mirror of https://github.com/cc65/cc65.git
130 lines
4.3 KiB
C
130 lines
4.3 KiB
C
/*****************************************************************************/
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/* */
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/* coptshift.h */
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/* */
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/* Optimize shifts */
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/* */
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/* */
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/* */
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/* (C) 2001-2012, Ullrich von Bassewitz */
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/* Roemerstrasse 52 */
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/* D-70794 Filderstadt */
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/* EMail: uz@cc65.org */
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/* */
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/* */
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/* This software is provided 'as-is', without any expressed or implied */
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/* warranty. In no event will the authors be held liable for any damages */
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/* arising from the use of this software. */
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/* */
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/* Permission is granted to anyone to use this software for any purpose, */
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/* including commercial applications, and to alter it and redistribute it */
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/* freely, subject to the following restrictions: */
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/* */
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/* 1. The origin of this software must not be misrepresented; you must not */
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/* claim that you wrote the original software. If you use this software */
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/* in a product, an acknowledgment in the product documentation would be */
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/* appreciated but is not required. */
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/* 2. Altered source versions must be plainly marked as such, and must not */
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/* be misrepresented as being the original software. */
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/* 3. This notice may not be removed or altered from any source */
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/* distribution. */
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/* */
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/*****************************************************************************/
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#ifndef COPTSHIFT_H
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#define COPTSHIFT_H
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/* cc65 */
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#include "codeseg.h"
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/*****************************************************************************/
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/* Optimize shifts */
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/*****************************************************************************/
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unsigned OptShift1 (CodeSeg* S);
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/* A call to the shlaxN routine may get replaced by one or more asl insns
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** if the value of X is not used later. If X is used later, but it is zero
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** on entry and it's a shift by one, it may get replaced by:
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**
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** asl a
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** bcc L1
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** inx
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** L1:
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*/
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unsigned OptShift2 (CodeSeg* S);
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/* The sequence
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**
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** bpl L
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** dex
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** L: jsr asraxN
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**
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** might be replaced by N copies of
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**
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** cmp #$80
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** ror a
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**
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** if X is not used later (X is assumed to be zero on entry).
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*/
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unsigned OptShift3 (CodeSeg* S);
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/* The sequence
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**
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** bcc L
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** inx
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** L: jsr shrax1
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**
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** may get replaced by
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**
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** ror a
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**
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** if X is zero on entry and unused later. For shift counts > 1, more
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**
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** shr a
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**
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** must be added.
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*/
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unsigned OptShift4 (CodeSeg* S);
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/* Calls to the asraxN or shraxN routines may get replaced by one or more lsr
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** insns if the value of X is zero.
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*/
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unsigned OptShift5 (CodeSeg* S);
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/* Search for the sequence
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**
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** lda xxx
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** ldx yyy
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** jsr aslax1/asrax1/shlax1/shrax1
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** sta aaa
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** stx bbb
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**
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** and replace it by
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**
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** lda xxx
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** asl a
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** sta aaa
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** lda yyy
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** rol a
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** sta bbb
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**
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** or similar, provided that a/x is not used later
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*/
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unsigned OptShift6 (CodeSeg* S);
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/* Inline the shift subroutines. */
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/* End of coptshift.h */
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#endif
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