* fold-const.c (fold): For ((a * C1) / C3) or (((a * C1) + C2) / C3)

        optimizations, look inside dividend to determine if the expression
        can be simplified by using EXACT_DIV_EXPR.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@16216 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 31 insertions, 0 deletions

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 1e823fbf4c7..da18997acc3 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -4655,6 +4655,37 @@ fold (expr)
 
 	  STRIP_NOPS (xarg0);
 
+	  /* Look inside the dividend and simplify using EXACT_DIV_EXPR
+	     if possible.  */
+	  if (TREE_CODE (xarg0) == MULT_EXPR
+	      && multiple_of_p (type, TREE_OPERAND (xarg0, 0), arg1))
+	    {
+	      tree t;
+
+	      t = fold (build (MULT_EXPR, type,
+			       fold (build (EXACT_DIV_EXPR, type,
+					    TREE_OPERAND (xarg0, 0), arg1)),
+			       TREE_OPERAND (xarg0, 1)));
+	      if (have_save_expr)
+		t = save_expr (t);
+	      return t;
+
+	    }
+
+	  if (TREE_CODE (xarg0) == MULT_EXPR
+	      && multiple_of_p (type, TREE_OPERAND (xarg0, 1), arg1))
+	    {
+	      tree t;
+
+	      t = fold (build (MULT_EXPR, type,
+			       fold (build (EXACT_DIV_EXPR, type,
+					    TREE_OPERAND (xarg0, 1), arg1)),
+			       TREE_OPERAND (xarg0, 0)));
+	      if (have_save_expr)
+		t = save_expr (t);
+	      return t;
+	    }
+
 	  if (TREE_CODE (xarg0) == PLUS_EXPR
 	      && TREE_CODE (TREE_OPERAND (xarg0, 1)) == INTEGER_CST)
 	    c2 = TREE_OPERAND (xarg0, 1), xarg0 = TREE_OPERAND (xarg0, 0);