how to use the floating point hardware in nios II custom instructions

hi mikedsouze, thanks for your help.

i check the objdump file, i find it is a little like a assembly language file.

when i add the floating point hardware in nios II, i use both

c=a*b

and

c=ALT_CI_NIOS_CUSTOM_INSTR_FLOATING_POINT_0(0,a,b);

then i check the objdump file:

c=a*b;

1082c4: e13ffc17 ldw r4,-16(fp)

1082c8: e17ffd17 ldw r5,-12(fp)

1082cc: 01084140 call 108414 <__mulsf3>

1082d0: 1007883a mov r3,r2

1082d4: e0fffe15 stw r3,-8(fp)

c=ALT_CI_NIOS_CUSTOM_INSTR_FLOATING_POINT_0(0,b,a);

1083d8: e13ffd17 ldw r4,-12(fp)

1083dc: 0108d340 call 108d34 <__fixsfsi>

1083e0: 1021883a mov r16,r2

1083e4: e13ffc17 ldw r4,-16(fp)

1083e8: 0108d340 call 108d34 <__fixsfsi>

1083ec: 8085ff32 custom 252,r2,r16,r2

1083f0: 1009883a mov r4,r2

1083f4: 0108dac0 call 108dac <__floatsisf>

1083f8: 1007883a mov r3,r2

1083fc: e0fffe15 stw r3,-8(fp)

it looks like the floating point hardware will only be used when i use

c=ALT_CI_NIOS_CUSTOM_INSTR_FLOATING_POINT_0(0,b,a);

but when run debug, the result of the c=ALT_CI_NIOS_CUSTOM_INSTR_FLOATING_POINT_0(0,b,a); is 0.0