tree-vect-data-refs.c (vect_analyze_data_ref_dependence): Allow read-after-read dependencies in basic block SLP.

        * tree-vect-data-refs.c (vect_analyze_data_ref_dependence): Allow
        read-after-read dependencies in basic block SLP.

From-SVN: r178880

4 files changed, 71 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index dc1245e..7c44c12 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2011-09-15  Ira Rosen  <ira.rosen@linaro.org>
+
+	* tree-vect-data-refs.c (vect_analyze_data_ref_dependence): Allow
+	read-after-read dependencies in basic block SLP.
+
 2011-09-14  Richard Sandiford  <rdsandiford@googlemail.com>
 
 	* config/sparc/sparc.md: Use match_test rather than eq/ne symbol_ref
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 28d1102..71e748d 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2011-09-15  Ira Rosen  <ira.rosen@linaro.org>
+
+	* gcc.dg/vect/bb-slp-25.c: New.
+
 2011-09-14  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/50391
diff --git a/gcc/testsuite/gcc.dg/vect/bb-slp-25.c b/gcc/testsuite/gcc.dg/vect/bb-slp-25.c
new file mode 100644
index 0000000..6834960
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/bb-slp-25.c
@@ -0,0 +1,57 @@
+/* { dg-require-effective-target vect_int } */
+
+#include <stdarg.h>
+#include "tree-vect.h"
+
+#define A 3
+#define B 4
+#define N 256
+
+short src[N], dst[N];
+
+void foo (short * __restrict dst, short * __restrict src, int h, int stride)
+{
+  int i;
+  h /= 16;
+  for (i = 0; i < h; i++)
+    {
+      dst[0] += A*src[0] + src[stride];
+      dst[1] += A*src[1] + src[1+stride];
+      dst[2] += A*src[2] + src[2+stride];
+      dst[3] += A*src[3] + src[3+stride];
+      dst[4] += A*src[4] + src[4+stride];
+      dst[5] += A*src[5] + src[5+stride];
+      dst[6] += A*src[6] + src[6+stride];
+      dst[7] += A*src[7] + src[7+stride];
+      dst += 8;
+      src += 8;
+   }
+}
+
+
+int main (void)
+{
+  int i;
+
+  check_vect ();
+
+  for (i = 0; i < N; i++)
+    {
+       dst[i] = 0;
+       src[i] = i;
+    }
+
+  foo (dst, src, N, 8);
+
+  for (i = 0; i < N/2; i++)
+    {
+      if (dst[i] != A * i + i + 8)
+        abort ();
+    }
+
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "basic block vectorized using SLP" 1 "slp" { target vect_element_align } } } */
+/* { dg-final { cleanup-tree-dump "slp" } } */
+
diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
index e4d32e9..33ccf34 100644
--- a/gcc/tree-vect-data-refs.c
+++ b/gcc/tree-vect-data-refs.c
@@ -607,6 +607,11 @@ vect_analyze_data_ref_dependence (struct data_dependence_relation *ddr,
       if (vect_check_interleaving (dra, drb))
          return false;
 
+      /* Read-read is OK (we need this check here, after checking for
+         interleaving).  */
+      if (DR_IS_READ (dra) && DR_IS_READ (drb))
+        return false;
+
       if (vect_print_dump_info (REPORT_DR_DETAILS))
         {
           fprintf (vect_dump, "can't determine dependence between ");