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When you run GCC
, you can use command-line options to choose
machine-specific details. For information on all the GCC
command-line
options, see section `GNU CC Command Options' in Using GNU CC.
GCC options for architecture and code generation
-m1
- Generate code for the Hitachi SH-1 chip. This is the default
behavior for the Hitachi SH configuration.
-m2
- Generate code for the Hitachi SH-2 chip.
-m3
- Generate code for the Hitachi SH-3 chip.
-mfastcode
- Generate fast code, rather than small code.
-msmallcode
- Generate small code, rather than fast code.
-mnosave
- Use a different calling convention. The registers `R8', `R9',
`R10', and `R11' are all call-used with this setting
(see section Calling conventions).
-mhitachi
- Use Hitachi's calling convention rather than that for
GCC
. The
registers `MACH' and `MACL' are saved with this setting
(see section Calling conventions).
-mbsr
- Use
bsr
calls to code backward-referenced within the function.
Note: This may fail if the target is too far away.
-mshortaddr
- Assume that all static data fits into 16 bits, and keep pointers to them
in word-length rather than long-length pointers.
-mbigtable
- Generate jump tables for switch statements using four-byte offsets
rather than the standard two-byte offset. This option is necessary when
the code within a switch statement is larger that 32k. If the option is
needed and not supplied, the assembler will generate errors.
GCC options for floating point
Floating point subroutines
Two kinds of floating point subroutines are useful with GCC
:
-
Software implementations of the basic functions (floating-point
multiply, divide, add, subtract), for use when there is no hardware
floating-point support.
-
General-purpose mathematical subroutines.
The Developer's Kit from Cygnus Support includes an implementation of
the standard C mathematical subroutine library. See section `Mathematical Functions' in The Cygnus C Math Library.
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