Introduce flip-flopping normalisations

There are cases where we can normalize in 2 directions and both have
their merits. Just do both in this case. The frontend should at some
point set IRG_GRAPH_STATE_NORMALISATION2 to trigger the 2nd direction.

include/libfirm/irgraph.h

@@ -514,6 +514,12 @@ typedef enum {
 	IR_GRAPH_STATE_ARCH_DEP      = 1U << 1,  /**< should not construct more nodes which irarch potentially breaks down */
 	IR_GRAPH_STATE_BCONV_ALLOWED = 1U << 2,  /**< Conv(mode_b) to Iu is allowed as set command */
 	IR_GRAPH_STATE_BAD_BLOCK     = 1U << 3,  /**< a node may have Bad in its block input */
+	/**
+	 * There are normalisations where there is no "best" representative.
+	 * In this case we first normalise into 1 direction (!NORMALISATION2) and
+	 * later in the other (NORMALISATION2).
+	 */
+	IR_GRAPH_STATE_NORMALISATION2        = 1U << 4,
 } ir_graph_state_t;
 ENUM_BITSET(ir_graph_state_t)
 

ir/ir/iropt.c

@@ -2181,6 +2181,7 @@ restart:
 		}
 		DBG_OPT_ALGSIM0(oldn, n, FS_OPT_SUB_TO_ADD);
 		return n;
+#if 0
 	} else if (is_Mul(b)) { /* a - (b * C) -> a + (b * -C) */
 		ir_node *m_right = get_Mul_right(b);
 		if (is_Const(m_right)) {
@@ -2199,6 +2200,7 @@ restart:
 				return n;
 			}
 		}
+#endif
 	}
 
 	/* Beware of Sub(P, P) which cannot be optimized into a simple Minus ... */
@@ -2930,15 +2932,109 @@ static bool is_shiftop(const ir_node *n)
 	return is_Shl(n) || is_Shr(n) || is_Shrs(n) || is_Rotl(n);
 }
 
