mirror of https://github.com/cc65/cc65.git
134 lines
5.6 KiB
C
134 lines
5.6 KiB
C
/*****************************************************************************/
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/* */
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/* coptjmp.h */
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/* */
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/* Low level optimizations regarding branches and jumps */
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/* */
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/* */
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/* */
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/* (C) 2001-2009, 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 COPTJMP_H
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#define COPTJMP_H
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/* cc65 */
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#include "codeseg.h"
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/*****************************************************************************/
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/* Code */
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/*****************************************************************************/
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unsigned OptBranchDist (CodeSeg* S);
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/* Change branches for the distance needed. */
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unsigned OptBranchDist2 (CodeSeg* S);
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/* If BRA points to an external symbol, change it to JMP */
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unsigned OptRTSJumps1 (CodeSeg* S);
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/* Replace jumps to RTS by RTS */
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unsigned OptRTSJumps2 (CodeSeg* S);
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/* Replace long conditional jumps to RTS */
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unsigned OptDeadJumps (CodeSeg* S);
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/* Remove dead jumps (jumps to the next instruction) */
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unsigned OptDeadCode (CodeSeg* S);
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/* Remove dead code (code that follows an unconditional jump or an rts/rti
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** and has no label)
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*/
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unsigned OptJumpCascades (CodeSeg* S);
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/* Optimize jump cascades (jumps to jumps). In such a case, the jump is
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** replaced by a jump to the final location. This will in some cases produce
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** worse code, because some jump targets are no longer reachable by short
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** branches, but this is quite rare, so there are more advantages than
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** disadvantages.
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*/
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unsigned OptRTS (CodeSeg* S);
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/* Optimize subroutine calls followed by an RTS. The subroutine call will get
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** replaced by a jump. Don't bother to delete the RTS if it does not have a
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** label, the dead code elimination should take care of it.
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*/
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unsigned OptJumpTarget1 (CodeSeg* S);
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/* If the instruction preceeding an unconditional branch is the same as the
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** instruction preceeding the jump target, the jump target may be moved
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** one entry back. This is a size optimization, since the instruction before
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** the branch gets removed.
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*/
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unsigned OptJumpTarget2 (CodeSeg* S);
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/* If a bcs jumps to a sec insn or a bcc jumps to clc, skip this insn, since
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** it's job is already done.
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*/
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unsigned OptJumpTarget3 (CodeSeg* S);
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/* Jumps to load instructions of a register, that do already have the matching
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** register contents may skip the load instruction, since it's job is already
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** done.
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*/
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unsigned OptCondBranch1 (CodeSeg* S);
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/* Performs some optimization steps:
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** - If an immediate load of a register is followed by a conditional jump that
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** is never taken because the load of the register sets the flags in such a
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** manner, remove the conditional branch.
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** - If the conditional branch is always taken because of the register load,
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** replace it by a jmp.
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*/
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unsigned OptCondBranch2 (CodeSeg* S);
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/* If a conditional branch jumps around an unconditional branch, remove the
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** conditional branch and make the jump a conditional branch with the inverse
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** condition of the first one.
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*/
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unsigned OptCondBranch3 (CodeSeg* S);
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/* If the conditional branch is always taken because it follows an inverse
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** conditional branch, replace it by a jmp.
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*/
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unsigned OptCondBranchC (CodeSeg* S);
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/* If on entry to a "rol a" instruction the accu is zero, and a beq/bne follows,
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** we can remove the rol and branch on the state of the carry.
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*/
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/* End of coptjmp.h */
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#endif
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