diff mbox

Fix PR79547

Message ID alpine.LSU.2.20.1702161325270.6076@zhemvz.fhfr.qr
State New
Headers show

Commit Message

Richard Biener Feb. 16, 2017, 12:26 p.m. UTC 
I am testing the following patch for PR79547.  Those builtins do not
return anything that can be used to re-construct the pointer(s) passed
to them.

Queued for GCC 8.

Richard.

2017-02-16  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/79547
	* tree-ssa-structalias.c (find_func_aliases_for_builtin_call):
	Handle strlen, strcmp, strncmp, strcasecmp, strncasecmp, memcmp,
	bcmp, strspn, strcspn, __builtin_object_size and __builtin_constant_p
	without any constraints.

	* gcc.dg/tree-ssa/strlen-2.c: New testcase.
diff mbox

Patch

Index: gcc/tree-ssa-structalias.c
===================================================================
--- gcc/tree-ssa-structalias.c	(revision 245501)
+++ gcc/tree-ssa-structalias.c	(working copy)
@@ -4474,6 +4474,22 @@  find_func_aliases_for_builtin_call (stru
 	    process_all_all_constraints (lhsc, rhsc);
 	  }
 	return true;
+      /* Pure functions that return something not based on any object.  */
+      case BUILT_IN_STRLEN:
+      case BUILT_IN_STRCMP:
+      case BUILT_IN_STRNCMP:
+      case BUILT_IN_STRCASECMP:
+      case BUILT_IN_STRNCASECMP:
+      case BUILT_IN_MEMCMP:
+      case BUILT_IN_BCMP:
+      case BUILT_IN_STRSPN:
+      case BUILT_IN_STRCSPN:
+      case BUILT_IN_OBJECT_SIZE:
+      case BUILT_IN_CONSTANT_P:
+	/* We don't need to do anything here.  No constraints are necessary
+	   for the return value and call handling for pure functions is
+	   special-cased in the alias oracle.  */
+	return true;
       /* Trampolines are special - they set up passing the static
 	 frame.  */
       case BUILT_IN_INIT_TRAMPOLINE:
Index: gcc/testsuite/gcc.dg/tree-ssa/strlen-2.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/strlen-2.c	(nonexistent)
+++ gcc/testsuite/gcc.dg/tree-ssa/strlen-2.c	(working copy)
@@ -0,0 +1,15 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+void f (unsigned);
+
+void f3 (void)
+{
+  char s[] = "1234";
+
+  f (__builtin_strlen (s));
+  f (__builtin_strlen (s));
+  f (__builtin_strlen (s));
+}
+
+/* { dg-final { scan-tree-dump-times "strlen" 1 "strlen" } } */