This fixes bogus misalignment calculation for negative steps
since an assertion a previous comment indicated no longer holds:
/* DR_STEP(dr) is the same as -TYPE_SIZE of the scalar type,
otherwise we wouldn't be here. */
Thus the following replaces DR_STEP by -TYPE_SIZE.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk
sofar.
Richard.
2020-07-06 Richard Biener <rguent...@suse.de>
PR tree-optimization/96075
* tree-vect-data-refs.c (vect_compute_data_ref_alignment): Use
TYPE_SIZE_UNIT of the vector component type instead of DR_STEP
for the misalignment calculation for negative step.
* gcc.dg/vect/slp-46.c: New testcase.
---
gcc/testsuite/gcc.dg/vect/slp-46.c | 96 ++++++++++++++++++++++++++++++
gcc/tree-vect-data-refs.c | 2 +-
2 files changed, 97 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/vect/slp-46.c
diff --git a/gcc/testsuite/gcc.dg/vect/slp-46.c
b/gcc/testsuite/gcc.dg/vect/slp-46.c
new file mode 100644
index 00000000000..17dfa285ec1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/slp-46.c
@@ -0,0 +1,96 @@
+/* { dg-require-effective-target vect_double } */
+
+#include "tree-vect.h"
+
+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];
+ }
+}
+
+void __attribute__((noipa)) bar()
+{
+ for (int i = 0; i < 512; ++i)
+ {
+ x[2*i] = y[2*i];
+ x[2*i+1] = y[2*i];
+ }
+}
+
+void __attribute__((noipa)) baz()
+{
+ for (int i = 0; i < 512; ++i)
+ {
+ x[2*i] = y[511-i];
+ x[2*i+1] = y[511-i];
+ }
+}
+
+void __attribute__((noipa)) boo()
+{
+ for (int i = 0; i < 512; ++i)
+ {
+ x[2*i] = y[2*(511-i)];
+ x[2*i+1] = y[2*(511-i)];
+ }
+}
+
+int
+main ()
+{
+ check_vect ();
+
+ for (int i = 0; i < 1024; ++i)
+ {
+ x[i] = 0;
+ y[i] = i;
+ __asm__ volatile ("");
+ }
+
+ foo ();
+ for (int i = 0; i < 1024; ++i)
+ if (x[i] != y[i/2])
+ abort ();
+
+ for (int i = 0; i < 1024; ++i)
+ {
+ x[i] = 0;
+ __asm__ volatile ("");
+ }
+
+ bar ();
+ for (int i = 0; i < 1024; ++i)
+ if (x[i] != y[2*(i/2)])
+ abort ();
+
+ for (int i = 0; i < 1024; ++i)
+ {
+ x[i] = 0;
+ __asm__ volatile ("");
+ }
+
+ baz ();
+ for (int i = 0; i < 1024; ++i)
+ if (x[i] != y[511 - i/2])
+ abort ();
+
+ for (int i = 0; i < 1024; ++i)
+ {
+ x[i] = 0;
+ __asm__ volatile ("");
+ }
+
+ boo ();
+ for (int i = 0; i < 1024; ++i)
+ if (x[i] != y[2*(511 - i/2)])
+ abort ();
+
+ return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "vectorizing stmts using SLP" 2 "vect" }
} */
diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
index 2462276e7c2..959c2d3378f 100644
--- a/gcc/tree-vect-data-refs.c
+++ b/gcc/tree-vect-data-refs.c
@@ -1109,7 +1109,7 @@ vect_compute_data_ref_alignment (vec_info *vinfo,
dr_vec_info *dr_info)
if (tree_int_cst_sgn (drb->step) < 0)
/* PLUS because STEP is negative. */
misalignment += ((TYPE_VECTOR_SUBPARTS (vectype) - 1)
- * TREE_INT_CST_LOW (drb->step));
+ * -TREE_INT_CST_LOW (TYPE_SIZE_UNIT (TREE_TYPE
(vectype))));
unsigned int const_misalignment;
if (!known_misalignment (misalignment, vect_align_c, &const_misalignment))
--
2.26.2
