+/*
+ * Copyright (C) 1995-2007 University of Karlsruhe. All right reserved.
+ *
+ * This file is part of libFirm.
+ *
+ * This file may be distributed and/or modified under the terms of the
+ * GNU General Public License version 2 as published by the Free Software
+ * Foundation and appearing in the file LICENSE.GPL included in the
+ * packaging of this file.
+ *
+ * Licensees holding valid libFirm Professional Edition licenses may use
+ * this file in accordance with the libFirm Commercial License.
+ * Agreement provided with the Software.
+ *
+ * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
+ * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE.
+ */
+
/**
- * Project: libFIRM
- * File name: ir/opt/opt_osr.h
- * Purpose: Operator Strength Reduction,
- * Keith D. Cooper, L. Taylor Simpson, Christopher A. Vick
- * Author: Michael Beck
- * Modified by:
- * Created: 12.5.2006
- * CVS-ID: $Id$
- * Copyright: (c) 2006 Universität Karlsruhe
- * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
+ * @file
+ * @brief Operator Strength Reduction.
+ * @date 12.5.2006
+ * @author Michael Beck
+ * @version $Id$
+ * @summary
+ * Implementation of the Operator Strength Reduction algorithm
+ * by Keith D. Cooper, L. Taylor Simpson, Christopher A. Vick.
*/
-#ifndef _OPT_OSR_H_
-#define _OPT_OSR_H_
+#ifndef FIRM_OPT_OPT_OSR_H
+#define FIRM_OPT_OPT_OSR_H
#include "firm_types.h"
-enum osr_flags {
+/** Possible flags for the Operator Scalar Replacement. */
+typedef enum osr_flags {
osr_flag_none = 0, /**< no additional flags */
- osr_flag_lftr_with_ov_check = 1, /**< do only linear function test replacement
- if no overflow occurs. */
- /** default setting */
- osr_flag_default = osr_flag_lftr_with_ov_check
+ osr_flag_lftr_with_ov_check = 1, /**< do linear function test replacement
+ only if no overflow can occur. */
+ osr_flag_ignore_x86_shift = 2 /**< ignore Multiplications by 2, 4, 8 */
} osr_flags;
+/* FirmJNI cannot handle identical enum values... */
+
+/** default setting */
+#define osr_flag_default osr_flag_lftr_with_ov_check
+
/**
* Do the Operator Scalar Replacement optimization and linear
* function test replacement for loop control.
+ * Can be switched off using the set_opt_strength_red() flag.
+ * In that case, only remove_phi_cycles() is executed.
*
* @param irg the graph which should be optimized
- * @param flags one of osr_flags
+ * @param flags set of osr_flags
*
* The linear function replacement test is controlled by the flags.
* If the osr_flag_lftr_with_ov_check is set, the replacement is only
* done if do overflow can occur.
- * Otherwise it is ALWAYS done which might be unsure.
+ * Otherwise it is ALWAYS done which might be insecure.
*
* For instance:
*
*
* because of overflow.
*
+ * More bad cases:
+ *
+ * for (i = 0; i <= 0xF; ++i)
+ *
+ * will NOT be transformed into
+ *
+ * for (i = 0xFFFFFFF0; i <= 0xFFFFFFFF; ++i)
+ *
+ * although here is no direct overflow. The OV occurs when the ++i
+ * is executed (and would created an endless loop here!).
+ *
+ * For the same reason, a loop
+ *
+ * for (i = 0; i <= 9; i += x)
+ *
+ * will NOT be transformed because we cannot estimate whether an overflow
+ * might happen adding x.
+ *
* Note that i < a + 400 is also not possible with the current implementation
* although this might be allowed by other compilers...
+ *
+ * Note further that tests for equality can be handled some simpler (but are not
+ * implemented yet).
+ *
+ * This algorithm destroys the link field of nodes.
*/
void opt_osr(ir_graph *irg, unsigned flags);
-#endif /* _OPT_OSR_H_ */
+/**
+ * Removes useless Phi cycles, i.e cycles of Phi nodes with only one
+ * non-Phi node.
+ * This is automatically done in opt_osr(), so there is no need to call it
+ * additionally.
+ *
+ * @param irg the graph which should be optimized
+ *
+ * This algorithm destroys the link field of nodes.
+ */
+void remove_phi_cycles(ir_graph *irg);
+
+#endif /* FIRM_OPT_OPT_OSR_H */
projects / libfirm / blobdiff