Hi! The AVX512{F,VL} vector comparisons that set %kN registers are represented in RTL as comparisons with vector mode operands and scalar integral result, where at runtime the scalar integer is filled with a bitmask. Unfortunately, simplify_relational_operation would fold e.g. (eq:SI (reg:V32HI x) (reg:V32HI x)) into (const_int 1) rather than (const_int -1) that is expected (all elements equal). simplify_const_relational_operation is documented to always return just const0_rtx or const_true_rtx and simplify_relational_operation is expected to fix this up, for vector comparisons with vector result it duplicates the 0 or -1 into all elements, etc., so this patch adds handling for this case there too.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2019-12-11 Jakub Jelinek <ja...@redhat.com> PR target/92908 * simplify-rtx.c (simplify_relational_operation): For vector cmp_mode and scalar mode, if simplify_relational_operation returned const_true_rtx, return a scalar bitmask of all ones. (simplify_const_relational_operation): Change VOID_mode in function comment to VOIDmode. * gcc.target/i386/avx512bw-pr92908.c: New test. --- gcc/simplify-rtx.c.jj 2019-11-19 22:27:02.000058742 +0100 +++ gcc/simplify-rtx.c 2019-12-11 13:31:57.197809704 +0100 @@ -5037,6 +5037,23 @@ simplify_relational_operation (enum rtx_ return NULL_RTX; #endif } + if (VECTOR_MODE_P (cmp_mode) + && SCALAR_INT_MODE_P (mode) + && tem == const_true_rtx) + { + /* Vector comparisons that expect a scalar integral + bitmask. For const0_rtx the result is already correct, + for const_true_rtx we need all bits set. */ + int n_elts; + scalar_int_mode smode = as_a <scalar_int_mode> (mode); + gcc_assert (GET_MODE_NUNITS (cmp_mode).is_constant (&n_elts) + && GET_MODE_PRECISION (smode) <= n_elts); + if (GET_MODE_PRECISION (smode) == n_elts) + return constm1_rtx; + if (n_elts < HOST_BITS_PER_WIDE_INT) + return GEN_INT ((HOST_WIDE_INT_1U << n_elts) - 1); + return NULL_RTX; + } return tem; } @@ -5383,7 +5400,7 @@ comparison_result (enum rtx_code code, i } /* Check if the given comparison (done in the given MODE) is actually - a tautology or a contradiction. If the mode is VOID_mode, the + a tautology or a contradiction. If the mode is VOIDmode, the comparison is done in "infinite precision". If no simplification is possible, this function returns zero. Otherwise, it returns either const_true_rtx or const0_rtx. */ --- gcc/testsuite/gcc.target/i386/avx512bw-pr92908.c.jj 2019-12-11 14:24:12.083418762 +0100 +++ gcc/testsuite/gcc.target/i386/avx512bw-pr92908.c 2019-12-11 14:23:56.071665326 +0100 @@ -0,0 +1,21 @@ +/* PR target/92908 */ +/* { dg-do run } */ +/* { dg-options "-Og -fno-tree-fre -mavx512bw" } */ +/* { dg-require-effective-target avx512bw } */ + +#define AVX512BW +#include "avx512f-helper.h" + +typedef unsigned short V __attribute__ ((__vector_size__ (64))); + +V v; + +void +TEST (void) +{ + int i; + v = (V) v == v; + for (i = 0; i < 32; i++) + if (v[i] != 0xffff) + abort (); +} Jakub