re PR tree-optimization/63445 (request: make -Wstrict-overflow avoid a class of false...

2014-10-09  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/63445
	* tree-vrp.c (simplify_cond_using_ranges): Only warn about
	overflow for non-equality compares.

	* gcc.dg/Wstrict-overflow-26.c: New testcase.

From-SVN: r216028

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 85bc361..b8b9f30 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2014-10-09  Richard Biener  <rguenther@suse.de>
+
+       PR tree-optimization/63445
+       * tree-vrp.c (simplify_cond_using_ranges): Only warn about
+       overflow for non-equality compares.
+
 2014-10-09  Uros Bizjak  <ubizjak@gmail.com>
 
        PR rtl-optimization/57003

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index b282bc7..a8870ea 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2014-10-09  Richard Biener  <rguenther@suse.de>
+
+       PR tree-optimization/63445
+       * gcc.dg/Wstrict-overflow-26.c: New testcase.
+
 2014-10-08  Pat Haugen  <pthaugen@us.ibm.com>
 
        * gcc.dg/vmx/3c-01a.c: Add default options from vmx.exp.

diff --git a/gcc/testsuite/gcc.dg/Wstrict-overflow-26.c b/gcc/testsuite/gcc.dg/Wstrict-overflow-26.c
new file mode 100644 (file)
index 0000000..ef805b5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wstrict-overflow-26.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -Wstrict-overflow" } */
+
+int
+f (int i, int j)
+{
+  unsigned int c = 0;                                                          
+  if (i < j)
+    {
+      unsigned int n = j - i;
+      unsigned int i;
+      for (i = 0; i < n; i++) /* { dg-bogus "signed overflow" } */
+       c++;
+    }
+  return c;
+}

diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 011db78..7ca0528 100644 (file)
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -9189,8 +9189,9 @@ simplify_cond_using_ranges (gimple stmt)
              /* If the range overflowed and the user has asked for warnings
                 when strict overflow semantics were used to optimize code,
                 issue an appropriate warning.  */
-             if ((is_negative_overflow_infinity (vr->min)
-                  || is_positive_overflow_infinity (vr->max))
+             if (cond_code != EQ_EXPR && cond_code != NE_EXPR
+                 && (is_negative_overflow_infinity (vr->min)
+                     || is_positive_overflow_infinity (vr->max))
                  && issue_strict_overflow_warning (WARN_STRICT_OVERFLOW_CONDITIONAL))
                {
                  location_t location;