re PR middle-end/47735 (Unnecessary adjustments to stack pointer)

	PR middle-end/47735
	* cfgexpand.c (expand_one_var): For SSA_NAMEs, if the underlying
	var satisfies use_register_for_decl, just take into account type
	alignment, rather than decl alignment.

	* gcc.target/i386/pr47735.c: New test.

From-SVN: r206493

gcc/ChangeLog

 2014-01-09  Jakub Jelinek  <jakub@redhat.com>
 
+	PR middle-end/47735
+	* cfgexpand.c (expand_one_var): For SSA_NAMEs, if the underlying
+	var satisfies use_register_for_decl, just take into account type
+	alignment, rather than decl alignment.
+
 	PR tree-optimization/59622
 	* gimple-fold.c (gimple_fold_call): Fix a typo in message.  For
 	__builtin_unreachable replace the OBJ_TYPE_REF call with a call to

gcc/cfgexpand.c

@@ -1215,8 +1215,11 @@ expand_one_var (tree var, bool toplevel, bool really_expand)
 	 we conservatively assume it will be on stack even if VAR is
 	 eventually put into register after RA pass.  For non-automatic
 	 variables, which won't be on stack, we collect alignment of
-	 type and ignore user specified alignment.  */
-      if (TREE_STATIC (var) || DECL_EXTERNAL (var))
+	 type and ignore user specified alignment.  Similarly for
+	 SSA_NAMEs for which use_register_for_decl returns true.  */
+      if (TREE_STATIC (var)
+	  || DECL_EXTERNAL (var)
+	  || (TREE_CODE (origvar) == SSA_NAME && use_register_for_decl (var)))
 	align = MINIMUM_ALIGNMENT (TREE_TYPE (var),
 				   TYPE_MODE (TREE_TYPE (var)),
 				   TYPE_ALIGN (TREE_TYPE (var)));

gcc/testsuite/ChangeLog

 2014-01-09  Jakub Jelinek  <jakub@redhat.com>
 
+	PR middle-end/47735
+	* gcc.target/i386/pr47735.c: New test.
+
 	PR tree-optimization/59622
 	* g++.dg/opt/pr59622-2.C: New test.
 	* g++.dg/opt/pr59622-3.C: New test.

gcc/testsuite/gcc.target/i386/pr47735.c

+/* PR middle-end/47735 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fomit-frame-pointer" } */
+
+unsigned
+mulh (unsigned a, unsigned b)
+{
+  unsigned long long l __attribute__ ((aligned (32)))
+    = ((unsigned long long) a * (unsigned long long) b) >> 32;
+  return l;
+}
+
+/* No need to dynamically realign the stack here.  */
+/* { dg-final { scan-assembler-not "and\[^\n\r]*%\[re\]sp" } } */
+/* Nor use a frame pointer.  */
+/* { dg-final { scan-assembler-not "%\[re\]bp" } } */