separate zifencei extension

Makefile

@@ -21,7 +21,7 @@ SAIL_VLEN := riscv_vlen.sail
 
 # Instruction sources, depending on target
 SAIL_CHECK_SRCS = riscv_addr_checks_common.sail riscv_addr_checks.sail riscv_misa_ext.sail
-SAIL_DEFAULT_INST = riscv_insts_base.sail riscv_insts_aext.sail riscv_insts_zca.sail riscv_insts_mext.sail riscv_insts_zicsr.sail riscv_insts_hints.sail
+SAIL_DEFAULT_INST = riscv_insts_base.sail riscv_insts_zifencei.sail riscv_insts_aext.sail riscv_insts_zca.sail riscv_insts_mext.sail riscv_insts_zicsr.sail riscv_insts_hints.sail
 SAIL_DEFAULT_INST += riscv_insts_fext.sail riscv_insts_zcf.sail
 SAIL_DEFAULT_INST += riscv_insts_dext.sail riscv_insts_zcd.sail
 

model/riscv_insts_base.sail

@@ -607,17 +607,6 @@ function clause execute (FENCE_TSO(pred, succ)) = {
 mapping clause assembly = FENCE_TSO(pred, succ)
   <-> "fence.tso" ^ spc() ^ fence_bits(pred) ^ sep() ^ fence_bits(succ)
 
-/* ****************************************************************** */
-union clause ast = FENCEI : unit
-
-mapping clause encdec = FENCEI()
-  <-> 0b000000000000 @ 0b00000 @ 0b001 @ 0b00000 @ 0b0001111
-
-/* fence.i is a nop for the memory model */
-function clause execute FENCEI() = { /* __barrier(Barrier_RISCV_i); */ RETIRE_SUCCESS }
-
-mapping clause assembly = FENCEI() <-> "fence.i"
-
 /* ****************************************************************** */
 union clause ast = ECALL : unit
 

model/riscv_insts_zifencei.sail

@@ -0,0 +1,24 @@
+/*=======================================================================================*/
+/*  This Sail RISC-V architecture model, comprising all files and                        */
+/*  directories except where otherwise noted is subject the BSD                          */
+/*  two-clause license in the LICENSE file.                                              */
+/*                                                                                       */
+/*  SPDX-License-Identifier: BSD-2-Clause                                                */
+/*=======================================================================================*/
+
+/* ****************************************************************** */
+/* This file specifies the instructions in the 'Zifencei' extension.     */
+
+/* ****************************************************************** */
+enum clause extension = Ext_Zifencei
+function clause extensionEnabled(Ext_Zifencei) = true
+
+union clause ast = FENCEI : unit
+
+mapping clause encdec = FENCEI() if extensionEnabled(Ext_Zifencei)
+  <-> 0b000000000000 @ 0b00000 @ 0b001 @ 0b00000 @ 0b0001111 if extensionEnabled(Ext_Zifencei)
+
+/* fence.i is a nop for the memory model */
+function clause execute FENCEI() = { /* __barrier(Barrier_RISCV_i); */ RETIRE_SUCCESS }
+
+mapping clause assembly = FENCEI() <-> "fence.i"