[PATCH] PR tree-optimization/107570 - Reset SCEV after folding in VRP.

[Andrew MacLeod <amacleod@redhat.com>]

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We can reset SCEV after we fold, then SCEVs cache shouldn't have 
anything in it when we go to remove ssa-names in remove_unreachable().

We were resetting it later sometimes if we were processing the array 
bounds warning, so I removed that call and just always reset it now.

Bootstraps on x86_64-pc-linux-gnu. Testing running. Assuming no 
regressions,  OK for trunk?

Andrew

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From 450b058445ffb0a1ffbdec08732d4267f03a8ce5 Mon Sep 17 00:00:00 2001
From: Andrew MacLeod <amacleod@redhat.com>
Date: Wed, 1 Feb 2023 11:46:18 -0500
Subject: [PATCH] Reset SCEV after folding in VRP.

SCEV needs to be reset to processing array bounds in VRP, but it should
also be reset before trying to remove unreachable globals so it's cache
doesn't cause issues.

	PR tree-optimization/107570
	gcc/
	* tree-vrp.cc (execute_ranger_vrp): Reset SCEV after folding.

	gcc/testsuite/
	gcc.dg/pr107570.c: New.
---
 gcc/testsuite/gcc.dg/pr107570.c | 25 +++++++++++++++++++++++++
 gcc/tree-vrp.cc                 |  6 +++++-
 2 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr107570.c

diff --git a/gcc/testsuite/gcc.dg/pr107570.c b/gcc/testsuite/gcc.dg/pr107570.c
new file mode 100644
index 00000000000..ba5b535a867
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr107570.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+
+long int n;
+
+void
+foo (int *p, int x)
+{
+  for (;;)
+    {
+      for (*p = 0; *p < 1; ++*p)
+        {
+          n += *p < 0;
+          if (n < x)
+            {
+              while (x < 1)
+                ++x;
+
+              __builtin_unreachable ();
+            }
+        }
+
+      p = &x;
+    }
+}
diff --git a/gcc/tree-vrp.cc b/gcc/tree-vrp.cc
index 3c431760a16..0b69374adba 100644
--- a/gcc/tree-vrp.cc
+++ b/gcc/tree-vrp.cc
@@ -1096,6 +1096,11 @@ execute_ranger_vrp (struct function *fun, bool warn_array_bounds_p,
   gimple_ranger *ranger = enable_ranger (fun, false);
   rvrp_folder folder (ranger);
   folder.substitute_and_fold ();
+
+  // SCEV needs to be reset for array bounds, and we do not wish to trigger
+  // any SCEV lookups when removing unreachable globals, so reset it here.
+  scev_reset ();
+
   // Remove tagged builtin-unreachable and maybe update globals.
   folder.m_unreachable.remove_and_update_globals (final_p);
   if (dump_file && (dump_flags & TDF_DETAILS))
@@ -1116,7 +1121,6 @@ execute_ranger_vrp (struct function *fun, bool warn_array_bounds_p,
 	    else
 	      e->flags |= EDGE_EXECUTABLE;
 	}
-      scev_reset ();
       array_bounds_checker array_checker (fun, ranger);
       array_checker.check ();
     }
-- 
2.39.0