Zilog Z80380 - Manual (Page 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.
L EVEL 3 O PTIMIZATIONS
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.
L EVEL 4 O PTIMIZATIONS
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
E NABLING W ARNING M ESSAGES
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.