Re: [PATCH] Fold __builtin_memchr (simplified version 4)

[Richard Biener]

On Thu, Oct 13, 2016 at 5:26 PM, Martin Liška  wrote:
> Simplified version that supports only valid null-terminated string constants.
> Apart from that, I added checking for constant folding of expressions that
> have side effects.
>
> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
>
> Ready to be installed?

Ok.

Richard.

> Martin

[PATCH] Fold __builtin_memchr (simplified version 4)

[Martin Liška]

Simplified version that supports only valid null-terminated string constants.
Apart from that, I added checking for constant folding of expressions that
have side effects.

Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.

Ready to be installed?
Martin
>From 5028bf5cf23cda31e72a342b821474ed0c3c07b9 Mon Sep 17 00:00:00 2001
From: marxin 
Date: Thu, 13 Oct 2016 10:30:56 +0200
Subject: [PATCH 3/4] Fold __builtin_memchr function

gcc/ChangeLog:

2016-10-13  Martin Liska  

	* builtins.h(target_char_cst_p): Declare the function.
	* builtins.c (fold_builtin_memchr): Remove.
	(target_char_cst_p): Move the function from gimple-fold.c.
	(fold_builtin_3): Do not call the function.
	* gimple-fold.c (gimple_fold_builtin_memchr): New function.
	(gimple_fold_builtin): Call the function.
	* fold-const-call.c (fold_const_call_1): Handle CFN_BUILT_IN_MEMCHR.
---
 gcc/builtins.c| 59 ++-
 gcc/builtins.h|  1 +
 gcc/fold-const-call.c | 31 +
 gcc/gimple-fold.c | 77 +--
 4 files changed, 109 insertions(+), 59 deletions(-)

diff --git a/gcc/builtins.c b/gcc/builtins.c
index ed5a635..03d8563 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -148,7 +148,6 @@ static tree rewrite_call_expr (location_t, tree, int, tree, int, ...);
 static bool validate_arg (const_tree, enum tree_code code);
 static rtx expand_builtin_fabs (tree, rtx, rtx);
 static rtx expand_builtin_signbit (tree, rtx);
-static tree fold_builtin_memchr (location_t, tree, tree, tree, tree);
 static tree fold_builtin_memcmp (location_t, tree, tree, tree);
 static tree fold_builtin_isascii (location_t, tree);
 static tree fold_builtin_toascii (location_t, tree);
@@ -7242,47 +7241,6 @@ fold_builtin_sincos (location_t loc,
 			 fold_build1_loc (loc, REALPART_EXPR, type, call)));
 }
 
-/* Fold function call to builtin memchr.  ARG1, ARG2 and LEN are the
-   arguments to the call, and TYPE is its return type.
-   Return NULL_TREE if no simplification can be made.  */
-
-static tree
-fold_builtin_memchr (location_t loc, tree arg1, tree arg2, tree len, tree type)
-{
-  if (!validate_arg (arg1, POINTER_TYPE)
-  || !validate_arg (arg2, INTEGER_TYPE)
-  || !validate_arg (len, INTEGER_TYPE))
-return NULL_TREE;
-  else
-{
-  const char *p1;
-
-  if (TREE_CODE (arg2) != INTEGER_CST
-	  || !tree_fits_uhwi_p (len))
-	return NULL_TREE;
-
-  p1 = c_getstr (arg1);
-  if (p1 && compare_tree_int (len, strlen (p1) + 1) <= 0)
-	{
-	  char c;
-	  const char *r;
-	  tree tem;
-
-	  if (target_char_cast (arg2, ))
-	return NULL_TREE;
-
-	  r = (const char *) memchr (p1, c, tree_to_uhwi (len));
-
-	  if (r == NULL)
-	return build_int_cst (TREE_TYPE (arg1), 0);
-
-	  tem = fold_build_pointer_plus_hwi_loc (loc, arg1, r - p1);
-	  return fold_convert_loc (loc, type, tem);
-	}
-  return NULL_TREE;
-}
-}
-
 /* Fold function call to builtin memcmp with arguments ARG1 and ARG2.
Return NULL_TREE if no simplification can be made.  */
 
@@ -8338,9 +8296,6 @@ fold_builtin_3 (location_t loc, tree fndecl,
 	return do_mpfr_remquo (arg0, arg1, arg2);
 break;
 
-case BUILT_IN_MEMCHR:
-  return fold_builtin_memchr (loc, arg0, arg1, arg2, type);
-
 case BUILT_IN_BCMP:
 case BUILT_IN_MEMCMP:
   return fold_builtin_memcmp (loc, arg0, arg1, arg2);;
@@ -9906,3 +9861,17 @@ is_inexpensive_builtin (tree decl)
 
   return false;
 }
+
+/* Return true if T is a constant and the value cast to a target char
+   can be represented by a host char.
+   Store the casted char constant in *P if so.  */
+
+bool
+target_char_cst_p (tree t, char *p)
+{
+  if (!tree_fits_uhwi_p (t) || CHAR_TYPE_SIZE != HOST_BITS_PER_CHAR)
+return false;
+
+  *p = (char)tree_to_uhwi (t);
+  return true;
+}
diff --git a/gcc/builtins.h b/gcc/builtins.h
index 8d0acd0..5e83646 100644
--- a/gcc/builtins.h
+++ b/gcc/builtins.h
@@ -97,6 +97,7 @@ extern unsigned HOST_WIDE_INT target_percent;
 extern char target_percent_s[3];
 extern char target_percent_c[3];
 extern char target_percent_s_newline[4];
+extern bool target_char_cst_p (tree t, char *p);
 
 extern internal_fn associated_internal_fn (tree);
 extern internal_fn replacement_internal_fn (gcall *);
diff --git a/gcc/fold-const-call.c b/gcc/fold-const-call.c
index f67b245..05a15f9 100644
--- a/gcc/fold-const-call.c
+++ b/gcc/fold-const-call.c
@@ -28,6 +28,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "fold-const-call.h"
 #include "case-cfn-macros.h"
 #include "tm.h" /* For C[LT]Z_DEFINED_AT_ZERO.  */
+#include "builtins.h"
 
 /* Functions that test for certain constant types, abstracting away the
decision about whether to check for overflow.  */
@@ -1463,6 +1464,36 @@ fold_const_call_1 (combined_fn fn, tree type, tree arg0, tree arg1, tree arg2)
   return NULL_TREE;
 }
 
+  switch (fn)
+{
+case