Zilog Z80380 Manual de usuario descargar pdf (Pagina 43)

UM004001-COR1103 2–9

C-Compiler Overview Optimization Levels

OPTIMIZATION LEVELS

The Z380 C-compiler allows the user to manually specify the level of optimization they want

to have performed on their code. The optimization levels are controlled through the C-com

piler options dialog box. See Configuring Optimization Levels on page 1-15 for more infor-

mation on the C-compiler Settings Option dialog box.

The Z380 C-compiler allows you to specify four levels of optimizations. The optimizations

are:

• Level 1 optimization

– constant folding

– dead object removal

– simple jump optimization

• Level 2 optimization

– constant propagation

– copy propagation

– dead-code elimination

– common sub-expression elimination

– jump-to-jump optimization

– loop invariant code motion

– constant condition evaluation and other condition evaluation optimizations

– constant evaluation and expression simplification

– all the optimizations in level 1

• Check Level 3 optimization to perform Level 2 optimizations twice, and replace any

redirection of read-only nonvolatile global or static data with a copy of its initial

expression.

• Check Level 4 optimization to perform Level 2 optimizations three times, and

eliminate common sub-expressions by transforming of expression trees.

DEBUGGING CODE AFTER OPTIMIZATION

Debugging of code should be complete before performing any level of optimization on the

code. If the generate debug information is on no optimizations are performed, even if an opti

mization level is chosen.

NOTE: To enable or disable debug information in ZDS select Settings from the Options menu. Click

the

Linker tab and select Output from the Category pop-up list.

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Zilog Z80380 Manual de usuario Pagina 43