Remove N extension

This extension was never ratified, has been removed from the ISA manual and apparently would need significant changes if it were to ever come back.

Therefore it makes sense to remove it from the model in order to simplify the code.

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_next.sail riscv_insts_hints.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_fext.sail riscv_insts_zcf.sail
 SAIL_DEFAULT_INST += riscv_insts_dext.sail riscv_insts_zcd.sail
 
@@ -72,10 +72,8 @@ SAIL_RMEM_INST_SRCS = riscv_insts_begin.sail $(SAIL_RMEM_INST) riscv_insts_end.s
 # System and platform sources
 SAIL_SYS_SRCS =  riscv_csr_begin.sail       # Start of CSR scattered definitions.
 SAIL_SYS_SRCS += riscv_vext_control.sail    # helpers for the 'V' extension
-SAIL_SYS_SRCS += riscv_next_regs.sail
 SAIL_SYS_SRCS += riscv_sys_exceptions.sail  # default basic helpers for exception handling
 SAIL_SYS_SRCS += riscv_sync_exception.sail  # define the exception structure used in the model
-SAIL_SYS_SRCS += riscv_next_control.sail    # helpers for the 'N' extension
 SAIL_SYS_SRCS += riscv_softfloat_interface.sail riscv_fdext_regs.sail riscv_fdext_control.sail
 SAIL_SYS_SRCS += riscv_sys_control.sail     # general exception handling
 

model/riscv_csr_begin.sail

@@ -15,16 +15,6 @@ scattered mapping csr_name_map
 // TODO: These csr_name_map definitions should be moved to the files
 // corresponding to their extensions rather than all be here.
 
-/* user trap setup */
-mapping clause csr_name_map = 0x000  <-> "ustatus"
-mapping clause csr_name_map = 0x004  <-> "uie"
-mapping clause csr_name_map = 0x005  <-> "utvec"
-/* user trap handling */
-mapping clause csr_name_map = 0x040  <-> "uscratch"
-mapping clause csr_name_map = 0x041  <-> "uepc"
-mapping clause csr_name_map = 0x042  <-> "ucause"
-mapping clause csr_name_map = 0x043  <-> "utval"
-mapping clause csr_name_map = 0x044  <-> "uip"
 /* user floating-point context */
 mapping clause csr_name_map = 0x001  <-> "fflags"
 mapping clause csr_name_map = 0x002  <-> "frm"
@@ -100,8 +90,6 @@ mapping clause csr_name_map = 0xC9F  <-> "hpmcounter31h"
 
 /* supervisor trap setup */
 mapping clause csr_name_map = 0x100  <-> "sstatus"
-mapping clause csr_name_map = 0x102  <-> "sedeleg"
-mapping clause csr_name_map = 0x103  <-> "sideleg"
 mapping clause csr_name_map = 0x104  <-> "sie"
 mapping clause csr_name_map = 0x105  <-> "stvec"
 mapping clause csr_name_map = 0x106  <-> "scounteren"

model/riscv_insts_zicsr.sail

@@ -74,8 +74,6 @@ function clause read_CSR(0x7a0) = ~(tselect)  /* this indicates we don't have an
 
 /* supervisor mode */
 function clause read_CSR(0x100) = lower_mstatus(mstatus).bits
-function clause read_CSR(0x102) = sedeleg.bits
-function clause read_CSR(0x103) = sideleg.bits
 function clause read_CSR(0x104) = lower_mie(mie, mideleg).bits
 function clause read_CSR(0x105) = get_stvec()
 function clause read_CSR(0x106) = zero_extend(scounteren.bits)
@@ -162,8 +160,6 @@ function clause write_CSR(0x7a0, value) = { tselect = value; tselect }
 
 /* supervisor mode */
 function clause write_CSR(0x100, value) = { mstatus = legalize_sstatus(mstatus, value); mstatus.bits }
-function clause write_CSR(0x102, value) = { sedeleg = legalize_sedeleg(sedeleg, value); sedeleg.bits }
-function clause write_CSR(0x103, value) = { sideleg.bits = value; sideleg.bits } /* TODO: does this need legalization? */
 function clause write_CSR(0x104, value) = { mie = legalize_sie(mie, mideleg, value); mie.bits }
 function clause write_CSR(0x105, value) = { set_stvec(value) }
 function clause write_CSR(0x106, value) = { scounteren = legalize_scounteren(scounteren, value); zero_extend(scounteren.bits) }