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Descriptions of options used by HP for CPU2000:
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-Ae		Enable ANSI compatibility mode with UNIX extensions.

-D		Set definition for preprocessor.

+DA<arch>	Generate code for the architecture specified.

+DS<arch>	Schedule code for the architecture specified.

+ESfic		Replace millicode calls with in-line code for 
		for indirect calls.

+ESlit		Put literals in read-only text space.

fastmem.o	Replacement for malloc/free that assumes ANSI compliant code.

+I/+P		Optimize/Instrument for profile based optimization.

-K		Use static storage for locals instead of stack storage. Same
		functionality as the +save option.  The default is +nosave.

+O1		Perform optimizations within basic blocks only.

+O2		Perform +O1 optimizations.  In addition perform global
		optimizations at the procedure level.  (Same as -O.)

+O3		Perform +O2 optimizations as well as interprocedural global
		optimizations within a file (including inlining).

+O4		Perform +O3 optimizations.  Also apply interprocedural
		optimizations across all files of the program.

+Oaggressive	Apply aggressive optimizations which include scheduling on
		procedure entry and exit code, replacing standard library
		calls with inlined code sequences, no auto-initialization
		of uninitialized local scalar non-static variables, and
		scheduling beyond basic block boundaries.

+Oall		Apply all optimizations that would be enabled by specifying
		+O4, +Oaggressive, and +Onolimit on the same command line.
		Detailed options countermanding components of +Oall override
		that component.

+Ocachepadcommon
		Pad common blocks to avoid cache collisions.

+Odataprefetch	Generate data prefetch instructions for data structures
		referenced within innermost loops.

+Oentrysched	Perform instruction scheduling on a subprogram's entry and
		exit sequences.

+O[no]fastaccess
		Enable [disable] fast access to global data items.

+O[no]fltacc	Disable [enable] optimizations that cause imprecise
		floating-point results.

+O[no]libcalls	Invoke [do not invoke] low call-overhead versions of
		select library routines.

+O[no]limit     Suppress [do not suppress] optimizations that
                significantly increase compile-time or consume
                enormous amounts of memory.  These optimizations
                can occur at levels 2, 3, and 4.  The default is +Olimit.

+O[no]loop_block
		Enable [disable] loopblocking for data cache optimizations.
		Available at optimization level 3 and above.

+O[no]loop_unroll
		Enable [disable] loop unrolling.

+Omultiprocessor
		Prevent instruction cache prefetching following subroutine 
		returns.  This can benefit some multithreaded applications.

+Optrs_strongly_typed 
		Assume that all pointers are type safe.

+Oregionsched	Perform scheduling across branches.

+Ostaticprediction
		Enable static branch prediction.

+O[no]vectorize	Replace eligible loops with calls to the vector library.

-Wl,+FPD	Enable sudden underflow (flush to zero) of denormalized 
		values.

-Wl,-a,archive	Link with archive format libraries rather than shared.