tree-optimization/105080 - make sure SCEV is available for ranger

When doing format diagnostics at -O0 we should make sure to make
SCEV available to avoid false positives due to ranges we otherwise
can trivially compute.

2022-03-28  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/105080
	* tree-ssa-strlen.cc (printf_strlen_execute): Always init
	loops and SCEV.

	* gcc.dg/pr105080.c: New testcase.

diff --git a/gcc/testsuite/gcc.dg/pr105080.c b/gcc/testsuite/gcc.dg/pr105080.c
new file mode 100644 (file)
index 0000000..77ee7ee
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr105080.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O0 -Wall" } */
+
+int main()
+{
+  char foo[3];
+  int i;
+
+  for (i = 0; i < 16; i++)
+    __builtin_snprintf(foo, sizeof(foo), "%d", i);  /* { dg-bogus "truncated" } */
+}

diff --git a/gcc/tree-ssa-strlen.cc b/gcc/tree-ssa-strlen.cc
index 112f0dc..b255636 100644 (file)
--- a/gcc/tree-ssa-strlen.cc
+++ b/gcc/tree-ssa-strlen.cc
@@ -5858,13 +5858,8 @@ printf_strlen_execute (function *fun, bool warn_only)
   strlen_optimize = !warn_only;
 
   calculate_dominance_info (CDI_DOMINATORS);
-
-  bool use_scev = optimize > 0 && flag_printf_return_value;
-  if (use_scev)
-    {
-      loop_optimizer_init (LOOPS_NORMAL);
-      scev_initialize ();
-    }
+  loop_optimizer_init (LOOPS_NORMAL);
+  scev_initialize ();
 
   gcc_assert (!strlen_to_stridx);
   if (warn_stringop_overflow || warn_stringop_truncation)
@@ -5902,11 +5897,8 @@ printf_strlen_execute (function *fun, bool warn_only)
       strlen_to_stridx = NULL;
     }
 
-  if (use_scev)
-    {
-      scev_finalize ();
-      loop_optimizer_finalize ();
-    }
+  scev_finalize ();
+  loop_optimizer_finalize ();
 
   return walker.m_cleanup_cfg ? TODO_cleanup_cfg : 0;
 }