[PATCH] Fix parts of PR48149

[Richard Guenther]

This fixes the easiest case in PR48149 by extending fold to handle
 COMPLEX_EXPR <REALPART_EXPR <x>, IMAGPART_EXPR <x>>.  We have to
be careful when the types do not match as fold-convert happily
re-constructs a COMPLEX_EXPR of this kind when folding a complex-expr
to a slightly different type.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

2011-03-16  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/48149
	* fold-const.c (fold_binary_loc): Fold
	COMPLEX_EXPR <REALPART_EXPR <x>, IMAGPART_EXPR <x>>.

	* gcc.dg/fold-complex-1.c: New testcase.

Index: gcc/fold-const.c
===================================================================
*** gcc/fold-const.c	(revision 171047)
--- gcc/fold-const.c	(working copy)
*************** fold_binary_loc (location_t loc,
*** 13176,13181 ****
--- 13176,13189 ----
  	  || (TREE_CODE (arg0) == INTEGER_CST
  	      && TREE_CODE (arg1) == INTEGER_CST))
  	return build_complex (type, arg0, arg1);
+       if (TREE_CODE (arg0) == REALPART_EXPR
+ 	  && TREE_CODE (arg1) == IMAGPART_EXPR
+ 	  && (TYPE_MAIN_VARIANT (TREE_TYPE (TREE_OPERAND (arg0, 0)))
+ 	      == TYPE_MAIN_VARIANT (type))
+ 	  && operand_equal_p (TREE_OPERAND (arg0, 0),
+ 			      TREE_OPERAND (arg1, 0), 0))
+ 	return omit_one_operand_loc (loc, type, TREE_OPERAND (arg0, 0),
+ 				     TREE_OPERAND (arg1, 0));
        return NULL_TREE;
  
      case ASSERT_EXPR:
Index: gcc/testsuite/gcc.dg/fold-complex-1.c
===================================================================
*** gcc/testsuite/gcc.dg/fold-complex-1.c	(revision 0)
--- gcc/testsuite/gcc.dg/fold-complex-1.c	(revision 0)
***************
*** 0 ****
--- 1,11 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -ffast-math -fdump-tree-original" } */
+ 
+ _Complex float
+ foo (_Complex float x)
+ {
+   return  __real x + 1.0iF * __imag x;
+ }
+ 
+ /* { dg-final { scan-tree-dump-times "COMPLEX_EXPR" 0 "original" } } */
+ /* { dg-final { cleanup-tree-dump "original" } } */