When the whole shift is invariant but the shift amount needs
to be converted and a vector shift used we can mess up placement
of vector stmts because we do not make SLP scheduling aware of
the need to insert code for it. The following mitigates this
by more conservative placement of such code in vectorizable_shift.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/119640
* tree-vect-stmts.cc (vectorizable_shift): Always insert code
for one of our SLP operands before the code for the vector
shift itself.
* gcc.dg/vect/pr119640.c: New testcase.
---
gcc/testsuite/gcc.dg/vect/pr119640.c | 17 +++++++++++++++++
gcc/tree-vect-stmts.cc | 11 +++++++----
2 files changed, 24 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/vect/pr119640.c
diff --git a/gcc/testsuite/gcc.dg/vect/pr119640.c
b/gcc/testsuite/gcc.dg/vect/pr119640.c
new file mode 100644
index 00000000000..8872817ac31
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr119640.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-funswitch-loops" } */
+
+int save, mask_nbits;
+
+void execute(long imm)
+{
+ long shift = 0;
+ int destReg[4];
+ for (unsigned i = 0; i < 4; i++)
+ {
+ if (imm)
+ shift = 1ULL << mask_nbits;
+ destReg[i] = shift;
+ save = destReg[0];
+ }
+}
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index 37a54bf5000..ffca2ab50d5 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -6758,13 +6758,16 @@ vectorizable_shift (vec_info *vinfo,
{
if (was_scalar_shift_arg)
{
- /* If the argument was the same in all lanes create
- the correctly typed vector shift amount directly. */
+ /* If the argument was the same in all lanes create the
+ correctly typed vector shift amount directly. Note
+ we made SLP scheduling think we use the original scalars,
+ so place the compensation code next to the shift which
+ is conservative. See PR119640 where it otherwise breaks. */
op1 = fold_convert (TREE_TYPE (vectype), op1);
op1 = vect_init_vector (vinfo, stmt_info, op1, TREE_TYPE (vectype),
- !loop_vinfo ? gsi : NULL);
+ gsi);
vec_oprnd1 = vect_init_vector (vinfo, stmt_info, op1, vectype,
- !loop_vinfo ? gsi : NULL);
+ gsi);
vec_oprnds1.create (slp_node->vec_stmts_size);
for (k = 0; k < slp_node->vec_stmts_size; k++)
vec_oprnds1.quick_push (vec_oprnd1);
--
2.43.0
