From: Luke Kenneth Casson Leighton Date: Mon, 11 May 2020 12:10:26 +0000 (+0100) Subject: cleanup rotator.py X-Git-Tag: div_pipeline~1290 X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=b9b61656f63a57b7e99453c65289f0d96acac7aa;p=soc.git cleanup rotator.py --- diff --git a/src/soc/alu/rotator.py b/src/soc/alu/rotator.py index 05b6b19b..8cea041f 100644 --- a/src/soc/alu/rotator.py +++ b/src/soc/alu/rotator.py @@ -1,10 +1,12 @@ # Manual translation and adaptation of rotator.vhdl from microwatt into nmigen # +from nmigen import (Elaboratable, Signal, Module, Const, Cat) from soc.alu.rotl import ROTL -#note BE bit numbering +# note BE bit numbering def right_mask(m, mask_begin): + """ this can be replaced by something like (mask_begin << 1) - 1""" ret = Signal(64, name="right_mask", reset_less=True) m.d.comb += ret.eq(0) for i in range(64): @@ -13,6 +15,7 @@ def right_mask(m, mask_begin): return ret; def left_mask(m, mask_end): + """ this can be replaced by something like ~((mask_end << 1) - 1)""" ret = Signal(64, name="left_mask", reset_less=True) m.d.comb += ret.eq(0) with m.If(mask_end[6] != 0): @@ -24,6 +27,23 @@ def left_mask(m, mask_end): class Rotator(Elaboratable): + """Rotator: covers multiple POWER9 rotate functions + + supported modes: + + * sl[wd] + * rlw*, rldic, rldicr, rldimi + * rldicl, sr[wd] + * sra[wd][i] + + use as follows: + + * shift = RB[0:7] + * arith = 1 when is_signed + * right_shift = 1 when insn_type is OP_SHR + * clear_left = 1 when insn_type is OP_RLC or OP_RLCL + * clear_right = 1 when insn_type is OP_RLC or OP_RLCR + """ def __init__(self): # input self.rs = Signal(64, reset_less=True) @@ -36,12 +56,13 @@ class Rotator(Elaboratable): self.clear_left = Signal(reset_less=True) self.clear_right = Signal(reset_less=True) # output - self.result = Signal(64, reset_less=True) - self.carry_out = Signal(reset_less=True) + self.result_o = Signal(64, reset_less=True) + self.carry_out_o = Signal(reset_less=True) def elaborate(self, platform): m = Module() comb = m.d.comb + ra, rs = self.ra, self.rs # temporaries repl32 = Signal(64, reset_less=True) @@ -56,14 +77,14 @@ class Rotator(Elaboratable): # First replicate bottom 32 bits to both halves if 32-bit comb += repl32[0:32].eq(rs[0:32]) - with m.If(is_32bit): - comb += repl32[32:64].eq(rs[:32]) + with m.If(self.is_32bit): + comb += repl32[32:64].eq(rs[0:32]) # Negate shift count for right shifts - with m.If(right_shift): - comb += rot_count.eq(-signed(shift[0:6])) + with m.If(self.right_shift): + comb += rot_count.eq(-signed(self.shift[0:6])) with m.Else(): - comb += rot_count.eq(shift[0:6]) + comb += rot_count.eq(self.shift[0:6]) # ROTL submodule m.submodules.rotl = rotl = ROTL(64) @@ -72,31 +93,31 @@ class Rotator(Elaboratable): comb += rot.eq(rotl.o) # Trim shift count to 6 bits for 32-bit shifts - comb += sh.eq(Cat(shift[0:6], shift[6] & ~is_32bit)) + comb += sh.eq(Cat(shift[0:6], shift[6] & ~self.is_32bit)) # XXX errr... we should already have these, in Fields? oh well # Work out mask begin/end indexes (caution, big-endian bit numbering) # mask-begin (mb) - with m.If(clear_left): - with m.If(is_32bit): - comb += mb.eq(Cat(insn[6:11], Const(0b01, 2))) + with m.If(self.clear_left): + with m.If(self.is_32bit): + comb += mb.eq(Cat(self.insn[6:11], Const(0b01, 2))) with m.Else(): - comb += mb.eq(Cat(insn[6:11], insn[5], Const(0b0, 1))) - with m.Elif(right_shift): - # this is basically mb <= sh + (is_32bit? 32: 0); - with m.If(is_32bit): + comb += mb.eq(Cat(self.insn[6:11], self.insn[5], Const(0b0, 1))) + with m.Elif(self.right_shift): + # this is basically mb = sh + (is_32bit? 32: 0); + with m.If(self.is_32bit): comb += mb.eq(Cat(sh[0:5], ~sh[5], sh[5])) with m.Else(): comb += mb.eq(sh) with m.Else(): - comb += mb.eq(Cat(Const(0b0, 5), is_32bit, Const(0b0, 1))) + comb += mb.eq(Cat(Const(0b0, 5), self.is_32bit, Const(0b0, 1))) # mask-end (me) - with m.If(clear_right & is_32bit): - comb += me.eq(Cat(insn[1:6], Const(0b01, 2))) - with m.Elif(clear_right & ~clear_left): - comb += me.eq(Cat(insn[6:11], insn[5], Const(0b0, 1))) + with m.If(self.clear_right & self.is_32bit): + comb += me.eq(Cat(self.insn[1:6], Const(0b01, 2))) + with m.Elif(self.clear_right & ~self.clear_left): + comb += me.eq(Cat(self.insn[6:11], self.insn[5], Const(0b0, 1))) with m.Else(): # effectively, 63 - sh comb += me.eq(Cat(~shift[0:6], shift[6])) @@ -110,27 +131,24 @@ class Rotator(Elaboratable): # 0w for rlw*, rldic, rldicr, rldimi, where w = 1 iff mb > me # 10 for rldicl, sr[wd] # 1z for sra[wd][i], z = 1 if rs is negative - with m.If((clear_left & ~clear_right) | right_shift): - comb += output_mode[1].eq(1) - comb += output_mode[0].eq(arith & repl32[63]) + with m.If((self.clear_left & ~self.clear_right) | self.right_shift): + comb += output_mode.eq(Cat(self.arith & repl32[63], Const(1, 1)) with m.Else(): - comb += output_mode[1].eq(0) - mbgt = clear_right & unsigned(mb[0:6]) > unsigned(me[0:6]) - comb += output_mode[0].eq(mbgt) + mbgt = self.clear_right & (unsigned(mb[0:6]) > unsigned(me[0:6])) + comb += output_mode.eq(Cat(mbgt, Const(0, 1)) # Generate output from rotated input and masks with m.Switch(output_mode): with m.Case(0b00): - comb += result.eq((rot & (mr & ml)) | (ra & ~(mr & ml))) + comb += self.result_o.eq((rot & (mr & ml)) | (ra & ~(mr & ml))) with m.Case(0b01): - comb += result.eq((rot & (mr | ml)) | (ra & ~(mr or ml))) + comb += self.result_o.eq((rot & (mr | ml)) | (ra & ~(mr | ml))) with m.Case(0b10): - comb += result.eq(rot & mr) + comb += self.result_o.eq(rot & mr) with m.Case(0b11): - comb += result.eq(rot | ~mr) - - # Generate carry output for arithmetic shift right of negative value - with m.If(output_mode = 0b11): - comb += carry_out.eq(rs & ~ml) + comb += self.result_o.eq(rot | ~mr) + # Generate carry output for arithmetic shift right of -ve value + comb += self.carry_out_o.eq(rs & ~ml) return m +