Hi!
The following testcase ICEs because disabling of DCE means there are dead
stmts in the loop (though, in theory they could become dead only shortly
before if-conv through some optimization), ifcvt which goes through all
stmts in the loop if-converts them into .COND_DIV etc. internal fn calls
in the copy of the loop meant for vectorization only, the loop is
successfully vectorized but the particular .COND_* call is not because
it isn't a live statement and the scalar .COND_* remains in the IL until
expansion where it ICEs because these ifns only support vectors and not
scalars.
These ifns are similar to .MASK_{LOAD,STORE} in this behavior.
One possible fix could be to expand scalar versions of them during
expansion, basically undoing what if-conv did to create them, i.e.
expand them as the lhs = else; if (mask) { lhs = statement; } or so.
For .MASK_LOAD we have code to replace them in vect_transform_loop already
though (not needed for .MASK_STORE, as stores should be always live
and thus always vectorized), so this patch instead replaces .COND_*
similarly to .MASK_LOAD in that loop, with the small difference
that lhs = .MASK_LOAD (...); is replaced by lhs = 0; while
lhs = .COND_* (..., else_arg); is replaced by lhs = else_arg.
The statement must be dead, otherwise it would be vectorized, so I think
it is not a big deal we don't turn it back into multiple basic blocks etc.
(and it might be not possible to do that at that point).
Bootstrapped/regtested on {x86_64,i686,aarch64}-linux, ok for trunk?
2021-04-16 Jakub Jelinek <ja...@redhat.com>
PR target/99767
* tree-vect-loop.c (vect_transform_loop): Don't remove just
dead scalar .MASK_LOAD calls, but also dead .COND_* calls - replace
them by their last argument.
* gcc.target/aarch64/pr99767.c: New test.
--- gcc/tree-vect-loop.c.jj 2021-04-07 12:35:13.000000000 +0200
+++ gcc/tree-vect-loop.c 2021-04-15 17:21:58.750101894 +0200
@@ -9676,7 +9676,10 @@ vect_transform_loop (loop_vec_info loop_
!gsi_end_p (gsi); gsi_next (&gsi))
{
gcall *call = dyn_cast <gcall *> (gsi_stmt (gsi));
- if (call && gimple_call_internal_p (call, IFN_MASK_LOAD))
+ if (!call || !gimple_call_internal_p (call))
+ continue;
+ internal_fn ifn = gimple_call_internal_fn (call);
+ if (ifn == IFN_MASK_LOAD)
{
tree lhs = gimple_get_lhs (call);
if (!VECTOR_TYPE_P (TREE_TYPE (lhs)))
@@ -9686,6 +9689,17 @@ vect_transform_loop (loop_vec_info loop_
gsi_replace (&gsi, new_stmt, true);
}
}
+ else if (conditional_internal_fn_code (ifn) != ERROR_MARK)
+ {
+ tree lhs = gimple_get_lhs (call);
+ if (!VECTOR_TYPE_P (TREE_TYPE (lhs)))
+ {
+ tree else_arg
+ = gimple_call_arg (call, gimple_call_num_args (call) - 1);
+ gimple *new_stmt = gimple_build_assign (lhs, else_arg);
+ gsi_replace (&gsi, new_stmt, true);
+ }
+ }
}
} /* BBs in loop */
--- gcc/testsuite/gcc.target/aarch64/pr99767.c.jj 2021-04-15
17:28:10.466928380 +0200
+++ gcc/testsuite/gcc.target/aarch64/pr99767.c 2021-04-15 17:28:45.653533566
+0200
@@ -0,0 +1,16 @@
+/* PR target/99767 */
+/* { dg-do compile } */
+/* { dg-options " -O1 -fopenmp-simd -fno-tree-dce -march=armv8-a+sve" } */
+
+int a[1024], b[1024];
+
+void
+foo (void)
+{
+ #pragma omp simd
+ for (int i = 0; i < 1024; i++)
+ if (b[i] > 23) {
+ a[i] = b[i] + 1;
+ int v = 1 / 0; /* { dg-warning "division by zero" } */
+ }
+}
Jakub
