#!/usr/bin/python3
##################################
# testgen-TVEC.py (new)
#
# dottolia@hmc.edu 1 Mar 2021
#
# Generate directed and random test vectors for RISC-V Design Validation.
#
#
##################################
# DOCUMENTATION:
#
# The most up-to-date comments explaining what everything
# does and the layout of the privileged tests
# can be found in testgen-TVAL.py. This and
# other files do not have as many comments
#
###################################

##################################
# libraries
##################################
from datetime import datetime
from random import randint 
from random import seed
from random import getrandbits

##################################
# setup
##################################

areVectoredTrapsSupported = True

##################################
# functions
##################################

#For instruction-fetch access or page-fault exceptions on systems with variable-length instructions, mtval will contain the virtual address of the portion of the instruction that caused the fault while mepc will point to the beginning of the instruction.

def randRegs():
  reg1 = randint(1,20)
  reg2 = randint(1,20)
  reg3 = randint(1,20)
  if (reg1 == 6 or reg2 == 6 or reg3 == 6 or reg1 == reg2):
    return randRegs()
  else:
      return str(reg1), str(reg2), str(reg3)

def writeVectors(storecmd, returningInstruction):
  global testnum


  # Illegal Instruction 
  # writeTest(storecmd, f, r, f"""
  #   .fill 1, 4, 0
  # """, False, 0)

  # # Breakpoint
  # if returningInstruction != "ebreak":
  #   writeTest(storecmd, f, r, f"""
  #     ebreak
  #   """, False, 0)

  # # Load Address Misaligned 
  # writeTest(storecmd, f, r, f"""
  #   lw x0, 11(x0)
  # """, False, 0)

  # # Load Access fault: False, 5

  # # Store/AMO address misaligned
  # writeTest(storecmd, f, r, f"""
  #   sw x0, 11(x0)
  # """, False, 0)

  # # Environment call from u-mode: only for when only M and U mode enabled?
  # # writeTest(storecmd, f, r, f"""
  # #   ecall
  # # """, False, 8, "u")
  if returningInstruction != "ecall":
    writeTest(storecmd, f, r, f"""
      ecall
    """, False, 0)


  if fromMode == "m" and testMode == "m":
    expectedCode = 7 if fromMode == "m" else 5
    clintAddr = "0x2004000"

    writeTest(storecmd, f, r, f"""
      li x1, 0x8
      csrrs x0, {fromMode}status, x1

      la x18, {clintAddr}
      # lw x11, 0(x18)
      # li x1, 0x3fffffffffffffff
      # {storecmd} x1, 0(x18)

      li x1, 0x80
      csrrs x0, {fromMode}ie, x1

      {storecmd} x0, 0(x18)
    """, True, expectedCode, f"""
      li x1, 0x80
      csrrc x0, {fromMode}ie, x1

      li x1, 0x8
      csrrc x0, {fromMode}status, x1

      la x18, {clintAddr}
      {storecmd} x0, 0(x18)
    """)

  # Instruction page fault: 12
  # Load page fault: 13
  # Store/AMO page fault: 15
  

  

def writeTest(storecmd, f, r, test, interrupt, code, resetHander = ""):
  global testnum, storeAddressOffset, xlen

  expected = code

  # Boilerplate
  #
  # x28 is the address that our trap handler will jump to before returning.
  # This is where we can do our actual tests. After we're done computing and storing
  # what we want, we jump to x27, which continues with the trap handling code (look at the _j_x_trap_... labels)
  # 
  lines = f"""
    la x28, _jtest{testnum}
    j _jdo{testnum}

    _jtest{testnum}:
    nop
    {resetHander}
    jr x27

    _jdo{testnum}:
    li x25, 0xDEADBEA7
    {test}
  """


  if not areVectoredTrapsSupported or not vectoredInterrupts:
    expected = 0

  writeGeneralTest(storecmd, f, r, lines, expected)

def writeGeneralTest(storecmd, f, r, test, expected):
  global testnum, storeAddressOffset, xlen

  lines = f"""
    {test}
    {storecmd} x25, {testnum * wordsize}(x6)
  """

  f.write(lines)
  if (xlen == 32):
    line = formatrefstr.format(expected)+"\n"
  else:
    line = formatrefstr.format(expected % 2**32)+"\n" + formatrefstr.format(expected >> 32) + "\n"
  r.write(line)

  testnum = testnum+1

##################################
# main body
##################################

author = "dottolia@hmc.edu"
xlens = [32, 64]
testCount = 4;

# setup
# Change this seed to a different constant value for every test
seed(0xC363DAEB9193AB45) # make tests reproducible

# generate files for each test
for xlen in xlens:
  formatstrlen = str(int(xlen/4))
  formatstr = "0x{:0" + formatstrlen + "x}" # format as xlen-bit hexadecimal number
  formatrefstr = "{:08x}" # format as xlen-bit hexadecimal number with no leading 0x
  if (xlen == 32):
    storecmd = "sw"
    wordsize = 4
  else:
    storecmd = "sd"
    wordsize = 8

