Re: Move some bit and binary optimizations in simplify and match

["Hurugalawadi, Naveen" <Naveen.Hurugalawadi@caviumnetworks.com>]

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Hi,

Thanks for all the suggestions.
Please find attached the modified patch as per your suggestions.

I had missed a mail as pointed by Marc Glisse. Now I have implemented
everything suggested.
Please review the patch and let me know if any further modifications are required.

I have some queries regarding the whole discussions along the course of
this patch.
It would be very helpful for my understanding of the code.

>> /* Fold (A & ~B) - (A & B) into (A ^ B) - B.  */
>> Likewise the fold code handles both constant and non-constant B.

How do we know that fold code handles both constant and non-constant B
and not A?

>> Fold (a * (1 << b)) into (a << b)
>> So either way I think we should only allow nop conversions
>> here (as fold-const.c did).

How do we recognize from the fold-const code that it allows only nop
conversions.

>> We want to minimize the number of lines in match.pd and this doesn't
>> really achieve this compared to duplicating the whole pattern.

Yes. Even, I have the same question to understand this better.
Is it worth and does it acheive any extra optimization after moving
it using simplify and match?

Should I have the other three patterns duplicated and implemented
or leave it in fold-const code?

Thanks,
Naveen

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diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index de45a2c..1e7fbb4 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -9803,20 +9803,6 @@ fold_binary_loc (location_t loc,
       goto associate;
 
     case MULT_EXPR:
-      /* (-A) * (-B) -> A * B  */
-      if (TREE_CODE (arg0) == NEGATE_EXPR && negate_expr_p (arg1))
-	return fold_build2_loc (loc, MULT_EXPR, type,
-			    fold_convert_loc (loc, type,
-					      TREE_OPERAND (arg0, 0)),
-			    fold_convert_loc (loc, type,
-					      negate_expr (arg1)));
-      if (TREE_CODE (arg1) == NEGATE_EXPR && negate_expr_p (arg0))
-	return fold_build2_loc (loc, MULT_EXPR, type,
-			    fold_convert_loc (loc, type,
-					      negate_expr (arg0)),
-			    fold_convert_loc (loc, type,
-					      TREE_OPERAND (arg1, 0)));
-
       if (! FLOAT_TYPE_P (type))
 	{
 	  /* Transform x * -C into -x * C if x is easily negatable.  */
@@ -9830,16 +9816,6 @@ fold_binary_loc (location_t loc,
 						  negate_expr (arg0)),
 				tem);
 
-	  /* (a * (1 << b)) is (a << b)  */
-	  if (TREE_CODE (arg1) == LSHIFT_EXPR
-	      && integer_onep (TREE_OPERAND (arg1, 0)))
-	    return fold_build2_loc (loc, LSHIFT_EXPR, type, op0,
-				TREE_OPERAND (arg1, 1));
-	  if (TREE_CODE (arg0) == LSHIFT_EXPR
-	      && integer_onep (TREE_OPERAND (arg0, 0)))
-	    return fold_build2_loc (loc, LSHIFT_EXPR, type, op1,
-				TREE_OPERAND (arg0, 1));
-
 	  /* (A + A) * C -> A * 2 * C  */
 	  if (TREE_CODE (arg0) == PLUS_EXPR
 	      && TREE_CODE (arg1) == INTEGER_CST
@@ -9882,21 +9858,6 @@ fold_binary_loc (location_t loc,
 	}
       else
 	{
-	  /* Convert (C1/X)*C2 into (C1*C2)/X.  This transformation may change
-             the result for floating point types due to rounding so it is applied
-             only if -fassociative-math was specify.  */
-	  if (flag_associative_math
-	      && TREE_CODE (arg0) == RDIV_EXPR
-	      && TREE_CODE (arg1) == REAL_CST
-	      && TREE_CODE (TREE_OPERAND (arg0, 0)) == REAL_CST)
-	    {
-	      tree tem = const_binop (MULT_EXPR, TREE_OPERAND (arg0, 0),
-				      arg1);
-	      if (tem)
-		return fold_build2_loc (loc, RDIV_EXPR, type, tem,
-				    TREE_OPERAND (arg0, 1));
-	    }
-
           /* Strip sign operations from X in X*X, i.e. -Y*-Y -> Y*Y.  */
 	  if (operand_equal_p (arg0, arg1, 0))
 	    {
@@ -10053,22 +10014,6 @@ fold_binary_loc (location_t loc,
       goto bit_rotate;
 
     case BIT_AND_EXPR:
-      /* ~X & X, (X == 0) & X, and !X & X are always zero.  */
-      if ((TREE_CODE (arg0) == BIT_NOT_EXPR
-	   || TREE_CODE (arg0) == TRUTH_NOT_EXPR
-	   || (TREE_CODE (arg0) == EQ_EXPR
-	       && integer_zerop (TREE_OPERAND (arg0, 1))))
-	  && operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0))
-	return omit_one_operand_loc (loc, type, integer_zero_node, arg1);
-
-      /* X & ~X , X & (X == 0), and X & !X are always zero.  */
-      if ((TREE_CODE (arg1) == BIT_NOT_EXPR
-	   || TREE_CODE (arg1) == TRUTH_NOT_EXPR
-	   || (TREE_CODE (arg1) == EQ_EXPR
-	       && integer_zerop (TREE_OPERAND (arg1, 1))))
-	  && operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0))
-	return omit_one_operand_loc (loc, type, integer_zero_node, arg0);
-
       /* Fold (X ^ 1) & 1 as (X & 1) == 0.  */
       if (TREE_CODE (arg0) == BIT_XOR_EXPR
 	  && INTEGRAL_TYPE_P (type)
diff --git a/gcc/match.pd b/gcc/match.pd
index 655c9ff..2e0b919 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -323,6 +323,27 @@ along with GCC; see the file COPYING3.  If not see
     (if (real_isinteger (&TREE_REAL_CST (@1), &n) && (n & 1) == 0)
      (pows @0 @1))))))
 
+/* Fold (a * (1 << b)) into (a << b)  */
+(simplify
+ (mult:c @0 (lshift integer_onep@1 @2))
+  (if (! FLOAT_TYPE_P (type)
+       && tree_nop_conversion_p (type, TREE_TYPE (@1)))
+   (lshift @0 @2)))
+
+/* Fold (C1/X)*C2 into (C1*C2)/X.  */
+(simplify
+ (mult (rdiv:s REAL_CST@0 @1) REAL_CST@2)
+  (if (flag_associative_math)
+  (with
+   { tree tem = const_binop (MULT_EXPR, type, @0, @2); }
+  (if (tem)
+   (rdiv { tem; } @1)))))
+
+/* Simplify ~X & X as zero.  */
+(simplify
+ (bit_and:c (convert? @0) (convert? (bit_not @0)))
+  { build_zero_cst (type); })
+
 /* X % Y is smaller than Y.  */
 (for cmp (lt ge)
  (simplify
@@ -542,6 +563,13 @@ along with GCC; see the file COPYING3.  If not see
 (match negate_expr_p
  VECTOR_CST
  (if (FLOAT_TYPE_P (TREE_TYPE (type)) || TYPE_OVERFLOW_WRAPS (type))))
+
+/* (-A) * (-B) -> A * B  */
+(simplify
+ (mult:c (convert1? (negate @0)) (convert2? negate_expr_p@1))
+  (if (tree_nop_conversion_p (type, TREE_TYPE (@0))
+       && tree_nop_conversion_p (type, TREE_TYPE (@1)))
+   (mult (convert @0) (convert (negate @1)))))
  
 /* -(A + B) -> (-B) - A.  */
 (simplify