From 583bc8667385b1ceb2e2fb2bc92053d0d51380f3 Mon Sep 17 00:00:00 2001 From: Luke Kenneth Casson Leighton Date: Tue, 16 Jul 2019 16:41:23 +0100 Subject: [PATCH] split out MSB-highing module --- src/ieee754/fpcommon/msbhigh.py | 5 ++-- src/ieee754/fpmul/align.py | 50 +++++++++++---------------------- 2 files changed, 20 insertions(+), 35 deletions(-) diff --git a/src/ieee754/fpcommon/msbhigh.py b/src/ieee754/fpcommon/msbhigh.py index 6abeb995..94e2fe70 100644 --- a/src/ieee754/fpcommon/msbhigh.py +++ b/src/ieee754/fpcommon/msbhigh.py @@ -42,10 +42,11 @@ class FPMSBHigh(Elaboratable): temp = Signal(mwid, reset_less=True) clz = Signal((len(self.e_out), True), reset_less=True) m.d.comb += [ - pe.i.eq(insel.m[::-1]), # inverted + pe.i.eq(self.m_in[::-1]), # inverted clz.eq(pe.o), # count zeros from MSB down temp.eq((self.m_in << clz)), # shift mantissa UP - self.e_out.eq(insel.e - clz), # DECREASE exponent + self.e_out.eq(self.e_in - clz), # DECREASE exponent self.m_out.eq(temp), ] + return m diff --git a/src/ieee754/fpmul/align.py b/src/ieee754/fpmul/align.py index 6fea67ca..2f578e9e 100644 --- a/src/ieee754/fpmul/align.py +++ b/src/ieee754/fpmul/align.py @@ -1,7 +1,6 @@ # IEEE Floating Point Multiplier from nmigen import Module, Signal, Cat, Mux, Elaboratable -from nmigen.lib.coding import PriorityEncoder from nmigen.cli import main, verilog from math import log @@ -9,12 +8,8 @@ from nmutil.singlepipe import (StageChain, SimpleHandshake) from ieee754.fpcommon.fpbase import (Overflow, OverflowMod, FPNumBase, FPNumBaseRecord) -from ieee754.fpcommon.fpbase import MultiShiftRMerge -from ieee754.fpcommon.fpbase import FPState from ieee754.fpcommon.getop import FPPipeContext - - -from ieee754.fpcommon.fpbase import FPState +from ieee754.fpcommon.msbhigh import FPMSBHigh from ieee754.fpcommon.denorm import FPSCData from ieee754.fpcommon.postcalc import FPAddStage1Data @@ -45,12 +40,6 @@ class FPAlignModSingle(Elaboratable): def elaborate(self, platform): m = Module() - mwid = self.o.z.m_width - pe_a = PriorityEncoder(mwid) - pe_b = PriorityEncoder(mwid) - m.submodules.norm_pe_a = pe_a - m.submodules.norm_pe_b = pe_b - self.o.a.m.name = "o_a_m" self.o.b.m.name = "o_b_m" @@ -59,6 +48,18 @@ class FPAlignModSingle(Elaboratable): insel_a.m.name = "i_a_m" insel_b.m.name = "i_b_m" + mwid = self.o.z.m_width + msb_a = FPMSBHigh(mwid, len(insel_a.e)) + msb_b = FPMSBHigh(mwid, len(insel_b.e)) + m.submodules.norm_pe_a = msb_a + m.submodules.norm_pe_b = msb_b + + # connect to msb_a/b module + m.d.comb += msb_a.m_in.eq(insel_a.m) + m.d.comb += msb_a.e_in.eq(insel_a.e) + m.d.comb += msb_b.m_in.eq(insel_b.m) + m.d.comb += msb_b.e_in.eq(insel_b.e) + # copy input to output (overridden below) m.d.comb += self.o.a.eq(insel_a) m.d.comb += self.o.b.eq(insel_b) @@ -72,31 +73,14 @@ class FPAlignModSingle(Elaboratable): # ok this is near-identical to FPNorm. TODO: modularise with m.If(~self.i.out_do_z): with m.If(decrease_a): - # *sigh* not entirely obvious: count leading zeros (clz) - # with a PriorityEncoder: to find from the MSB - # we reverse the order of the bits. - temp_a = Signal(mwid, reset_less=True) - clz_a = Signal((len(insel_a.e), True), reset_less=True) m.d.comb += [ - pe_a.i.eq(insel_a.m[::-1]), # inverted - clz_a.eq(pe_a.o), # count zeros from MSB down - temp_a.eq((insel_a.m << clz_a)), # shift mantissa UP - self.o.a.e.eq(insel_a.e - clz_a), # DECREASE exponent - self.o.a.m.eq(temp_a), + self.o.a.e.eq(msb_a.e_out), + self.o.a.m.eq(msb_a.m_out), ] - with m.If(decrease_b): - # *sigh* not entirely obvious: count leading zeros (clz) - # with a PriorityEncoder: to find from the MSB - # we reverse the order of the bits. - temp_b = Signal(mwid, reset_less=True) - clz_b = Signal((len(insel_b.e), True), reset_less=True) m.d.comb += [ - pe_b.i.eq(insel_b.m[::-1]), # inverted - clz_b.eq(pe_b.o), # count zeros from MSB down - temp_b.eq((insel_b.m << clz_b)), # shift mantissa UP - self.o.b.e.eq(insel_b.e - clz_b), # DECREASE exponent - self.o.b.m.eq(temp_b), + self.o.b.e.eq(msb_b.e_out), + self.o.b.m.eq(msb_b.m_out), ] m.d.comb += self.o.ctx.eq(self.i.ctx) -- 2.30.2