Zilog Z80380 Bedienungsanleitung PDF herunterladen (Seite 45)

UM004001-COR1103 2–11

C-Compiler Overview Understanding errors

Jump to Jump Optimization

Targets in the control statement are replaced by the ultimate target.

Loop Invariant Code Motion

Expression within loops that compute the same value are identified and are replaced by a ref-

erence to a precomputed value.

Constant Condition Evaluation

The conditional expressions that are constant are computed at compile time.

Constant Evaluation and Expression Simplification

Replaces an expression by a simpler expression with the same semantics using constant fold-

ing, algebraic identities and tree transformations.

LEVEL 3 OPTIMIZATIONS

Level 3 optimization perform all the Level 2 optimizations twice, and replaces any redirec-

tion of read-only nonvolatile global or static data with a copy of its initial expression.

LEVEL 4 OPTIMIZATIONS

Level 4 optimization performs Level 2 optimizations three times, and eliminates common

sub-expressions by transforming of expression trees.

UNDERSTANDING ERRORS

The Z380 C-Compiler detects and reports errors in the source program. When an error is

encountered, an error message is displayed in the ZDS Output window.

For example:

“ file.c”, line n: error message

ENABLING WARNING MESSAGES

Warning messages can be disabled or enabled through the command line. See Table 2-2 for

more information on the various warnings that can be enabled.

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Zilog Z80380 Bedienungsanleitung Seite 45