riscv custom instruction in inline assembly

gistfile1.txt

From https://groups.google.com/a/groups.riscv.org/d/msg/isa-dev/fONrcF2lxhQ/sb2ZN5Q_AQAJ

rohan:2183$ cat tmp.c 
int 
sub (int a, int b) 
{ 
  int result; 
  asm (".insn r 0x33, 0, 0, %0, %1, %2" : "=r" (result) : "r" (a), "r" (b)); 
  return result; 
} 
rohan:2184$ riscv32-unknown-elf-gcc -O2 -c tmp.c 
rohan:2185$ riscv32-unknown-elf-objdump -dr tmp.o 

tmp.o:     file format elf32-littleriscv 


Disassembly of section .text: 

00000000 <sub>: 
   0: 00b50533          add a0,a0,a1 
   4: 8082                ret 
rohan:2186$ 

Jim