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C–– Efficiency
5-37Code Development Tools
C to ASM function return
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|Return Addr | |Return Addr |
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|Return Addr | |Return Addr |
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R7 |Param 2 | |Param 2 |
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|Param 2 | |Param 2 |
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|Param 1 | |Param 1 |
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|Param 1 | |Param 1 |
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R5 |Stack data |R7,R5 |Stack data|
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RET SUBB R7, 4
5.7 C–– Efficiency
C–– allows top-level control code to be written in a C-like language. It does
have limitations though. Assembly routines are needed to support C function
calls for operations such as reading/writing ports and speaking. The assembly
code produced by the C–– compiler is not optimized and will not be as efficient
as hand written assembly. Because C–– is not optimized, time critical
operations should always be written in assembly.
Since the compiler does not optimize the assembly, writing C–– code in
different ways results in different levels of overhead. While and do-while loops
have similar overhead (one conditional jump and 1 unconditional jump per