[gcc r17-2485] testsuite: Add regression test for PR81549

https://gcc.gnu.org/g:bbc7fd5ae68069863b77a9d614a9aa82a4079e58

commit r17-2485-gbbc7fd5ae68069863b77a9d614a9aa82a4079e58
Author: Naveen <[email protected]>
Date:   Fri Jul 17 04:13:10 2026 -0700

    testsuite: Add regression test for PR81549
    
    The testcase from PR tree-optimization/81549 is already optimized on
    current trunk by the existing loop-PHI final-value replacement code.
    Add the testcase to preserve coverage for the delayed loop-carried value
    and verify that the final stores and return value are folded to constants.
    
    gcc/testsuite/ChangeLog:
    
            PR tree-optimization/81549
            * gcc.dg/tree-ssa/pr81549.c: New test.
            * gcc.dg/tree-ssa/pr81549-2.c: New test.
    
    Signed-off-by: Naveen <[email protected]>

Diff:
---
 gcc/testsuite/gcc.dg/tree-ssa/pr81549-2.c | 46 +++++++++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr81549.c   | 28 +++++++++++++++++++
 2 files changed, 74 insertions(+)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr81549-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr81549-2.c
new file mode 100644
index 000000000000..236ef0cabd02
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr81549-2.c
@@ -0,0 +1,46 @@
+/* PR tree-optimization/81549 */
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+int a[4];
+
+__attribute__((noipa)) int
+f (int n)
+{
+  int t0 = a[0];
+  int t1 = a[1];
+
+  for (int i = 0; i < n; ++i)
+    {
+      t0 = t1;
+      t1 = 2;
+    }
+
+  return t0;
+}
+
+__attribute__((noipa)) int
+g (void)
+{
+  int t0 = a[0];
+  int t1 = a[1];
+
+  for (int i = 0; i < 1; ++i)
+    {
+      t0 = t1;
+      t1 = 2;
+    }
+
+  return t0;
+}
+
+int
+main (void)
+{
+  a[0] = 11;
+  a[1] = 22;
+
+  if (f (0) != 11 || f (1) != 22 || f (2) != 2 || g () != 22)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr81549.c b/gcc/testsuite/gcc.dg/tree-ssa/pr81549.c
new file mode 100644
index 000000000000..fdbe79ab1c55
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr81549.c
@@ -0,0 +1,28 @@
+/* PR tree-optimization/81549 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-sccp-details -fdump-tree-optimized" } */
+
+int a[10000];
+
+int
+f (void)
+{
+  int t0 = a[0];
+  int t1 = a[1];
+
+  for (int i = 0; i < 100; ++i)
+    {
+      a[i] = 1;
+      t0 = t1;
+      t1 = 2;
+    }
+
+  a[100] = t0;
+  a[101] = t1;
+  return t0 + t1;
+}
+
+/* { dg-final { scan-tree-dump-times "with expr: 2" 1 "sccp" } } */
+/* { dg-final { scan-tree-dump {a\[100\] = 2;} "sccp" } } */
+/* { dg-final { scan-tree-dump {a\[101\] = 2;} "sccp" } } */
+/* { dg-final { scan-tree-dump "return 4;" "optimized" } } */