The following fixes a latent bug in vect dataref alignment analysis.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2017-03-27 Richard Biener <rguent...@suse.de>
PR tree-optimization/80170
* tree-vect-data-refs.c (vect_compute_data_ref_alignment): Make
sure DR/SCEV didnt fold in constants we do not see when looking
at the reference base alignment.
* gcc.dg/pr80170.c: New testcase.
Index: gcc/tree-vect-data-refs.c
===================================================================
--- gcc/tree-vect-data-refs.c (revision 246489)
+++ gcc/tree-vect-data-refs.c (working copy)
@@ -779,7 +779,7 @@ vect_compute_data_ref_alignment (struct
base = ref;
while (handled_component_p (base))
base = TREE_OPERAND (base, 0);
- unsigned int base_alignment;
+ unsigned int base_alignment = 0;
unsigned HOST_WIDE_INT base_bitpos;
get_object_alignment_1 (base, &base_alignment, &base_bitpos);
/* As data-ref analysis strips the MEM_REF down to its base operand
@@ -788,8 +788,17 @@ vect_compute_data_ref_alignment (struct
DR_BASE_ADDRESS. */
if (TREE_CODE (base) == MEM_REF)
{
- base_bitpos -= mem_ref_offset (base).to_short_addr () * BITS_PER_UNIT;
- base_bitpos &= (base_alignment - 1);
+ /* Note all this only works if DR_BASE_ADDRESS is the same as
+ MEM_REF operand zero, otherwise DR/SCEV analysis might have factored
+ in other offsets. We need to rework DR to compute the alingment
+ of DR_BASE_ADDRESS as long as all information is still available. */
+ if (operand_equal_p (TREE_OPERAND (base, 0), base_addr, 0))
+ {
+ base_bitpos -= mem_ref_offset (base).to_short_addr () * BITS_PER_UNIT;
+ base_bitpos &= (base_alignment - 1);
+ }
+ else
+ base_bitpos = BITS_PER_UNIT;
}
if (base_bitpos != 0)
base_alignment = base_bitpos & -base_bitpos;
Index: gcc/testsuite/gcc.dg/pr80170.c
===================================================================
--- gcc/testsuite/gcc.dg/pr80170.c (nonexistent)
+++ gcc/testsuite/gcc.dg/pr80170.c (working copy)
@@ -0,0 +1,42 @@
+/* { dg-do run } */
+/* { dg-options "-fgimple -O2 -ftree-slp-vectorize" } */
+
+struct A
+{
+ void * a;
+ void * b;
+};
+
+struct __attribute__((aligned(16))) B
+{
+ void * pad;
+ void * misaligned;
+ void * pad2;
+
+ struct A a;
+};
+
+__attribute__((noclone, noinline))
+void __GIMPLE (startwith("slp"))
+NullB (void * misalignedPtr)
+{
+ struct B * b;
+
+ bb_2:
+#if __SIZEOF_LONG__ == 8
+ b_2 = misalignedPtr_1(D) + 18446744073709551608ul;
+#else
+ b_2 = misalignedPtr_1(D) + 4294967292ul;
+#endif
+ __MEM <struct B> (b_2).a.a = _Literal (void *) 0;
+ __MEM <struct B> (b_2).a.b = _Literal (void *) 0;
+ return;
+
+}
+
+int main()
+{
+ struct B b;
+ NullB (&b.misaligned);
+ return 0;
+}
