Using and Porting GNU CC

3.14.11: Intel 386 Options

These `-m' options are defined for the i386 family of computers:

-m486

-mno-486

Control whether or not code is optimized for a 486 instead of an 386. Code generated for an 486 will run on a 386 and vice versa.

-msoft-float

Generate output containing library calls for floating point. Warning: the requisite libraries are not part of GNU CC. Normally the facilities of the machine's usual C compiler are used, but this can't be done directly in cross-compilation. You must make your own arrangements to provide suitable library functions for cross-compilation.

On machines where a function returns floating point results in the 80387 register stack, some floating point opcodes may be emitted even if `-msoft-float' is used.

-mno-fp-ret-in-387

Do not use the FPU registers for return values of functions.

The usual calling convention has functions return values of types float and double in an FPU register, even if there is no FPU. The idea is that the operating system should emulate an FPU.

The option `-mno-fp-ret-in-387' causes such values to be returned in ordinary CPU registers instead.

-mno-fancy-math-387

Some 387 emulators do not support the sin, cos and sqrt instructions for the 387. Specify this option to avoid generating those instructions. This option is the default on FreeBSD.