  # testMode can be m, s, and u. User mode traps are deprecated, so this should likely just be ["m", "s"]
  for testMode in ["m", "s"]:
    imperaspath = "../../../imperas-riscv-tests/riscv-test-suite/rv" + str(xlen) + "p/"
    basename = "WALLY-" + testMode.upper() + "TVEC"
    fname = imperaspath + "src/" + basename + ".S"
    refname = imperaspath + "references/" + basename + ".reference_output"
    testnum = 0
    storeAddressOffset = 0

    # print custom header part
    f = open(fname, "w")
    r = open(refname, "w")
    line = "///////////////////////////////////////////\n"
    f.write(line)
    lines="// "+fname+ "\n// " + author + "\n"
    f.write(lines)
    line ="// Created " + str(datetime.now()) 
    f.write(line)

    # insert generic header
    h = open("../testgen_header.S", "r")
    for line in h:  
      f.write(line)

    # Ensure MODE of *tvec (last 2 bits) is either 00 or 01
    f.write(f"""
      csrr x19, {testMode}tvec
    """)

    for i in range(0, 16):
      i = i;
      trySet = i | 0b10;
      expected = trySet & 0xFFFF_FFFFD;
      writeGeneralTest(storecmd, f, r, f"""
        li x1, {trySet}
        csrw {testMode}tvec, x1
        csrr x25, {testMode}tvec
      """, expected)

    f.write(f"""
      csrw {testMode}tvec, x19
    """)

    # We need to leave at least one bit in medeleg unset so that we have a way to get
    # back to machine mode when the tests are complete (otherwise we'll only ever be able
    # to get up to supervisor mode). 
    #
    # So, we define a returning instruction which will be used to cause the exception that
    # brings us into machine mode. The bit for this returning instruction is NOT set in
    # medeleg. However, this also means that we can't test that instruction. So, we have
    # two different returning instructions.
    #
    # Current code is written to only support ebreak and ecall.
    #
    # For testgen-TVAL, we don't need to test ebreak, so we can use that as the sole
    # returning instruction. For others, like testgen-CAUSE, we'll need to put
    # both ebreak and ecall here.


    for returningInstruction in ["ebreak"]:
      for vectoredInterrupts in [True, False]:

        # All registers used:
        # x30: set to 1 if we should return to & stay in machine mode after trap, 0 otherwise
        # ...
        # x28: address trap handler should jump to for the test
        # x27: address the test should return to after the test
        # ...
        # x25: value to write to memory
        # ...
        # x20: intermediate value in trap handler. Don't overwrite this!
        # x19: mtvec old value
        # x18: medeleg old value
        # x17: sedeleg old value (currently unused — user mode traps deprecated)
        # x16: mideleg old value
        # ...
        # x10 - x14 can be freely written
        # ...
        # x7: copy of x6. Increment this instead of using an offset on x6.
        #     this allows us to create more than 2048/wordlen tests.
        #     This is the address we write results to
        # x6: Starting address we should write expected results to
        # ...
        # x1 - x5 can be freely written  



        # Set up x7 and store old value of mtvec
        lines = f"""
          # add x7, x6, x0
          csrr x19, mtvec
        """

        # Not used — user mode traps are deprecated
        if testMode == "u":
          lines += f"""
            csrr x17, sedeleg
            li x9, {"0b1100000000" if testMode == "u" else "0b0000000000"}
            csrs sedeleg, x9
            """

        # Code that will jump to the test (x28 is set in writeTest above)
        testJumpCode = f"""
          auipc x27, 0
          addi x27, x27, 12
          jr x28
        """

        beforeCode = {"m": "", "s": ""}
        for pm in ["m", "s"]:
          for i in range(0, 16):
            beforeCode[pm] = beforeCode[pm] + f"""
              nop
              nop
              li x25, {i}
              j _j_{pm}_trap_end_{returningInstruction}_{vectoredInterrupts}
            """

        # Code for handling traps in different modes
        # Some comments are inside of the below strings (prefixed with a #, as you might expected)
        enableVectored = "addi x1, x1, 1" if vectoredInterrupts else ""

        lines += f"""
          # Reset x30 to 0 so we can run the tests. We'll set this to 1 when tests are completed so we stay in machine mode
          li x30, 0

          # Set up 
          la x1, _j_m_trap_{returningInstruction}_{vectoredInterrupts}
          {enableVectored} # enable/don't enable vectored interrupts
          csrw mtvec, x1
          la x1, _j_s_trap_{returningInstruction}_{vectoredInterrupts}
          {enableVectored} # enable/don't enable vectored interrupts
          csrw stvec, x1
          la x1, _j_u_trap_{returningInstruction}_{vectoredInterrupts}
          {enableVectored} # enable/don't enable vectored interrupts
          # csrw utvec, x1 # user mode traps are not supported

