re PR tree-optimization/47179 (SPU: errno misoptimization around malloc call)

	PR tree-optimization/47179
	* config/spu/spu.c (spu_ref_may_alias_errno): New function.
	(TARGET_REF_MAY_ALIAS_ERRNO): Define.

From-SVN: r168961

gcc/ChangeLog

+2011-01-18  Ulrich Weigand  <Ulrich.Weigand@de.ibm.com>
+
+	PR tree-optimization/47179
+	* config/spu/spu.c (spu_ref_may_alias_errno): New function.
+	(TARGET_REF_MAY_ALIAS_ERRNO): Define.
+
 2011-01-18  Richard Guenther  <rguenther@suse.de>
 
 	PR rtl-optimization/47216

gcc/config/spu/spu.c

@@ -230,6 +230,7 @@ static void spu_unique_section (tree, int);
 static rtx spu_expand_load (rtx, rtx, rtx, int);
 static void spu_trampoline_init (rtx, tree, rtx);
 static void spu_conditional_register_usage (void);
+static bool spu_ref_may_alias_errno (ao_ref *);
 
 /* Which instruction set architecture to use.  */
 int spu_arch;
@@ -491,6 +492,9 @@ static const struct attribute_spec spu_attribute_table[] =
 #undef TARGET_CONDITIONAL_REGISTER_USAGE
 #define TARGET_CONDITIONAL_REGISTER_USAGE spu_conditional_register_usage
 
+#undef TARGET_REF_MAY_ALIAS_ERRNO
+#define TARGET_REF_MAY_ALIAS_ERRNO spu_ref_may_alias_errno
+
 struct gcc_target targetm = TARGET_INITIALIZER;
 
 static void
@@ -7150,4 +7154,28 @@ spu_function_profiler (FILE * file, int labelno ATTRIBUTE_UNUSED)
   fprintf (file, "brsl $75,  _mcount\n");
 }
 
+/* Implement targetm.ref_may_alias_errno.  */
+static bool
+spu_ref_may_alias_errno (ao_ref *ref)
+{
+  tree base = ao_ref_base (ref);
+
+  /* With SPU newlib, errno is defined as something like
+         _impure_data._errno
+     The default implementation of this target macro does not
+     recognize such expressions, so special-code for it here.  */
+
+  if (TREE_CODE (base) == VAR_DECL
+      && !TREE_STATIC (base)
+      && DECL_EXTERNAL (base)
+      && TREE_CODE (TREE_TYPE (base)) == RECORD_TYPE
+      && strcmp (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (base)),
+		 "_impure_data") == 0
+      /* _errno is the first member of _impure_data.  */
+      && ref->offset == 0)
+    return true;
+
+  return default_ref_may_alias_errno (ref);
+}
+
 #include "gt-spu.h"