Renesas Technology, Tools FAQs
Last Updated: August 7, 2000
Document Number: 01051009_e
Q.
When optimization option "-ONSBD" is specified, what kind of de-optimization happens?
A.
The following de-optimizations are performed:
- Common statement expressions are merged (so that the same statement expressions will not be calculated repeatedly)
●
- Common instruction blocks are bound together (repetitive instructions are replaced by branches)●
- Multiple byte-store operations to sequential addresses are converted to word-store operations●
- Sequential constant byte-push operations are converted to word-push operations●
- Continuous shift operations are bound together (bind "b=a<<2; b<<=2;" to "b=a<<4", etc.)●
- Bit operations are grouped into OR, AND operations●
- 'for' statement loop condition check is moved to the end of the loop to reduce redundant loop compare operations●
- Unconditional branch to "return" statement is replaced with "return" statement (NC308 only)●
- Multiply/division by multiples of 2 is replaced to shift operation●
- Auto variables is assigned to register●
- Constants are folded in●
* Note that these optimizations may not be performed depending on pre and post statements.
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