High-level optimizations exploit the properties of source code constructs (for example, loops and arrays) in the applications developed in high-level programming languages, such as Fortran and C++. The high-level optimizations include loop interchange, loop fusion, loop unrolling, loop distribution, unroll-and-jam, blocking, data prefetch, scalar replacement, data layout optimizations and loop unrolling techniques.
The option that turns on the high-level optimizations is -O3. See high-level language options summary. The scope of optimizations turned on by -O3 is different for IA-32 and Itanium(TM)-based applications. See Setting Optimization Levels.
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IA-32 and Itanium(TM)-based applications |
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-O3 |
Enable -O2 option plus more aggressive optimizations, for example, loop transformation and prefetching. -O3 optimizes for maximum speed, but may not improve performance for some programs. |
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IA-32 applications |
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-O3 |
In addition, in conjunction with the vectorization options, -ax{M|K|W} and -x{M|K|W}, -O3 causes the compiler to perform more aggressive data dependency analysis than for -O2. This may result in longer compilation times. |