+/**
+ * normalisation: (x & c1) >> c2   to   (x >> c2) & (c1 >> c2)
+ *  (we can use:
+ *    - and, or, xor          instead of &
+ *    - Shl, Shr, Shrs, rotl  instead of >>
+ *    (with a special case for Or/Xor + Shrs)
+ *
+ * This normalisation is good for things like x-(x&y) esp. in 186.crafty.
+ */
+static ir_node *transform_node_shift_bitop(ir_node *n)
+{
+	ir_graph  *irg   = get_irn_irg(n);
+	ir_node   *right = get_binop_right(n);
+	ir_mode   *mode  = get_irn_mode(n);
+	ir_node   *left;
+	ir_node   *bitop_left;
+	ir_node   *bitop_right;
+	ir_op     *op_left;
+	ir_node   *block;
+	dbg_info  *dbgi;
+	ir_node   *new_shift;
+	ir_node   *new_bitop;
+	ir_node   *new_const;
+	ir_tarval *tv1;
+	ir_tarval *tv2;
+	ir_tarval *tv_shift;
+
+	if (is_irg_state(irg, IR_GRAPH_STATE_NORMALISATION2))
+		return n;
+
+	assert(is_Shrs(n) || is_Shr(n) || is_Shl(n) || is_Rotl(n));
+
+	if (!is_Const(right))
+		return n;
+
+	left    = get_binop_left(n);
+	op_left = get_irn_op(left);
+	if (op_left != op_And && op_left != op_Or && op_left != op_Eor)
+		return n;
+
+	/* doing it with Shrs is not legal if the Or/Eor affects the topmost bit */
+	if (is_Shrs(n) && (op_left == op_Or || op_left == op_Eor)) {
+		/* TODO: test if sign bit is affectes */
+		return n;
+	}
+
+	bitop_right = get_binop_right(left);
+	if (!is_Const(bitop_right))
+		return n;
+
+	bitop_left = get_binop_left(left);
+
+	block = get_nodes_block(n);
+	dbgi  = get_irn_dbg_info(n);
+	tv1   = get_Const_tarval(bitop_right);
+	tv2   = get_Const_tarval(right);
+
+	assert(get_tarval_mode(tv1) == mode);
+
+	if (is_Shl(n)) {
+		new_shift = new_rd_Shl(dbgi, block, bitop_left, right, mode);
+		tv_shift  = tarval_shl(tv1, tv2);
+	} else if (is_Shr(n)) {
+		new_shift = new_rd_Shr(dbgi, block, bitop_left, right, mode);
+		tv_shift  = tarval_shr(tv1, tv2);
+	} else if (is_Shrs(n)) {
+		new_shift = new_rd_Shrs(dbgi, block, bitop_left, right, mode);
+		tv_shift  = tarval_shrs(tv1, tv2);
+	} else {
+		assert(is_Rotl(n));
+		new_shift = new_rd_Rotl(dbgi, block, bitop_left, right, mode);
+		tv_shift  = tarval_rotl(tv1, tv2);
+	}
+
+	assert(get_tarval_mode(tv_shift) == mode);
+	irg       = get_irn_irg(n);
+	new_const = new_r_Const(irg, tv_shift);
+
+	if (op_left == op_And) {
+		new_bitop = new_rd_And(dbgi, block, new_shift, new_const, mode);
+	} else if (op_left == op_Or) {
+		new_bitop = new_rd_Or(dbgi, block, new_shift, new_const, mode);
+	} else {
+		assert(op_left == op_Eor);
+		new_bitop = new_rd_Eor(dbgi, block, new_shift, new_const, mode);
+	}
+
+	return new_bitop;
+}
+
 /**
  * normalisation: (x >> c1) & c2   to   (x & (c2<<c1)) >> c1
  *  (we can use:
  *    - and, or, xor          instead of &
  *    - Shl, Shr, Shrs, rotl  instead of >>
  *    (with a special case for Or/Xor + Shrs)
+ *
+ * This normalisation is usually good for the backend since << C can often be
+ * matched as address-mode.
  */
 static ir_node *transform_node_bitop_shift(ir_node *n)
 {
+	ir_graph  *irg   = get_irn_irg(n);
 	ir_node   *left  = get_binop_left(n);
 	ir_node   *right = get_binop_right(n);
 	ir_mode   *mode  = get_irn_mode(n);
@@ -2947,7 +3043,6 @@ static ir_node *transform_node_bitop_shift(ir_node *n)
 	ir_node   *block;
 	dbg_info  *dbg_bitop;
 	dbg_info  *dbg_shift;
-	ir_graph  *irg;
 	ir_node   *new_bitop;
 	ir_node   *new_shift;
 	ir_node   *new_const;
@@ -2955,6 +3050,9 @@ static ir_node *transform_node_bitop_shift(ir_node *n)
 	ir_tarval *tv2;
 	ir_tarval *tv_bitop;
 
+	if (!is_irg_state(irg, IR_GRAPH_STATE_NORMALISATION2))
+		return n;
+
 	assert(is_And(n) || is_Or(n) || is_Eor(n));
 	if (!is_Const(right) || !is_shiftop(left))
 		return n;
@@ -5135,6 +5233,8 @@ static ir_node *transform_node_Shr(ir_node *n)
 		n = transform_node_shift_modulo(n, new_rd_Shr);
 	if (is_Shr(n))
 		n = transform_node_shl_shr(n);
+	if (is_Shr(n))
+		n = transform_node_shift_bitop(n);
 
 	return n;
 }  /* transform_node_Shr */
@@ -5164,6 +5264,8 @@ static ir_node *transform_node_Shrs(ir_node *n)
 
 	if (is_Shrs(n))
 		n = transform_node_shift_modulo(n, new_rd_Shrs);
+	if (is_Shrs(n))
+		n = transform_node_shift_bitop(n);
 
 	return n;
 }  /* transform_node_Shrs */
@@ -5185,6 +5287,8 @@ static ir_node *transform_node_Shl(ir_node *n)
 		n = transform_node_shift_modulo(n, new_rd_Shl);
 	if (is_Shl(n))
 		n = transform_node_shl_shr(n);
+	if (is_Shl(n))
+		n = transform_node_shift_bitop(n);
 
 	return n;
 }  /* transform_node_Shl */
@@ -5202,6 +5306,9 @@ static ir_node *transform_node_Rotl(ir_node *n)
 	HANDLE_BINOP_PHI((eval_func) tarval_rotl, a, b, c, mode);
 	n = transform_node_shift(n);
 
+	if (is_Rotl(n))
+		n = transform_node_shift_bitop(n);
+
 	return n;
 }  /* transform_node_Rotl */