3.18.37 PDP-11 Options
These options are defined for the PDP-11:
- -mfpu
-  Use hardware FPP floating point. This is the default. (FIS floating point on the PDP-11/40 is not supported.) Implies -m45. 
- -msoft-float
-  Do not use hardware floating point. 
- -mac0
-  Return floating-point results in ac0 (fr0 in Unix assembler syntax). 
- -mno-ac0
-  Return floating-point results in memory. This is the default. 
- -m40
-  Generate code for a PDP-11/40. Implies -msoft-float -mno-split. 
- -m45
-  Generate code for a PDP-11/45. This is the default. 
- -m10
-  Generate code for a PDP-11/10. Implies -msoft-float -mno-split. 
- -mint16
- -mno-int32
-   Use 16-bit int. This is the default.
- -mint32
- -mno-int16
-   Use 32-bit int.
- -msplit
-  Target has split instruction and data space. Implies -m45. 
- -munix-asm
-  Use Unix assembler syntax. 
- -mdec-asm
-  Use DEC assembler syntax. 
- -mgnu-asm
-  Use GNU assembler syntax. This is the default. 
- -mlra
-  Use the new LRA register allocator. By default, the old “reload” allocator is used. 
    © Free Software Foundation
Licensed under the GNU Free Documentation License, Version 1.3.
    https://gcc.gnu.org/onlinedocs/gcc-9.3.0/gcc/PDP_002d11-Options.html