46 lines
1.7 KiB
Plaintext
46 lines
1.7 KiB
Plaintext
Copyright (c) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
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DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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This code is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License version 2 only, as
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published by the Free Software Foundation.
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This code is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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version 2 for more details (a copy is included in the LICENSE file that
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accompanied this code).
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You should have received a copy of the GNU General Public License version
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2 along with this work; if not, write to the Free Software Foundation,
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Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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or visit www.oracle.com if you need additional information or have any
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questions.
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Constant Propagation
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--------------------
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Constant propagation is a code reduction technique in which values of variables
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which are determined to be constants can be passed to expressions which use
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these constants and can be computed at compile time.
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Example:
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Consider the following segment of an original source program:
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x = 7;
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y = 2 * x;
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z = f (x, y);
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The value of variable x in the segment's last two lines is the constant number 7.
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This is always true, because of the assignment to x in the segment's first line.
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Therefore, the two instances of x can be substituted by the constant value 7
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(this value propagates through the next two lines). The reduced source program
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is the following:
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x = 7;
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y = 2 * 7;
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z = f (7, y);
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