re PR c++/71537 (GCC rejects consetxpr boolean conversions and comparisons on the result of pointer arithmetic.)

	PR c++/71537
	* fold-const-call.c (fold_const_call): Handle
	CFN_BUILT_IN_{INDEX,STRCHR,RINDEX,STRRCHR}.

	* g++.dg/cpp0x/constexpr-strchr.C: New test.

From-SVN: r243284

4 files changed, 59 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4e70e27..029dbdc 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,9 @@
 2016-12-06  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/71537
+	* fold-const-call.c (fold_const_call): Handle
+	CFN_BUILT_IN_{INDEX,STRCHR,RINDEX,STRRCHR}.
+
 	PR tree-optimization/78675
 	* tree-vect-loop.c (vectorizable_live_operation): For
 	VECTOR_BOOLEAN_TYPE_P vectype use integral type with bitsize precision
diff --git a/gcc/fold-const-call.c b/gcc/fold-const-call.c
index e2d0eaf..439988d 100644
--- a/gcc/fold-const-call.c
+++ b/gcc/fold-const-call.c
@@ -1383,6 +1383,7 @@ tree
 fold_const_call (combined_fn fn, tree type, tree arg0, tree arg1)
 {
   const char *p0, *p1;
+  char c;
   switch (fn)
     {
     case CFN_BUILT_IN_STRSPN:
@@ -1409,6 +1410,30 @@ fold_const_call (combined_fn fn, tree type, tree arg0, tree arg1)
 	}
       return NULL_TREE;
 
+    case CFN_BUILT_IN_INDEX:
+    case CFN_BUILT_IN_STRCHR:
+      if ((p0 = c_getstr (arg0)) && target_char_cst_p (arg1, &c))
+	{
+	  const char *r = strchr (p0, c);
+	  if (r == NULL)
+	    return build_int_cst (type, 0);
+	  return fold_convert (type,
+			       fold_build_pointer_plus_hwi (arg0, r - p0));
+	}
+      return NULL_TREE;
+
+    case CFN_BUILT_IN_RINDEX:
+    case CFN_BUILT_IN_STRRCHR:
+      if ((p0 = c_getstr (arg0)) && target_char_cst_p (arg1, &c))
+	{
+	  const char *r = strrchr (p0, c);
+	  if (r == NULL)
+	    return build_int_cst (type, 0);
+	  return fold_convert (type,
+			       fold_build_pointer_plus_hwi (arg0, r - p0));
+	}
+      return NULL_TREE;
+
     default:
       return fold_const_call_1 (fn, type, arg0, arg1);
     }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 35f10fe..e6dfcdc 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2016-12-06  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/71537
+	* g++.dg/cpp0x/constexpr-strchr.C: New test.
+
 	PR tree-optimization/78675
 	* gcc.c-torture/execute/pr78675.c: New test.
 	* gcc.target/i386/pr78675-1.c: New test.
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-strchr.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-strchr.C
new file mode 100644
index 0000000..c44d8a2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-strchr.C
@@ -0,0 +1,27 @@
+// { dg-do compile { target c++11 } }
+
+constexpr const char *f1 (const char *p, int q) { return __builtin_strchr (p, q); }
+constexpr const char *f2 (const char *p, int q) { return __builtin_index (p, q); }
+constexpr const char *f3 (const char *p, int q) { return __builtin_strrchr (p, q); }
+constexpr const char *f4 (const char *p, int q) { return __builtin_rindex (p, q); }
+constexpr const char a[] = "abcdefedcba";
+static_assert (f1 ("abcde", 'f') == nullptr, "");
+static_assert (f1 (a, 'g') == nullptr, "");
+static_assert (f1 (a, 'f') == a + 5, "");
+static_assert (f1 (a, 'c') == a + 2, "");
+static_assert (f1 (a, '\0') == a + 11, "");
+static_assert (f2 ("abcde", 'f') == nullptr, "");
+static_assert (f2 (a, 'g') == nullptr, "");
+static_assert (f2 (a, 'f') == a + 5, "");
+static_assert (f2 (a, 'c') == a + 2, "");
+static_assert (f2 (a, '\0') == a + 11, "");
+static_assert (f3 ("abcde", 'f') == nullptr, "");
+static_assert (f3 (a, 'g') == nullptr, "");
+static_assert (f3 (a, 'f') == a + 5, "");
+static_assert (f3 (a, 'c') == a + 8, "");
+static_assert (f3 (a, '\0') == a + 11, "");
+static_assert (f4 ("abcde", 'f') == nullptr, "");
+static_assert (f4 (a, 'g') == nullptr, "");
+static_assert (f4 (a, 'f') == a + 5, "");
+static_assert (f4 (a, 'c') == a + 8, "");
+static_assert (f4 (a, '\0') == a + 11, "");