Texas Instruments TMS320C2x, User Manual

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Performing Program-Level Optimization ( − pm and − o3 Options)
3-7 Optimizing Your Code
Table 3 − 4. Selecting a Level for the − op Option
If your module
…
Use this option
Has functions that are called from other modules and global vari-
ables that are modified in other modules − op0
Does not have functions that are called by other modules but has
global variables that are modified in other modules − op1
Does not have functions that are called by other modules or glob-
al variables that are modified in other modules − op2
Has functions that are called from other modules but does not
have global variables that are modified in other modules − op3
In certain circumstances, the compiler reverts to a different − op level from the
one you specified, or it might disable program-level optimization altogether.
Table 3
− 5 lists the combinations of − op levels and conditions that cause the
compiler to revert to other − op levels.
Table 3 − 5. Special Considerations When Using the − op Option
If your − op is... Under these conditions...
Then the − op
level...
Not specified The − o3 optimization level was specified Defaults to − op2
Not specified The compiler sees calls to outside functions
under the
− o3 optimization level
Reverts to − op0
Not specified Main is not defined Reverts to − op0
− op1 or − op2 No function has main defined as an entry
point Reverts to − op0
− op1 or − op2 No interrupt function is defined Reverts to − op0
− op1 or − op2 Functions are identified by the
FUNC_EXT_CALLED pragma Reverts to − op0
− op3 Any condition Remains − op3
In some situations when you use − pm and − o3, you must use an − op option
or the FUNC_EXT_CALLED pragma. See section 3.3.2, Optimization Consid-
erations When Mixing C and Assembly , on page 3-8 for information about
these situations.