re PR tree-optimization/38789 (__builtin_constant_p appears to evaluate to true…

re PR tree-optimization/38789 (__builtin_constant_p appears to evaluate to true for non-constant arguments.)

	PR tree-optimization/38789
	* tree-ssa-threadedge.c
	(record_temporary_equivalences_from_stmts_at_dest): Ignore calls to
	__builtin_constant_p.

	* gcc.c-torture/compile/pr38789.c: New test.

From-SVN: r143435

gcc/ChangeLog

+2009-01-16  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/38789
+	* tree-ssa-threadedge.c
+	(record_temporary_equivalences_from_stmts_at_dest): Ignore calls to
+	__builtin_constant_p.
+
 2009-01-16  Kenneth Zadeck <zadeck@naturalbridge.com>
 
 	* dce.c (delete_unmarked_insns): Reversed the order that insns are

gcc/testsuite/ChangeLog

+2009-01-16  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/38789
+	* gcc.c-torture/compile/pr38789.c: New test.
+
 2009-01-16  Janus Weil  <janus@gcc.gnu.org>
 
 	PR fortran/38152

gcc/testsuite/gcc.c-torture/compile/pr38789.c

+/* PR tree-optimization/38789 */
+
+void
+baz (int v)
+{
+  unsigned a = (v == 1) ? 1 : 2;
+
+  if (__builtin_constant_p (a))
+    asm volatile ("# constant %0" :: "i" (a));
+  else
+    asm volatile ("# register %0" :: "r" (a));
+
+  a = 6;
+  if (__builtin_constant_p (a))
+    asm volatile ("# constant %0" :: "i" (a));
+  else
+    asm volatile ("# register %0" :: "r" (a));
+}

gcc/tree-ssa-threadedge.c

 /* SSA Jump Threading
-   Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
+   Copyright (C) 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
    Contributed by Jeff Law  <law@redhat.com>
 
 This file is part of GCC.
@@ -320,12 +320,22 @@ record_temporary_equivalences_from_stmts_at_dest (edge e,
 
 	 The result of __builtin_object_size is defined to be the maximum of
 	 remaining bytes. If we use only one edge on the phi, the result will
-	 change to be the remaining bytes for the corresponding phi argument. */
+	 change to be the remaining bytes for the corresponding phi argument.
+
+	 Similarly for __builtin_constant_p:
+
+	 r = PHI <1(2), 2(3)>
+	 __builtin_constant_p (r)
+
+	 Both PHI arguments are constant, but x ? 1 : 2 is still not
+	 constant.  */
 
       if (is_gimple_call (stmt))
 	{
 	  tree fndecl = gimple_call_fndecl (stmt);
-	  if (fndecl && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_OBJECT_SIZE)
+	  if (fndecl
+	      && (DECL_FUNCTION_CODE (fndecl) == BUILT_IN_OBJECT_SIZE
+		  || DECL_FUNCTION_CODE (fndecl) == BUILT_IN_CONSTANT_P))
 	    continue;
 	}