[gcc r13-6132] reassoc: Fold some statements [PR108819]

[Jakub Jelinek <jakub@gcc.gnu.org>]

https://gcc.gnu.org/g:32b5875c911f80d551d006d7473e6f1f8705857a

commit r13-6132-g32b5875c911f80d551d006d7473e6f1f8705857a
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Feb 18 12:40:49 2023 +0100

    reassoc: Fold some statements [PR108819]
    
    This spot in update_ops can replace one or both of the assign operands with
    constants, creating 1 & 1 and similar expressions which can confuse later
    passes until they are folded.  Rather than folding both constants by hand
    and also handling swapping of operands for commutative ops if the first one
    is constant and second one is not, the following patch just uses
    fold_stmt_inplace to do that.  I think we shouldn't fold more than the
    single statement because that could screw up the rest of the pass, we'd have
    to mark all those with uids, visited and the like.
    
    2023-02-18  Jakub Jelinek  <jakub@redhat.com>
    
            PR tree-optimization/108819
            * tree-ssa-reassoc.cc (update_ops): Fold new stmt in place.
    
            * gcc.dg/pr108819.c: New test.

Diff:
---
 gcc/testsuite/gcc.dg/pr108819.c | 19 +++++++++++++++++++
 gcc/tree-ssa-reassoc.cc         |  3 +++
 2 files changed, 22 insertions(+)

diff --git a/gcc/testsuite/gcc.dg/pr108819.c b/gcc/testsuite/gcc.dg/pr108819.c
new file mode 100644
index 00000000000..28fa558b260
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr108819.c
@@ -0,0 +1,19 @@
+/* PR tree-optimization/108819 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -fno-tree-ccp -fno-tree-forwprop" } */
+
+int a, b;
+
+int
+main ()
+{
+  int d = 1;
+  for (; b; b++)
+    if (a < 1)
+      while (d <= a && a <= 0UL)
+	{
+	  int *e = &d;
+	  *e = 0;
+	}
+  return 0;
+}
diff --git a/gcc/tree-ssa-reassoc.cc b/gcc/tree-ssa-reassoc.cc
index f163612f140..8fd22591f55 100644
--- a/gcc/tree-ssa-reassoc.cc
+++ b/gcc/tree-ssa-reassoc.cc
@@ -4687,6 +4687,9 @@ update_ops (tree var, enum tree_code code, const vec<operand_entry *> &ops,
       gimple_set_uid (g, gimple_uid (stmt));
       gimple_set_visited (g, true);
       gsi_insert_before (&gsi, g, GSI_SAME_STMT);
+      gimple_stmt_iterator gsi2 = gsi_for_stmt (g);
+      if (fold_stmt_inplace (&gsi2))
+	update_stmt (g);
     }
   return var;
 }