On 04/07/17 15:39, Kyrill Tkachov wrote:
> Hi all,
>
> While doing some unrelated work the
> gcc.target/aarch64/simd/vminmaxnm_1.c testcase started failing for me.
> Upon investigation it turns out that it breaks the C strict aliasing
> rules in the CHECK macro by casting
> a pointer to an incompatible type and dereferencing it. GCC even warns
> about it if compiled with -Wstrict-aliasing.
>
> This patch fixes the testcase by making it use memcmp to compare the
> vector elements.
> This avoids the undefined behaviour.
>
> The testcase still passes on trunk.
> Ok to commit?
>
> Thanks,
> Kyrill
>
> 2017-07-04 Kyrylo Tkachov <[email protected]>
>
> * gcc.target/aarch64/simd/vminmaxnm_1.c: Fix strict aliasing issues.
>
OK.
R.
> vmaxmin-aliasing.patch
>
>
> diff --git a/gcc/testsuite/gcc.target/aarch64/simd/vminmaxnm_1.c
> b/gcc/testsuite/gcc.target/aarch64/simd/vminmaxnm_1.c
> index 192bad9..8fd4281 100644
> --- a/gcc/testsuite/gcc.target/aarch64/simd/vminmaxnm_1.c
> +++ b/gcc/testsuite/gcc.target/aarch64/simd/vminmaxnm_1.c
> @@ -7,12 +7,10 @@
>
> extern void abort ();
>
> -#define CHECK(T, N, R, E) \
> +#define CHECK(R, E) \
> {\
> - int i = 0;\
> - for (; i < N; i++)\
> - if (* (T *) &R[i] != * (T *) &E[i])\
> - abort ();\
> + if (__builtin_memcmp (&R, &E, sizeof (R)) != 0)\
> + abort ();\
> }
>
> int
> @@ -26,8 +24,8 @@ main (int argc, char **argv)
> float32x2_t f32x2_ret_minnm = vminnm_f32 (f32x2_input1, f32x2_input2);
> float32x2_t f32x2_ret_maxnm = vmaxnm_f32 (f32x2_input1, f32x2_input2);
>
> - CHECK (uint32_t, 2, f32x2_ret_minnm, f32x2_exp_minnm);
> - CHECK (uint32_t, 2, f32x2_ret_maxnm, f32x2_exp_maxnm);
> + CHECK (f32x2_ret_minnm, f32x2_exp_minnm);
> + CHECK (f32x2_ret_maxnm, f32x2_exp_maxnm);
>
> /* v{min|max}nm_f32 NaN. */
> f32x2_input1 = vdup_n_f32 (__builtin_nanf (""));
> @@ -37,8 +35,8 @@ main (int argc, char **argv)
> f32x2_ret_minnm = vminnm_f32 (f32x2_input1, f32x2_input2);
> f32x2_ret_maxnm = vmaxnm_f32 (f32x2_input1, f32x2_input2);
>
> - CHECK (uint32_t, 2, f32x2_ret_minnm, f32x2_exp_minnm);
> - CHECK (uint32_t, 2, f32x2_ret_maxnm, f32x2_exp_maxnm);
> + CHECK (f32x2_ret_minnm, f32x2_exp_minnm);
> + CHECK (f32x2_ret_maxnm, f32x2_exp_maxnm);
>
> /* v{min|max}nmq_f32 normal. */
> float32x4_t f32x4_input1 = vdupq_n_f32 (-1024.0);
> @@ -48,8 +46,8 @@ main (int argc, char **argv)
> float32x4_t f32x4_ret_minnm = vminnmq_f32 (f32x4_input1, f32x4_input2);
> float32x4_t f32x4_ret_maxnm = vmaxnmq_f32 (f32x4_input1, f32x4_input2);
>
> - CHECK (uint32_t, 4, f32x4_ret_minnm, f32x4_exp_minnm);
> - CHECK (uint32_t, 4, f32x4_ret_maxnm, f32x4_exp_maxnm);
> + CHECK (f32x4_ret_minnm, f32x4_exp_minnm);
> + CHECK (f32x4_ret_maxnm, f32x4_exp_maxnm);
>
> /* v{min|max}nmq_f32 NaN. */
> f32x4_input1 = vdupq_n_f32 (-__builtin_nanf (""));
> @@ -59,8 +57,8 @@ main (int argc, char **argv)
> f32x4_ret_minnm = vminnmq_f32 (f32x4_input1, f32x4_input2);
> f32x4_ret_maxnm = vmaxnmq_f32 (f32x4_input1, f32x4_input2);
>
> - CHECK (uint32_t, 4, f32x4_ret_minnm, f32x4_exp_minnm);
> - CHECK (uint32_t, 4, f32x4_ret_maxnm, f32x4_exp_maxnm);