          # Start the tests!
          j _j_t_begin_{returningInstruction}_{vectoredInterrupts}

          # Machine mode traps
          _j_m_trap_{returningInstruction}_{vectoredInterrupts}:
          {beforeCode['m']}

          _j_m_trap_end_{returningInstruction}_{vectoredInterrupts}:
          {testJumpCode}

          csrrs x20, mepc, x0
          addi x20, x20, 4
          csrrw x0, mepc, x20
          bnez x30, _j_all_end_{returningInstruction}_{vectoredInterrupts}
          mret

          # Supervisor mode traps
          _j_s_trap_{returningInstruction}_{vectoredInterrupts}:
          {beforeCode['s']}

          _j_s_trap_end_{returningInstruction}_{vectoredInterrupts}:
          {testJumpCode}

          csrrs x20, sepc, x0
          addi x20, x20, 4
          csrrw x0, sepc, x20
          bnez x30, _j_goto_machine_mode_{returningInstruction}_{vectoredInterrupts}
          sret

          # Unused: user mode traps are no longer supported
          _j_u_trap_{returningInstruction}_{vectoredInterrupts}:
          {testJumpCode if testMode == "u" else "li x25, 0xBAD00000"}

          csrrs x20, uepc, x0
          addi x20, x20, 4
          csrrw x0, uepc, x20
          bnez x30, _j_goto_supervisor_mode_{returningInstruction}_{vectoredInterrupts}
          uret

          # Currently unused. Just jumps to _j_goto_machine_mode. If you actually
          # want to implement this, you'll likely need to reset sedeleg here
          # and then cause an exception with {returningInstruction} (based on my intuition. Try that first, but I could be missing something / just wrong)
          _j_goto_supervisor_mode_{returningInstruction}_{vectoredInterrupts}:
          j _j_goto_machine_mode_{returningInstruction}_{vectoredInterrupts}

          _j_goto_machine_mode_{returningInstruction}_{vectoredInterrupts}:
          li x30, 1 # This will cause us to branch to _j_all_end_{returningInstruction}_{vectoredInterrupts} in the machine trap handler, which we'll get into by invoking...
          {returningInstruction} # ... this instruction!

          # Run the actual tests!
          _j_t_begin_{returningInstruction}_{vectoredInterrupts}:
        """

        fromModeOptions = ["m", "s", "u"] if testMode == "m" else (["s", "u"] if testMode == "s" else ["u"])

        # We don't want to delegate our returning instruction. Otherwise, we'll have no way of getting
        # back to machine mode at the end! (and we need to be in machine mode to complete the tests)
        medelegMask = "0b1111111111110111" if returningInstruction == "ebreak" else "0b1111000011111111"

        # Set medeleg and mideleg
        lines += f"""
          csrr x18, medeleg
          li x9, {medelegMask if testMode == "s" or testMode == "u" else "0"}
          csrw medeleg, x9

          csrr x16, mideleg
          li x9, {"0xffffffff" if testMode == "s" or testMode == "u" else "0"}
          csrw mideleg, x9
        """

        f.write(lines)

        for fromMode in fromModeOptions:
          lines = ""
          
          # Code to bring us down to supervisor mode
          if fromMode == "s" or fromMode == "u":
            lines += f"""
              li x1, 0b110000000000
              csrrc x31, mstatus, x1
              li x1, 0b0100000000000
              csrrs x31, mstatus, x1

              auipc x1, 0
              addi x1, x1, 16 # x1 is now right after the mret instruction
              csrw mepc, x1
              mret

              # We're now in supervisor mode...
            """

          # Code to bring us down to user mode
          if fromMode == "u":
            lines += f"""

            li x1, 0b110000000000
            csrrc x31, sstatus, x1

            auipc x1, 0
            addi x1, x1, 16 # x1 is now right after the sret instruction
            csrw sepc, x1
            sret

            # We're now in user mode...
            """

          f.write(lines)
          for i in range(0,testCount):
            writeVectors(storecmd, returningInstruction)


        # Very end of test. Bring us back up to machine mode
        # We set x30 to 1, which will cause us to branch to _j_all_end in the
        # machine mode trap handler, before executing the mret instruction. This will
        # make us stay in machine mode.
        #
        # If we're currently in user mode, this will first bump us up to the supervisor mode
        # trap handler, which will call returningInstruction again before it's sret instruction,
        # bumping us up to machine mode
        #
        # Get into the trap handler by running returningInstruction (either an ecall or ebreak) 
        f.write(f"""
          li x30, 1
          li gp, 0
          {returningInstruction}
          _j_all_end_{returningInstruction}_{vectoredInterrupts}:

          # Reset trap handling csrs to old values
          csrw mtvec, x19
          csrw medeleg, x18
          csrw mideleg, x16
        """)

    # print footer
    h = open("../testgen_footer.S", "r")
    for line in h:  
      f.write(line)

    # Finish
    lines = ".fill " + str(testnum) + ", " + str(wordsize) + ", -1\n"
    lines = lines + "\nRV_COMPLIANCE_DATA_END\n" 
    f.write(lines)
    f.close()
    r.close()
