Add missing unit dependence vector in data dependence analysis

Current data dependence analysis misses unit distant vector if DRs in
DDR have the same invariant access functions.  This adds the vector as
the constant access function case.

2020-05-13  Bin Cheng  <bin.cheng@linux.alibaba.com>
PR tree-optimization/94969

gcc/
    * tree-data-dependence.c (constant_access_functions): Rename to...
    (invariant_access_functions): ...this.  Add parameter.  Check for
    invariant access function, rather than constant.
    (build_classic_dist_vector): Call above function.
    * tree-loop-distribution.c (pg_add_dependence_edges): Add comment.

gcc/testsuite/
    * gcc.dg/tree-ssa/pr94969.c: New test.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a7c8adecb9d10b3a85b7ed7b3b6ebe63da50eb0c..4234a72432c6f1c45a55b48e7b1104f7f878b798 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2020-05-13  Bin Cheng  <bin.cheng@linux.alibaba.com>
+
+       PR tree-optimization/94969
+       * tree-data-dependence.c (constant_access_functions): Rename to...
+       (invariant_access_functions): ...this.  Add parameter.  Check for
+       invariant access function, rather than constant.
+       (build_classic_dist_vector): Call above function.
+       * tree-loop-distribution.c (pg_add_dependence_edges): Add comment.
+
 2020-05-13  Hongtao Liu  <hongtao.liu@intel.com>
 
        PR target/94118

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9ad48bad03178787e3d98a77aac26fc774d73d4b..5a4215bbe46e2d84539fb3d5924978c5586b6304 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-13  Bin Cheng  <bin.cheng@linux.alibaba.com>
+
+       PR tree-optimization/94969
+       * gcc.dg/tree-ssa/pr94969.c: New test.
+
 2020-05-12  Craig Blackmore  <craig.blackmore@embecosm.com>
 
        * gcc.target/riscv/shorten-memrefs-1.c: New test.

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr94969.c b/gcc/testsuite/gcc.dg/tree-ssa/pr94969.c
new file mode 100644 (file)
index 0000000..056b015
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr94969.c
@@ -0,0 +1,28 @@
+/* PR tree-optimization/52267 */
+/* { dg-do run } */
+/* { dg-options "-O3 -fdump-tree-ldist-details" } */
+
+int a = 0, b = 0, c = 0;
+struct S {
+  signed m : 7;
+  signed e : 2;
+};
+struct S f[2] = {{0, 0}, {0, 0}};
+struct S g = {0, 0};
+
+void __attribute__((noinline))
+k()
+{
+  for (; c <= 1; c++) {
+    f[b] = g;
+    f[b].e ^= 1;
+  }
+}
+int main()
+{
+  k();
+  if (f[b].e != 1)
+    __builtin_abort ();
+}
+
+/* { dg-final { scan-tree-dump-not "ldist" "Loop 1 distributed: split to 3 loops"} } */

diff --git a/gcc/tree-data-ref.c b/gcc/tree-data-ref.c
index 851225e117176b33dbcd5448f02569103df2d572..5505ba46778501b25862c064798e3cecc8212477 100644 (file)
--- a/gcc/tree-data-ref.c
+++ b/gcc/tree-data-ref.c
@@ -4821,17 +4821,19 @@ build_classic_dist_vector_1 (struct data_dependence_relation *ddr,
   return true;
 }
 
-/* Return true when the DDR contains only constant access functions.  */
+/* Return true when the DDR contains only invariant access functions wrto. loop
+   number LNUM.  */
 
 static bool
-constant_access_functions (const struct data_dependence_relation *ddr)
+invariant_access_functions (const struct data_dependence_relation *ddr,
+                           int lnum)
 {
   unsigned i;
   subscript *sub;
 
   FOR_EACH_VEC_ELT (DDR_SUBSCRIPTS (ddr), i, sub)
-    if (!evolution_function_is_constant_p (SUB_ACCESS_FN (sub, 0))
-       || !evolution_function_is_constant_p (SUB_ACCESS_FN (sub, 1)))
+    if (!evolution_function_is_invariant_p (SUB_ACCESS_FN (sub, 0), lnum)
+       || !evolution_function_is_invariant_p (SUB_ACCESS_FN (sub, 1), lnum))
       return false;
 
   return true;
@@ -5030,7 +5032,7 @@ build_classic_dist_vector (struct data_dependence_relation *ddr,
       dist_v = lambda_vector_new (DDR_NB_LOOPS (ddr));
       save_dist_v (ddr, dist_v);
 
-      if (constant_access_functions (ddr))
+      if (invariant_access_functions (ddr, loop_nest->num))
        add_distance_for_zero_overlaps (ddr);
 
       if (DDR_NB_LOOPS (ddr) > 1)

diff --git a/gcc/tree-loop-distribution.c b/gcc/tree-loop-distribution.c
index 4442321533286ed78c2743532456c51229d6288b..b122c3964a093d33ce2657588186dfb79e04d7b2 100644 (file)
--- a/gcc/tree-loop-distribution.c
+++ b/gcc/tree-loop-distribution.c
@@ -2080,7 +2080,8 @@ loop_distribution::pg_add_dependence_edges (struct graph *rdg, int dir,
                this_dir = -this_dir;
 
              /* Known dependences can still be unordered througout the
-                iteration space, see gcc.dg/tree-ssa/ldist-16.c.  */
+                iteration space, see gcc.dg/tree-ssa/ldist-16.c and
+                gcc.dg/tree-ssa/pr94969.c.  */
              if (DDR_NUM_DIST_VECTS (ddr) != 1)
                this_dir = 2;
              /* If the overlap is exact preserve stmt order.  */