What is N32?

What is N32?

N32 is a minor variation on the high performance 64-bit ABI. All the performance of the hardware is available to the program and existing 32-bit ABI programs are easily ported. Table 1-1 compares the various ABIs.

ABI Comparison Summary
o32 n32 n64
Compiler Used ucode MIPSpro MIPSpro
Integer Model ILP32 ILP32 LP64
Calling Convention mips new new
Number of FP Registers 16 (FR=0) 32 (FR=1) 32 (FR=1)
Number of Argument Registers 4 8 8
Debug Format mdbug dwarf dwarf
ISAs Supported mips1/2 mips3/4 mips3/4
32/64 Mode 32 (UX=0) 64 (UX=1) * 64 (UX=1)

ABI Comparison Summary
	o32	n32	n64
Compiler Used	ucode	MIPSpro	MIPSpro
Integer Model	ILP32	ILP32	LP64
Calling Convention	mips	new	new
Number of FP Registers	16 (FR=0)	32 (FR=1)	32 (FR=1)
Number of Argument Registers	4	8	8
Debug Format	mdbug	dwarf	dwarf
ISAs Supported	mips1/2	mips3/4	mips3/4
32/64 Mode	32 (UX=0)	64 (UX=1) *	64 (UX=1)

* UX=1 implies 64-bit registers and also indicates that MIPS3 and MIPS4 instructions are legal. N32 uses 64-bit registers but restricts addresses to 32 bits.