[gcc(refs/vendors/ibm/heads/gcc-10-branch)] Add missing unit dependence vector in data dependence analysis

[Peter Bergner]

https://gcc.gnu.org/g:63c00a0c6543ce6d55e0ebc97ddbc1d36fb1289c

commit 63c00a0c6543ce6d55e0ebc97ddbc1d36fb1289c
Author: Bin Cheng <bin.cheng@linux.alibaba.com>
Date:   Sat Jun 20 14:24:31 2020 +0800

    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.
    
    Also fix typo in testcase.
    
    Backport from master.
    
    2020-06-20  Bin Cheng  <bin.cheng@linux.alibaba.com>
    
    gcc/
            PR tree-optimization/94969
            * tree-data-ref.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/
            PR tree-optimization/94969
            * gcc.dg/tree-ssa/pr94969.c: New test.
    
    2020-06-20  Jakub Jelinek  <jakub@redhat.com>
    
    gcc/testsuite/
            PR tree-optimization/95110
            * gcc.dg/tree-ssa/pr94969.c: Swap scan-tree-dump-not arguments.

Diff:
---
 gcc/testsuite/gcc.dg/tree-ssa/pr94969.c | 28 ++++++++++++++++++++++++++++
 gcc/tree-data-ref.c                     | 12 +++++++-----
 gcc/tree-loop-distribution.c            |  3 ++-
 3 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr94969.c b/gcc/testsuite/gcc.dg/tree-ssa/pr94969.c
new file mode 100644
index 00000000000..f15046122ff
--- /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 "Loop 1 distributed: split to 3 loops" "ldist" } } */
diff --git a/gcc/tree-data-ref.c b/gcc/tree-data-ref.c
index 851225e1171..5505ba46778 100644
--- 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 44423215332..b122c3964a0 100644
--- 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.  */