https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110445
Bug ID: 110445
Summary: [14 Regression] FAIL: gcc.dg/vect/slp-46.c with AVX2
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: testsuite
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
Target Milestone: ---
With AVX2 we fail to SLP
double x[1024], y[1024];
void __attribute__((noipa)) foo()
{
for (int i = 0; i < 512; ++i)
{
x[2*i] = y[i];
x[2*i+1] = y[i];
}
}
because we hit the following:
/space/rguenther/src/gcc11queue/gcc/testsuite/gcc.dg/vect/slp-46.c:10:21: note:
==> examining statement: _2 = y[i_12];
/space/rguenther/src/gcc11queue/gcc/testsuite/gcc.dg/vect/slp-46.c:10:21:
missed: peeling for gaps insufficient for access
/space/rguenther/src/gcc11queue/gcc/testsuite/gcc.dg/vect/slp-46.c:12:17:
missed: not vectorized: relevant stmt not supported: _2 = y[i_12];
/space/rguenther/src/gcc11queue/gcc/testsuite/gcc.dg/vect/slp-46.c:10:21: note:
removing SLP instance operations starting from: x[_1] = _2;
/space/rguenther/src/gcc11queue/gcc/testsuite/gcc.dg/vect/slp-46.c:10:21:
missed: unsupported SLP instances
/space/rguenther/src/gcc11queue/gcc/testsuite/gcc.dg/vect/slp-46.c:10:21: note:
re-trying with SLP disabled
the issue is that in the last vector iteration with VF=2 we are accessing
{ i, i+1, i+2, i+3 }, if we're peeling at least a single scalar iteration
we still access possibly one too much elements.
The simplest solution would be to access { i, i+1 } only which I think
we already can do. The other solution is to peel N scalar
iterations or apply masking to not access elements in the gap if the ISA
supports that.
