The following testcase is miscompiled. The problem is that during
RTL DSE we see a V4DI register is being loaded { 16, 16, 0, 0 }
value and DSE mostly works in terms of scalar modes, so it calls
movoi to set an OImode REG to (const_wide_int 0x100000000000000010)
and ix86_convert_const_wide_int_to_broadcast thinks it can compute
that value by broadcasting DImode 0x10. While it is true that
for TImode result the broadcast could be used, for OImode/XImode
it can't be, because all but the lowest 2 HOST_WIDE_INTs aren't
present (so are 0 or -1 depending on sign), not 0x10 in this case.
The function checks if the least significant HOST_WIDE_INT elt
of the CONST_WIDE_INT is broadcastable from QI/HI/SI/DImode and then
/* Check if OP can be broadcasted from VAL. */
for (int i = 1; i < CONST_WIDE_INT_NUNITS (op); i++)
if (val != CONST_WIDE_INT_ELT (op, i))
return nullptr;
That is needed of course, but nothing checks that
CONST_WIDE_INT_NUNITS (op) isn't too small for the mode in question.
I think if op would be 0 or -1, it ought to be never CONST_WIDE_INT,
but CONST_INT and so we can just punt whenever the number of
CONST_WIDE_INT elts is not the expected one.
2023-01-31 Jakub Jelinek <jakub@redhat.com>
PR target/108599
* config/i386/i386-expand.cc
(ix86_convert_const_wide_int_to_broadcast): Return nullptr if
CONST_WIDE_INT_NUNITS (op) times HOST_BITS_PER_WIDE_INT isn't
equal to bitsize of mode.
* gcc.target/i386/avx2-pr108599.c: New test.
(cherry picked from commit
963315a922e228c4f6853826666151fc540f111a)
broadcast only if vector broadcast is available. */
if (!TARGET_AVX
|| !CONST_WIDE_INT_P (op)
- || standard_sse_constant_p (op, mode))
+ || standard_sse_constant_p (op, mode)
+ || (CONST_WIDE_INT_NUNITS (op) * HOST_BITS_PER_WIDE_INT
+ != GET_MODE_BITSIZE (mode)))
return nullptr;
HOST_WIDE_INT val = CONST_WIDE_INT_ELT (op, 0);
--- /dev/null
+/* PR target/108599 */
+/* { dg-do run { target avx2 } } */
+/* { dg-options "-O2 -mavx2 -mtune=skylake-avx512" } */
+
+#include "avx2-check.h"
+
+struct S { unsigned long long a, b, c, d; };
+
+__attribute__((noipa)) void
+foo (unsigned long long x, unsigned long long y,
+ unsigned long long z, unsigned long long w, const struct S s)
+{
+ if (s.a != x || s.b != y || s.c != z || s.d != w)
+ abort ();
+}
+
+typedef unsigned long long V __attribute__((may_alias, vector_size (4 * sizeof (unsigned long long))));
+
+static void
+avx2_test (void)
+{
+ {
+ struct S s;
+ *(V *)&s = (V) { 16, 0, 0, 0 };
+ foo (16, 0, 0, 0, s);
+ }
+ {
+ struct S s;
+ *(V *)&s = (V) { 16, 16, 0, 0 };
+ foo (16, 16, 0, 0, s);
+ }
+}