> + CHECK (f32x4_ret_minnm, f32x4_exp_minnm);
> + CHECK (f32x4_ret_maxnm, f32x4_exp_maxnm);
>
> /* v{min|max}nm_f64 normal. */
> float64x1_t f64x1_input1 = vdup_n_f64 (1.23);
> @@ -69,16 +67,16 @@ main (int argc, char **argv)
> float64x1_t f64x1_exp_maxnm = vdup_n_f64 (4.56);
> float64x1_t f64x1_ret_minnm = vminnm_f64 (f64x1_input1, f64x1_input2);
> float64x1_t f64x1_ret_maxnm = vmaxnm_f64 (f64x1_input1, f64x1_input2);
> - CHECK (uint64_t, 1, f64x1_ret_minnm, f64x1_exp_minnm);
> - CHECK (uint64_t, 1, f64x1_ret_maxnm, f64x1_exp_maxnm);
> + CHECK (f64x1_ret_minnm, f64x1_exp_minnm);
> + CHECK (f64x1_ret_maxnm, f64x1_exp_maxnm);
>
> /* v{min|max}_f64 normal. */
> float64x1_t f64x1_exp_min = vdup_n_f64 (1.23);
> float64x1_t f64x1_exp_max = vdup_n_f64 (4.56);
> float64x1_t f64x1_ret_min = vmin_f64 (f64x1_input1, f64x1_input2);
> float64x1_t f64x1_ret_max = vmax_f64 (f64x1_input1, f64x1_input2);
> - CHECK (uint64_t, 1, f64x1_ret_min, f64x1_exp_min);
> - CHECK (uint64_t, 1, f64x1_ret_max, f64x1_exp_max);
> + CHECK (f64x1_ret_min, f64x1_exp_min);
> + CHECK (f64x1_ret_max, f64x1_exp_max);
>
> /* v{min|max}nmq_f64 normal. */
> float64x2_t f64x2_input1 = vdupq_n_f64 (1.23);
> @@ -87,8 +85,8 @@ main (int argc, char **argv)
> float64x2_t f64x2_exp_maxnm = vdupq_n_f64 (4.56);
> float64x2_t f64x2_ret_minnm = vminnmq_f64 (f64x2_input1, f64x2_input2);
> float64x2_t f64x2_ret_maxnm = vmaxnmq_f64 (f64x2_input1, f64x2_input2);
> - CHECK (uint64_t, 2, f64x2_ret_minnm, f64x2_exp_minnm);
> - CHECK (uint64_t, 2, f64x2_ret_maxnm, f64x2_exp_maxnm);
> + CHECK (f64x2_ret_minnm, f64x2_exp_minnm);
> + CHECK (f64x2_ret_maxnm, f64x2_exp_maxnm);
>
> /* v{min|max}nm_f64 NaN. */
> f64x1_input1 = vdup_n_f64 (-__builtin_nanf (""));
> @@ -98,8 +96,8 @@ main (int argc, char **argv)
> f64x1_ret_minnm = vminnm_f64 (f64x1_input1, f64x1_input2);
> f64x1_ret_maxnm = vmaxnm_f64 (f64x1_input1, f64x1_input2);
>
> - CHECK (uint64_t, 1, f64x1_ret_minnm, f64x1_exp_minnm);
> - CHECK (uint64_t, 1, f64x1_ret_maxnm, f64x1_exp_maxnm);
> + CHECK (f64x1_ret_minnm, f64x1_exp_minnm);
> + CHECK (f64x1_ret_maxnm, f64x1_exp_maxnm);
>
> /* v{min|max}_f64 NaN. */
> f64x1_input1 = vdup_n_f64 (-__builtin_nanf (""));
> @@ -109,8 +107,8 @@ main (int argc, char **argv)
> f64x1_ret_minnm = vmin_f64 (f64x1_input1, f64x1_input2);
> f64x1_ret_maxnm = vmax_f64 (f64x1_input1, f64x1_input2);
>
> - CHECK (uint64_t, 1, f64x1_ret_minnm, f64x1_exp_minnm);
> - CHECK (uint64_t, 1, f64x1_ret_maxnm, f64x1_exp_maxnm);
> + CHECK (f64x1_ret_minnm, f64x1_exp_minnm);
> + CHECK (f64x1_ret_maxnm, f64x1_exp_maxnm);
>
> /* v{min|max}nmq_f64 NaN. */
> f64x2_input1 = vdupq_n_f64 (-__builtin_nan (""));
> @@ -120,8 +118,8 @@ main (int argc, char **argv)
> f64x2_ret_minnm = vminnmq_f64 (f64x2_input1, f64x2_input2);
> f64x2_ret_maxnm = vmaxnmq_f64 (f64x2_input1, f64x2_input2);
>
> - CHECK (uint64_t, 2, f64x2_ret_minnm, f64x2_exp_minnm);
> - CHECK (uint64_t, 2, f64x2_ret_maxnm, f64x2_exp_maxnm);
> + CHECK (f64x2_ret_minnm, f64x2_exp_minnm);
> + CHECK (f64x2_ret_maxnm, f64x2_exp_maxnm);
>
> return 0;
> }
>
