From: Jacob Lifshay Date: Wed, 11 Oct 2023 05:07:17 +0000 (-0700) Subject: WIP divmod: implemented division by single word X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=9ba191ba9958abaff0e9ebf977902396a48e6bb1;p=openpower-isa.git WIP divmod: implemented division by single word --- diff --git a/src/openpower/test/bigint/powmod.py b/src/openpower/test/bigint/powmod.py index a9653c54..6127b604 100644 --- a/src/openpower/test/bigint/powmod.py +++ b/src/openpower/test/bigint/powmod.py @@ -21,6 +21,9 @@ from nmutil.sim_util import hash_256 from openpower.util import log from nmutil.plain_data import plain_data from cached_property import cached_property +from openpower.decoder.isa.svshape import SVSHAPE +from openpower.decoder.power_enums import SPRfull +from openpower.decoder.selectable_int import SelectableInt MUL_256_X_256_TO_512_ASM = ( @@ -588,6 +591,10 @@ class DivModKnuthAlgorithmD: num_size = self.num_size denom_size = self.denom_size q_size = self.q_size + r_size = self.r_size + un_size = self.un_size + vn_size = self.vn_size + product_size = self.product_size yield "divmod_512_by_256:" # n in n_0 size num_size @@ -604,7 +611,61 @@ class DivModKnuthAlgorithmD: yield f"setvl 0, 0, {q_size}, 0, 1, 1" # set VL to q_size yield f"sv.addi *{q}, 0, 0" # q = [0] * q_size - raise NotImplementedError("FIXME: finish") + # get non-zero length of dividend + yield f"setvl 0, 0, {num_size}, 0, 1, 1" # set VL to num_size + # create SVSHAPE that reverses order + svshape = SVSHAPE(0) + svshape.zdimsz = num_size + svshape.invxyz = SelectableInt(0b1, 3) # invert Z + svshape_low = int(svshape) % 2 ** 16 + svshape_high = int(svshape) >> 16 + SVSHAPE0 = SPRfull.SVSHAPE0.value + yield f"addis 0, 0, {svshape_high}" + yield f"ori 0, 0, {svshape_low}" + yield f"mtspr {SVSHAPE0}, 0 # mtspr SVSHAPE0, 0" + yield f"svremap 0o01, 0, 0, 0, 0, 0, 0" # enable SVSHAPE0 for RA + yield f"sv.cmpi/ff=ne *0, 1, *{u}, 0" + yield f"setvl {m}, 0, 1, 0, 0, 0 # getvl {m}" # m = VL + yield f"subfic {m}, {m}, {num_size}" # m = num_size - m + + # get non-zero length of divisor + yield f"setvl 0, 0, {denom_size}, 0, 1, 1" # set VL to denom_size + # create SVSHAPE that reverses order + svshape = SVSHAPE(0) + svshape.zdimsz = denom_size + svshape.invxyz = SelectableInt(0b1, 3) # invert Z + svshape_low = int(svshape) % 2 ** 16 + svshape_high = int(svshape) >> 16 + yield f"addis 0, 0, {svshape_high}" + yield f"ori 0, 0, {svshape_low}" + yield f"mtspr {SVSHAPE0}, 0 # mtspr SVSHAPE0, 0" + yield f"svremap 0o01, 0, 0, 0, 0, 0, 0" # enable SVSHAPE0 for RA + yield f"sv.cmpi/ff=ne *0, 1, *{v}, 0" + yield f"setvl {n_scalar}, 0, 1, 0, 0, 0 # getvl {n_scalar}" # n = VL + # n = denom_size - n + yield f"subfic {n_scalar}, {n_scalar}, {denom_size}" + + yield f"cmpi 0, 1, {n_scalar}, 1 # cmpi {n_scalar}, 1" + yield "bc 4, 2, divmod_skip_sw_divisor # bne divmod_skip_sw_divisor" + + # Knuth's algorithm D requires the divisor to have length >= 2 + # handle single-word divisors separately + yield f"addi {t_single}, 0, 0" + yield f"setvl. {m}, {m}, {q_size}, 0, 1, 1" # m = VL = min(m, q_size) + # if CR0.SO: t = u[q_size] + yield f"sv.isel {t_single}, {u + q_size}, {t_single}, 3" + # div loop + yield f"sv.divmod2du/mrr *{q}, *{u}, {v}, {t_single}" + # r[0] = t + assert r == t_single, "r[0] and t_single must be in the same regs" + yield f"setvl 0, 0, {r_size - 1}, 0, 1, 1" # set VL to r_size - 1 + yield f"sv.addi *{r + 1}, 0, 0" # r[1:] = [0] * (r_size - 1) + + yield "bclr 20, 0, 0 # blr" + + yield "divmod_skip_sw_divisor:" + + # FIXME: finish yield "bclr 20, 0, 0 # blr" @cached_property @@ -738,6 +799,12 @@ class PowModCases(TestAccumulatorBase): yield (2 ** (256 - 1), 1) yield (2 ** (512 - 1) - 1, 2 ** 256 - 1) + # test division by single word + yield (((1 << 256) - 1) << 32, 1 << 32) + yield (((1 << 192) - 1) << 32, 1 << 32) + yield (((1 << 64) - 1) << 32, 1 << 32) + yield (1 << 32, 1 << 32) + # test qhat overflow yield (0x8000 << 128 | 0xFFFE << 64, 0x8000 << 64 | 0xFFFF) @@ -790,6 +857,40 @@ class PowModCases(TestAccumulatorBase): self.call_case( DIVMOD_SHIFT_SUB_512x256_TO_256x256_ASM, e, initial_regs) + def case_divmod_knuth_algorithm_d_512x256_to_256x256(self): + cases = list(self.divmod_512x256_to_256x256_test_inputs()) + asm = DivModKnuthAlgorithmD().asm + for n, d in cases: + if d >= 2 ** 64: + # FIXME: only single-word part of algorithm implemented, + # so we skip the ones that we expect to fail + continue + q, r = divmod(n, d) + with self.subTest(n=f"{n:#_x}", d=f"{d:#_x}", + q=f"{q:#_x}", r=f"{r:#_x}"): + # registers start filled with junk + initial_regs = [0xABCDEF] * 128 + for i in range(8): + # write n in LE order to regs 4-11 + initial_regs[4 + i] = (n >> (64 * i)) % 2**64 + for i in range(4): + # write d in LE order to regs 32-35 + initial_regs[32 + i] = (d >> (64 * i)) % 2**64 + # only check regs up to r11 since that's where the output is. + # don't check CR + e = ExpectedState(int_regs=initial_regs[:12], crregs=0) + e.intregs[0] = None # ignored + e.intregs[3] = None # ignored + e.ca = None # ignored + e.sprs['SVSHAPE0'] = None + for i in range(4): + # write q in LE order to regs 4-7 + e.intregs[4 + i] = (q >> (64 * i)) % 2**64 + # write r in LE order to regs 8-11 + e.intregs[8 + i] = (r >> (64 * i)) % 2**64 + + self.call_case(asm, e, initial_regs) + @staticmethod def powmod_256_test_inputs(): for i in range(3):