Simple ppc64/ppc64le generated machine code example that's a little more complicated

jitlab2.c

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <inttypes.h>
#include <sys/mman.h>
#include <sys/syscall.h>
#include <linux/memfd.h>

uint32_t* jitcode;
uint32_t* jitcode_x;
int (*calljit)(int);

// op comes right out of the PowerISA 3.0 documentation
#define IMM(op, regsd, rega, imm)            (uint32_t)(((op)<<26)|((regsd)<<21)|((rega)<<16)|             (((imm))&0xFFFF))
#define DSF(op, regs, rega, ds, bb)          (uint32_t)(((op)<<26)|((regs) <<21)|((rega)<<16)|             (((ds))&0xFFFC)|(bb))
#define EXT(regsd, rega, regb, op, rc)       (uint32_t)(  (31<<26)|((regsd)<<21)|((rega)<<16)| ((regb)<<11)|                       ((op)<<1)              |(rc))
#define RLW(op, regs, rega, sh, mb, me, rc)  (uint32_t)(((op)<<26)|((regs) <<21)|((rega)<<16)|   ((sh)<<11)|((mb   )<<6)|((me)<<1)                        |(rc))
#define RLD(op, regs, rega, sh, mx, opb, rc) (uint32_t)(((op)<<26)|((regs) <<21)|((rega)<<16)|((sh&31)<<11)|((mx&31)<<6)|(mx&32)  |((opb)<<2)|((sh&32)>>4)|(rc))

static int printint(int x) { fprintf(stdout, "called with %d\n", x); return x; }

int main(int argc, char** argv) {
	int fd, rv = 0;
	size_t pagesize;
	uint64_t f;

	pagesize = sysconf(_SC_PAGE_SIZE);
	fd = syscall(__NR_memfd_create, "jitlab", MFD_CLOEXEC);
	ftruncate(fd, pagesize);
	jitcode = (uint32_t*)mmap(NULL, pagesize,
		PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);

	f = (uint64_t)&printint;
	jitcode[0]  = DSF(62,  1,  1, -256, 1); // stdu 1,-256(1)
	jitcode[1]  = EXT(0, 8, 0, 339, 0); // mflr 0

	jitcode[2]  = IMM(15, 12,  0, (f & 0xffff000000000000)>>48); // lis
	jitcode[3]  = IMM(24, 12, 12, (f & 0x0000ffff00000000)>>32); // ori
	jitcode[4]  = RLD(30, 12, 12, 32, 31, 1, 0); // rldicr 12,12,32,31
	jitcode[5]  = IMM(25, 12, 12, (f & 0x00000000ffff0000)>>16); // oris
	jitcode[6]  = IMM(24, 12, 12, (f & 0x000000000000ffff)    ); // ori

	jitcode[7]  = EXT(12, 9, 0, 467, 0); // mtctr 12
	jitcode[8]  = IMM(14,  3,  3, 2020);   // addi 3, 3, 2020
	jitcode[9]  = DSF(62,  0,  1, 272, 0); // std 0,272(1)
	jitcode[10] = IMM(19, 20,  0, (528<<1)|1); // bctrl

	jitcode[11] = DSF(58,  0,  1, 272, 0); // ld 0,272(1)
	jitcode[12] = EXT(0, 8, 0, 467, 0); // mtlr 0
	jitcode[13] = EXT(3, 3, 3, 266, 0); // add 3,3,3
	jitcode[14] = IMM(14,  1,  1, 256); // addi 1,1,256
	jitcode[15] = IMM(19, 20, 0, 32); // blr

	fprintf(stdout, "jitcode at 0x%llx\n", (uint64_t)jitcode);
	asm volatile(
		"dcbst %y0\n"
		"sync\n"
		"icbi %y0\n"
		"isync\n"
	:: "Z"(*jitcode));

	jitcode_x = (uint32_t*)mmap(NULL, pagesize,
		PROT_READ|PROT_EXEC, MAP_SHARED, fd, 0);
	calljit = (int (*)(int))jitcode_x;
	rv = calljit(1111);

	fprintf(stdout, "result = %d\n", rv);
	munmap(jitcode, pagesize);
	munmap(jitcode_x, pagesize);
	close(fd);
	return 0;
}