Intel i960 - Page 64

i960 Processor Compiler User's Guide
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2
O2 This level includes the O or O1 optimizations
described above, and the following additional
optimizations:
fcopyprop, fcondxform, fcse-follow-
jumps
, fcse-skip-blocks, fexpensive-
optimizations
, frerun-cse-after-loop,
fschedule-insns, fschedule-insns2,
fshadow-globals, fstrength-reduce.
The
O2 level enables strength-reduction,
combination of more than one variable value into
a single register, copy propagation, tail-call
elimination, leaf-procedure optimization, and
instruction reordering (scheduling) to make use
of the particular i960 processor's pipeline and
superscalar capabilities.
O3 This level includes the O2 optimizations
described above, and the following additional
optimizations:
fcoerce, fconstprop, finline-functions,
fshadow-mem, funroll-loops.
O4 This level includes the O3 optimizations
described above, and the following additional
optimizations:
fcoalesce, fmarry_mem, fsplit_mem.
O5 This setting specifies program-wide
optimization. Before using the
O5 option, you
should read Chapter 4, Program-wide Analysis
and Optimization, and Chapter 6, gcdm Decision
Maker Option.
Note that the
O5 level is not accepted directly by
the gcc960 driver. It is accepted only in the
subst argument of the gcdm option.