riscv64,exec: add fence.i

src/isa/riscv64/exec/all-instr.h

@@ -25,6 +25,7 @@ make_EHelper(bne);
 
 make_EHelper(inv);
 make_EHelper(nemu_trap);
+make_EHelper(fence);
 
 make_EHelper(csrrw);
 make_EHelper(csrrs);

src/isa/riscv64/exec/exec.c

@@ -65,7 +65,7 @@ static make_EHelper(system) {
 }
 
 static OpcodeEntry opcode_table [32] = {
-  /* b00 */ IDEX(ld, load), EMPTY, EMPTY, EMPTY, IDEX(I, op_imm), IDEX(U, auipc), IDEX(I, op_imm32), EMPTY,
+  /* b00 */ IDEX(ld, load), EMPTY, EMPTY, EX(fence), IDEX(I, op_imm), IDEX(U, auipc), IDEX(I, op_imm32), EMPTY,
   /* b01 */ IDEX(st, store), EMPTY, EMPTY, EMPTY, IDEX(R, op), IDEX(U, lui), IDEX(R, op32), EMPTY,
   /* b10 */ EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY, EMPTY,
   /* b11 */ IDEX(B, branch), IDEX(I, jalr), EX(nemu_trap), IDEX(J, jal), EX(system), EMPTY, EMPTY, EMPTY,

src/isa/riscv64/exec/special.c

@@ -27,3 +27,5 @@ make_EHelper(nemu_trap) {
   print_asm("nemu trap");
   return;
 }
+
+make_EHelper(fence) { }