src/soc/decoder/helpers.py

   1 import unittest
   2 def exts(value, bits):
   3     sign = 1 << (bits - 1)
   4     return (value & (sign - 1)) - (value & sign)
   5
   6 def EXTS64(value):
   7     return exts(value, 32) & ((1<<64)-1)
   8
   9 def EXTZ64(value):
  10     return value & ((1<<32)-1)
  11
  12 def rotl(value, bits, wordlen):
  13     mask = (1 << wordlen) - 1
  14     bits = bits & (wordlen - 1)
  15     return ((value << bits) | (value >> (wordlen-bits))) & mask
  16
  17 def ROTL64(value, bits):
  18     return rotl(value, bits, 64)
  19
  20 def ROTL32(value, bits):
  21     return rotl(value, bits, 32)
  22
  23 def MASK(x, y):
  24     if x < y:
  25         x = 64-x
  26         y = 63-y
  27         mask_a = ((1<<x) - 1) & ((1<<64) - 1)
  28         mask_b = ((1<<y) - 1) & ((1<<64) - 1)
  29     else:
  30         x = 64-x
  31         y = 63-y
  32         mask_a = ((1<<x) - 1) & ((1<<64) - 1)
  33         mask_b = (~((1<<y) - 1)) & ((1<<64) - 1)
  34     return mask_a ^ mask_b
  35
  36
  37 # For these tests I tried to find power instructions that would let me
  38 # isolate each of these helper operations. So for instance, when I was
  39 # testing the MASK() function, I chose rlwinm and rldicl because if I
  40 # set the shift equal to 0 and passed in a value of all ones, the
  41 # result I got would be exactly the same as the output of MASK()
  42
  43 class HelperTests(unittest.TestCase):
  44     def test_MASK(self):
  45         # Verified using rlwinm, rldicl, rldicr in qemu
  46         # li 1, -1
  47         # rlwinm reg, 1, 0, 5, 15
  48         self.assertHex(MASK(5+32, 15+32), 0x7ff0000)
  49         # rlwinm reg, 1, 0, 15, 5
  50         self.assertHex(MASK(15+32, 5+32), 0xfffffffffc01ffff)
  51         self.assertHex(MASK(30+32, 2+32), 0xffffffffe0000003)
  52         # rldicl reg, 1, 0, 37
  53         self.assertHex(MASK(37, 63), 0x7ffffff)
  54         self.assertHex(MASK(10, 63), 0x3fffffffffffff)
  55         self.assertHex(MASK(58, 63), 0x3f)
  56         # rldicr reg, 1, 0, 37
  57         self.assertHex(MASK(0, 37), 0xfffffffffc000000)
  58         self.assertHex(MASK(0, 10), 0xffe0000000000000)
  59         self.assertHex(MASK(0, 58), 0xffffffffffffffe0)
  60
  61     def test_ROTL64(self):
  62         # r1 = 0xdeadbeef12345678
  63         value = 0xdeadbeef12345678
  64
  65         # rldicl reg, 1, 10, 0
  66         self.assertHex(ROTL64(value, 10), 0xb6fbbc48d159e37a)
  67         # rldicl reg, 1, 35, 0
  68         self.assertHex(ROTL64(value, 35), 0x91a2b3c6f56df778)
  69         self.assertHex(ROTL64(value, 58), 0xe37ab6fbbc48d159)
  70         self.assertHex(ROTL64(value, 22), 0xbbc48d159e37ab6f)
  71
  72     def test_ROTL32(self):
  73         # r1 = 0xdeadbeef
  74         value = 0xdeadbeef
  75
  76         # rlwinm reg, 1, 10, 0, 31
  77         self.assertHex(ROTL32(value, 10), 0xb6fbbf7a)
  78         # rlwinm reg, 1, 17, 0, 31
  79         self.assertHex(ROTL32(value, 17), 0x7ddfbd5b)
  80         self.assertHex(ROTL32(value, 25), 0xdfbd5b7d)
  81         self.assertHex(ROTL32(value, 30), 0xf7ab6fbb)
  82
  83     def test_EXTS64(self):
  84         value_a = 0xdeadbeef # r1
  85         value_b = 0x73123456 # r2
  86         value_c = 0x80000000 # r3
  87
  88         # extswsli reg, 1, 0
  89         self.assertHex(EXTS64(value_a), 0xffffffffdeadbeef)
  90         # extswsli reg, 2, 0
  91         self.assertHex(EXTS64(value_b), value_b)
  92         # extswsli reg, 3, 0
  93         self.assertHex(EXTS64(value_c), 0xffffffff80000000)
  94
  95
  96
  97     def assertHex(self, a, b):
  98         msg = "{:x} != {:x}".format(a, b)
  99         return self.assertEqual(a, b, msg)
 100
 101 if __name__ == '__main__':
 102     unittest.main()