компилятор C и C ++ проекта GNU (GNU project C and C++ compiler)
Параметры подробно (Options detail)
Adapteva Epiphany
These -m options are defined for Adapteva Epiphany:
-mhalf-reg-file
Don't allocate any register in the range "r32"..."r63". That
allows code to run on hardware variants that lack these
registers.
-mprefer-short-insn-regs
Preferentially allocate registers that allow short
instruction generation. This can result in increased
instruction count, so this may either reduce or increase
overall code size.
-mbranch-cost=num
Set the cost of branches to roughly num "simple"
instructions. This cost is only a heuristic and is not
guaranteed to produce consistent results across releases.
-mcmove
Enable the generation of conditional moves.
-mnops=num
Emit num NOPs before every other generated instruction.
-mno-soft-cmpsf
For single-precision floating-point comparisons, emit an
"fsub" instruction and test the flags. This is faster than a
software comparison, but can get incorrect results in the
presence of NaNs, or when two different small numbers are
compared such that their difference is calculated as zero.
The default is -msoft-cmpsf, which uses slower, but IEEE-
compliant, software comparisons.
-mstack-offset=num
Set the offset between the top of the stack and the stack
pointer. E.g., a value of 8 means that the eight bytes in
the range "sp+0...sp+7" can be used by leaf functions without
stack allocation. Values other than 8 or 16 are untested and
unlikely to work. Note also that this option changes the
ABI; compiling a program with a different stack offset than
the libraries have been compiled with generally does not
work. This option can be useful if you want to evaluate if a
different stack offset would give you better code, but to
actually use a different stack offset to build working
programs, it is recommended to configure the toolchain with
the appropriate --with-stack-offset=num option.
-mno-round-nearest
Make the scheduler assume that the rounding mode has been set
to truncating. The default is -mround-nearest.
-mlong-calls
If not otherwise specified by an attribute, assume all calls
might be beyond the offset range of the "b" / "bl"
instructions, and therefore load the function address into a
register before performing a (otherwise direct) call. This
is the default.
-mshort-calls
If not otherwise specified by an attribute, assume all direct
calls are in the range of the "b" / "bl" instructions, so use
these instructions for direct calls. The default is
-mlong-calls.
-msmall16
Assume addresses can be loaded as 16-bit unsigned values.
This does not apply to function addresses for which
-mlong-calls semantics are in effect.
-mfp-mode=mode
Set the prevailing mode of the floating-point unit. This
determines the floating-point mode that is provided and
expected at function call and return time. Making this mode
match the mode you predominantly need at function start can
make your programs smaller and faster by avoiding unnecessary
mode switches.
mode can be set to one the following values:
caller
Any mode at function entry is valid, and retained or
restored when the function returns, and when it calls
other functions. This mode is useful for compiling
libraries or other compilation units you might want to
incorporate into different programs with different
prevailing FPU modes, and the convenience of being able
to use a single object file outweighs the size and speed
overhead for any extra mode switching that might be
needed, compared with what would be needed with a more
specific choice of prevailing FPU mode.
truncate
This is the mode used for floating-point calculations
with truncating (i.e. round towards zero) rounding mode.
That includes conversion from floating point to integer.
round-nearest
This is the mode used for floating-point calculations
with round-to-nearest-or-even rounding mode.
int This is the mode used to perform integer calculations in
the FPU, e.g. integer multiply, or integer multiply-and-
accumulate.
The default is -mfp-mode=caller
-mno-split-lohi
-mno-postinc
-mno-postmodify
Code generation tweaks that disable, respectively, splitting
of 32-bit loads, generation of post-increment addresses, and
generation of post-modify addresses. The defaults are
msplit-lohi, -mpost-inc, and -mpost-modify.
-mnovect-double
Change the preferred SIMD mode to SImode. The default is
-mvect-double, which uses DImode as preferred SIMD mode.
-max-vect-align=num
The maximum alignment for SIMD vector mode types. num may be
4 or 8. The default is 8. Note that this is an ABI change,
even though many library function interfaces are unaffected
if they don't use SIMD vector modes in places that affect
size and/or alignment of relevant types.
-msplit-vecmove-early
Split vector moves into single word moves before reload. In
theory this can give better register allocation, but so far
the reverse seems to be generally the case.
-m1reg-reg
Specify a register to hold the constant -1, which makes
loading small negative constants and certain bitmasks faster.
Allowable values for reg are r43 and r63, which specify use
of that register as a fixed register, and none, which means
that no register is used for this purpose. The default is
-m1reg-none.
