The compiler decided to move the result back into the integer registers and perform the shift there
rather than do it on the SIMD side.
However, the C code is undefined because the shift is wider than the type. GCC even warns for it, but the
test catches it with dg-warning.
I don't think it's correct for the test to rely on undefined code, so the simplest thing to do is to delete
the undefined code.

Ok for trunk?

Thanks,
Kyrill

2016-03-01  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     PR target/70004
     * gcc.target/aarch64/scalar_shift_1.c: (test_corners_sisd_di):
     Delete.
     (test_corners_sisd_si): Likewise.
     (main): Remove checks of the above.

On Tue, Mar 01, 2016 at 02:29:19PM +0000, Kyrill Tkachov wrote:
> This test was reported as starting to fail a scan-assembler check with -mtune=thunderx.
> The compiler decided to move the result back into the integer registers and perform the shift there
> rather than do it on the SIMD side.
> However, the C code is undefined because the shift is wider than the type. GCC even warns for it, but the
> test catches it with dg-warning.
> I don't think it's correct for the test to rely on undefined code, so the simplest thing to do is to delete
> the undefined code.
> 
> Ok for trunk?
> 
> Thanks,
> Kyrill
> 
> 2016-03-01  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
> 
>     PR target/70004
>     * gcc.target/aarch64/scalar_shift_1.c: (test_corners_sisd_di):
>     Delete.
>     (test_corners_sisd_si): Likewise.
>     (main): Remove checks of the above.

I think you should extend this patch, by adding the removed functions
into another, dg-do compile only test without any scan-assembler stuff in
there, just to make sure you don't ICE on it and emit the warnings that
should be emitted, and possibly by keeping the well defined corner case
stuff in there instead of removing the functions altogether.  b >> 63 and
b >> 0 are both well defined, similarly b >> 31 and b >> 0 in the other
function.

> diff --git a/gcc/testsuite/gcc.target/aarch64/scalar_shift_1.c b/gcc/testsuite/gcc.target/aarch64/scalar_shift_1.c
> index 8465c896705dbfd4c76b0815511ea7b4b034e095..7be1b12a75bf9f201644aef471c5edb99979c0c5 100644
> --- a/gcc/testsuite/gcc.target/aarch64/scalar_shift_1.c
> +++ b/gcc/testsuite/gcc.target/aarch64/scalar_shift_1.c
> @@ -181,34 +181,6 @@ test_ashift_right_int_si (Int32x1 b, Int32x1 c)
>  /* { dg-final { scan-assembler "asr\tw\[0-9\]+,\ w\[0-9\]+,\ 4" } } */
>  /* { dg-final { scan-assembler "asr\tw\[0-9\]+,\ w\[0-9\]+,\ w\[0-9\]+" } } */
>  
> -Int64x1
> -test_corners_sisd_di (Int64x1 b)
> -{
> -  force_simd_di (b);
> -  b = b >> 63;
> -  force_simd_di (b);
> -  b = b >> 0;
> -  b += b >> 65; /* { dg-warning "right shift count >= width of type" } */
> -
> -  return b;
> -}
> -/* { dg-final { scan-assembler "sshr\td\[0-9\]+,\ d\[0-9\]+,\ 63" } } */
> -
> -Int32x1
> -test_corners_sisd_si (Int32x1 b)
> -{
> -  force_simd_si (b);
> -  b = b >> 31;
> -  force_simd_si (b);
> -  b = b >> 0;
> -  b += b >> 33; /* { dg-warning "right shift count >= width of type" } */
> -
> -  return b;
> -}
> -/* { dg-final { scan-assembler "sshr\tv\[0-9\]+\.2s,\ v\[0-9\]+\.2s,\ 31" } } */
> -
> -
> -
>  #define CHECK(var,val) \
>  do                     \
>    {                    \
> @@ -236,8 +208,6 @@ main ()
>    CHECK (x, 0xffffffff21524110ull);
>    x = test_ashift_right_sisd_di (x, 8);
>    CHECK (x, 0xffffffffffff2152ull);
> -  x = test_corners_sisd_di (x);
> -  CHECK (x, 0xfffffffffffffffeull);
>  
>    y = test_lshift_left_sisd_si (y, 4);
>    CHECK (y, 0xadbeef00);
> @@ -252,8 +222,6 @@ main ()
>    CHECK (y, 0xffff5241);
>    y = test_ashift_right_sisd_si (y, 4);
>    CHECK (y, 0xffffff52);
> -  y = test_corners_sisd_si (y);
> -  CHECK (y, 0xfffffffe);
>  
>    return 0;
>  }


	Jakub