diff mbox

Readd memchr constant folding (PR c++/71537)

Message ID 20161205165728.GP3541@tucnak.redhat.com
State New
Headers show

Commit Message

Jakub Jelinek Dec. 5, 2016, 4:57 p.m. UTC 
Hi!

The slightly less recent but also post-6 changes to move memchr
folding from builtins.c to gimple-fold.c and fold-const-call.c also broke
the constexpr handling, it now only constant folds calls that return NULL,
while previously it also handled returning first argument + constant offset.

This patch moves the misplaced memchr handling from fold_const_call_1 to
fold_const_call where similar functions are already handled, fixes
formatting etc. and also handles the case when argument + constant offset
should be returned.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2016-12-05  Jakub Jelinek  <jakub@redhat.com>

	* fold-const-call.c (fold_const_call_1): Remove memchr handling here.
	(fold_const_call) <case CFN_BUILT_IN_STRNCMP,
	case CFN_BUILT_IN_STRNCASECMP>: Formatting improvements.
	(fold_const_call) <case CFN_BUILT_IN_MEMCMP>: Likewise.  If s2 is 0
	and arguments have no side-effects, return 0.
	(fold_const_call): Handle CFN_BUILT_IN_MEMCHR.

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


	Jakub

Comments

Jeff Law Dec. 5, 2016, 5:59 p.m. UTC | #1 
On 12/05/2016 09:57 AM, Jakub Jelinek wrote:
> Hi!
>
> The slightly less recent but also post-6 changes to move memchr
> folding from builtins.c to gimple-fold.c and fold-const-call.c also broke
> the constexpr handling, it now only constant folds calls that return NULL,
> while previously it also handled returning first argument + constant offset.
>
> This patch moves the misplaced memchr handling from fold_const_call_1 to
> fold_const_call where similar functions are already handled, fixes
> formatting etc. and also handles the case when argument + constant offset
> should be returned.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2016-12-05  Jakub Jelinek  <jakub@redhat.com>
>
> 	* fold-const-call.c (fold_const_call_1): Remove memchr handling here.
> 	(fold_const_call) <case CFN_BUILT_IN_STRNCMP,
> 	case CFN_BUILT_IN_STRNCASECMP>: Formatting improvements.
> 	(fold_const_call) <case CFN_BUILT_IN_MEMCMP>: Likewise.  If s2 is 0
> 	and arguments have no side-effects, return 0.
> 	(fold_const_call): Handle CFN_BUILT_IN_MEMCHR.
>
> 	* g++.dg/cpp0x/constexpr-memchr.C: New test.
OK.
jeff
diff mbox

Patch

--- gcc/fold-const-call.c.jj	2016-12-05 12:53:38.000000000 +0100
+++ gcc/fold-const-call.c	2016-12-05 14:25:13.075687677 +0100
@@ -1491,36 +1491,6 @@  fold_const_call_1 (combined_fn fn, tree
       return NULL_TREE;
     }
 
-  switch (fn)
-    {
-    case CFN_BUILT_IN_MEMCHR:
-      {
-	char c;
-	if (integer_zerop (arg2)
-	    && !TREE_SIDE_EFFECTS (arg0)
-	    && !TREE_SIDE_EFFECTS (arg1))
-	  return build_int_cst (type, 0);
-
-	if (!tree_fits_uhwi_p (arg2) || !target_char_cst_p (arg1, &c))
-	  return NULL_TREE;
-
-	unsigned HOST_WIDE_INT length = tree_to_uhwi (arg2);
-	unsigned HOST_WIDE_INT string_length;
-	const char *p1 = c_getstr (arg0, &string_length);
-	if (p1)
-	  {
-	    const char *r
-	      = (const char *)memchr (p1, c, MIN (length, string_length));
-	    if (r == NULL && length <= string_length)
-	      return build_int_cst (type, 0);
-	  }
-
-	break;
-      }
-    default:
-      break;
-    }
-
   return NULL_TREE;
 }
 
