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Technical Support
On-Line Manuals
Cx51 User's Guide
Cx51 Introduction
Compiling Programs
Language Extensions
Preprocessor
Advanced Programming
Customization Files
Startup Code
Variable Initialization Code
XBANKING.A51
Basic I/O
Memory Allocation
Optimizer
Optimizer Options
General Optimizations
8051-Specific Optimizations
Global Register Coloring
Segment Naming Conventions
Data Objects
Program Objects
Parameters and Local Variables
Interfacing C to Assembler
Global Variables
Function Parameters
Passing in Memory
Passing in Registers
Function Return Values
Using the SRC Directive
Register Usage
Overlaying Segments
Small Model Example
Compact Model Example
Large Model Example
Interfacing C programs to PL/M-51
Data Storage Formats
Bit Variables
1-Byte Scalars
2-Byte Scalars
4-Byte Scalars
Generic and Far Pointers
Floating-point Numbers
Floating-point Errors
Absolute Memory Locations
Absolute Access Macros
Linker Location Controls
The _at_ Keyword
Debugging
8051 Derivatives
Error Messages
Library Reference
Appendix
8051-Specific Optimizations
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AJMP/ACALL Maximizing (Linker Optimization) (Level 0-7)
The linker rearranges code segments to maximize AJMP and ACALL instructions which are shorter than LJMP and LCALL instructions. -
Case/Switch Optimizing (Level 4)
Code involving switch and case statements is optimized using jump tables or jump strings. -
Data Overlaying (Level
2)
Data and bit segments suitable for static overlay are identified and internally marked. The linker has the capability, through global data flow analysis, of selecting segments which can then be overlaid. -
Extended Access Optimizing (Level 4)
Variables from the IDATA, XDATA, PDATA and CODE areas are directly included in operations. Intermediate registers are frequently unnecessary. -
Peephole Optimizing (Level
3)
Redundant MOV instructions are removed. This includes unnecessary loading of objects from the memory as well as load operations with constants. Complex operations are replaced by simple operations when memory space or execution time can be saved.
Note
- Linker optimizations are performed by the LX51 Linker only. The BL51 Linker does not perform any optimizations.
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