[gcc r15-3716] tree-optimization/116768 - wrong dependence analysis

[Richard Biener via Gcc-cvs]

https://gcc.gnu.org/g:5b5a36b122e1205449f1512bf39521b669e713ef

commit r15-3716-g5b5a36b122e1205449f1512bf39521b669e713ef
Author: Richard Biener <rguent...@suse.de>
Date:   Thu Sep 19 14:58:18 2024 +0200

    tree-optimization/116768 - wrong dependence analysis
    
    The following reverts a bogus fix done for PR101009 and instead makes
    sure we get into the same_access_functions () case when computing
    the distance vector for g[1] and g[1] where the constants ended up
    having different types.  The generic code doesn't seem to handle
    loop invariant dependences.  The special case gets us both
    ( 0 ) and ( 1 ) as distance vectors while formerly we got ( 1 ),
    which the PR101009 fix changed to ( 0 ) with bad effects on other
    cases as shown in this PR.
    
            PR tree-optimization/116768
            * tree-data-ref.cc (build_classic_dist_vector_1): Revert
            PR101009 change.
            * tree-chrec.cc (eq_evolutions_p): Make sure (sizetype)1
            and (int)1 compare equal.
    
            * gcc.dg/torture/pr116768.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr116768.c | 32 ++++++++++++++++++++++++++++++++
 gcc/tree-chrec.cc                       |  4 ++--
 gcc/tree-data-ref.cc                    |  2 --
 3 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr116768.c 
b/gcc/testsuite/gcc.dg/torture/pr116768.c
new file mode 100644
index 000000000000..57b5d00e7b71
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr116768.c
@@ -0,0 +1,32 @@
+/* { dg-do run } */
+
+#define numwords 2
+
+typedef struct {
+  unsigned words[numwords];
+} Child;
+
+typedef struct {
+  Child child;
+} Parent;
+
+Parent my_or(Parent x, const Parent *y) {
+  const Child *y_child = &y->child;
+  for (int i = 0; i < numwords; i++) {
+    x.child.words[i] |= y_child->words[i];
+  }
+  return x;
+}
+
+int main() {
+  Parent bs[4];
+  __builtin_memset(bs, 0, sizeof(bs));
+
+  bs[0].child.words[0] = 1;
+  for (int i = 1; i <= 3; i++) {
+    bs[i] = my_or(bs[i], &bs[i - 1]);
+  }
+  if (bs[2].child.words[0] != 1)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/tree-chrec.cc b/gcc/tree-chrec.cc
index 8b7982a2dbe9..9b272074a2ed 100644
--- a/gcc/tree-chrec.cc
+++ b/gcc/tree-chrec.cc
@@ -1716,7 +1716,7 @@ eq_evolutions_p (const_tree chrec0, const_tree chrec1)
       || TREE_CODE (chrec0) != TREE_CODE (chrec1))
     return false;
 
-  if (chrec0 == chrec1)
+  if (operand_equal_p (chrec0, chrec1, 0))
     return true;
 
   if (! types_compatible_p (TREE_TYPE (chrec0), TREE_TYPE (chrec1)))
@@ -1743,7 +1743,7 @@ eq_evolutions_p (const_tree chrec0, const_tree chrec1)
                              TREE_OPERAND (chrec1, 0));
 
     default:
-      return operand_equal_p (chrec0, chrec1, 0);
+      return false;
     }
 }
 
diff --git a/gcc/tree-data-ref.cc b/gcc/tree-data-ref.cc
index 0f173e8803ab..de234c65e948 100644
--- a/gcc/tree-data-ref.cc
+++ b/gcc/tree-data-ref.cc
@@ -5223,8 +5223,6 @@ build_classic_dist_vector_1 (struct 
data_dependence_relation *ddr,
          non_affine_dependence_relation (ddr);
          return false;
        }
-      else
-       *init_b = true;
     }
 
   return true;