@@ -1531,47 +1501,69 @@  tree
 fold_const_call (combined_fn fn, tree type, tree arg0, tree arg1, tree arg2)
 {
   const char *p0, *p1;
+  char c;
   unsigned HOST_WIDE_INT s0, s1;
   size_t s2 = 0;
   switch (fn)
     {
     case CFN_BUILT_IN_STRNCMP:
-      {
-	bool const_size_p = host_size_t_cst_p (arg2, &s2);
-	if (const_size_p && s2 == 0
-	    && !TREE_SIDE_EFFECTS (arg0)
-	    && !TREE_SIDE_EFFECTS (arg1))
-	  return build_int_cst (type, 0);
-	else if (const_size_p
-		 && (p0 = c_getstr (arg0))
-		 && (p1 = c_getstr (arg1)))
-	  return build_int_cst (type, strncmp (p0, p1, s2));
+      if (!host_size_t_cst_p (arg2, &s2))
 	return NULL_TREE;
-      }
+      if (s2 == 0
+	  && !TREE_SIDE_EFFECTS (arg0)
+	  && !TREE_SIDE_EFFECTS (arg1))
+	return build_int_cst (type, 0);
+      else if ((p0 = c_getstr (arg0)) && (p1 = c_getstr (arg1)))
+	return build_int_cst (type, strncmp (p0, p1, s2));
+      return NULL_TREE;
+
     case CFN_BUILT_IN_STRNCASECMP:
-      {
-	bool const_size_p = host_size_t_cst_p (arg2, &s2);
-	if (const_size_p && s2 == 0
-	    && !TREE_SIDE_EFFECTS (arg0)
-	    && !TREE_SIDE_EFFECTS (arg1))
-	  return build_int_cst (type, 0);
-	else if (const_size_p
-		 && (p0 = c_getstr (arg0))
-		 && (p1 = c_getstr (arg1))
-		 && strncmp (p0, p1, s2) == 0)
-	  return build_int_cst (type, 0);
+      if (!host_size_t_cst_p (arg2, &s2))
 	return NULL_TREE;
-      }
+      if (s2 == 0
+	  && !TREE_SIDE_EFFECTS (arg0)
+	  && !TREE_SIDE_EFFECTS (arg1))
+	return build_int_cst (type, 0);
+      else if ((p0 = c_getstr (arg0))
+	       && (p1 = c_getstr (arg1))
+	       && strncmp (p0, p1, s2) == 0)
+	return build_int_cst (type, 0);
+      return NULL_TREE;
+
     case CFN_BUILT_IN_BCMP:
     case CFN_BUILT_IN_MEMCMP:
+      if (!host_size_t_cst_p (arg2, &s2))
+	return NULL_TREE;
+      if (s2 == 0
+	  && !TREE_SIDE_EFFECTS (arg0)
+	  && !TREE_SIDE_EFFECTS (arg1))
+	return build_int_cst (type, 0);
       if ((p0 = c_getstr (arg0, &s0))
 	  && (p1 = c_getstr (arg1, &s1))
-	  && host_size_t_cst_p (arg2, &s2)
 	  && s2 <= s0
 	  && s2 <= s1)
 	return build_cmp_result (type, memcmp (p0, p1, s2));
       return NULL_TREE;
 
+    case CFN_BUILT_IN_MEMCHR:
+      if (!host_size_t_cst_p (arg2, &s2))
+	return NULL_TREE;
+      if (s2 == 0
+	  && !TREE_SIDE_EFFECTS (arg0)
+	  && !TREE_SIDE_EFFECTS (arg1))
+	return build_int_cst (type, 0);
+      if ((p0 = c_getstr (arg0, &s0))
+	  && s2 <= s0
+	  && target_char_cst_p (arg1, &c))
+	{
+	  const char *r = (const char *) memchr (p0, c, s2);
+	  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, arg2);
     }
--- gcc/testsuite/g++.dg/cpp0x/constexpr-memchr.C.jj	2016-12-05 14:27:44.234766393 +0100
+++ gcc/testsuite/g++.dg/cpp0x/constexpr-memchr.C	2016-12-05 14:26:44.000000000 +0100
@@ -0,0 +1,24 @@ 
+// { dg-do compile { target c++11 } }
+
+typedef decltype (sizeof (0)) size_t;
+constexpr const void *f1 (const char *p, int q) { return __builtin_memchr (p, q, __builtin_strlen (p) + 1); }
+constexpr const void *f2 (const char *p, int q, size_t r) { return __builtin_memchr (p, q, r); }
+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', 6) == nullptr, "");
+static_assert (f2 ("abcde", 'f', 1) == nullptr, "");
+static_assert (f2 ("abcde", 'f', 0) == nullptr, "");
+static_assert (f2 (a, 'g', 7) == nullptr, "");
+static_assert (f2 (a, 'g', 0) == nullptr, "");
+static_assert (f2 (a, 'f', 6) == a + 5, "");
+static_assert (f2 (a, 'f', 5) == nullptr, "");
+static_assert (f2 (a, 'c', 12) == a + 2, "");
+static_assert (f2 (a, 'c', 3) == a + 2, "");
+static_assert (f2 (a, 'c', 2) == nullptr, "");
+static_assert (f2 (a, '\0', 12) == a + 11, "");
+static_assert (f2 (a, '\0', 11) == nullptr, "");
+static_assert (f2 (a, '\0', 0) == nullptr, "");