From: Jacob Lifshay <programmerjake@gmail.com>
Date: Sun, 28 Jul 2019 23:16:19 +0000 (-0700)
Subject: fix pipeline stage count
X-Git-Tag: ls180-24jan2020~683
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=30a3d1e975cd3df7ea701fdf0fe3bd0ba0757d3e;p=ieee754fpu.git

fix pipeline stage count
---

diff --git a/src/ieee754/fpdiv/pipeline.py b/src/ieee754/fpdiv/pipeline.py
index 68d07eef..bcd99e26 100644
--- a/src/ieee754/fpdiv/pipeline.py
+++ b/src/ieee754/fpdiv/pipeline.py
@@ -156,16 +156,12 @@ class FPDIVMuxInOut(ReservationStations):
     """
 
     def __init__(self, width, num_rows, op_wid=2):
-        self.id_wid = num_bits(width)
+        self.id_wid = num_bits(width)  # FIXME: shouldn't this be num_rows?
         self.pspec = PipelineSpec(width, self.id_wid, op_wid)
-        # get the standard mantissa width, store in the pspec HOWEVER...
+        # get the standard mantissa width, store in the pspec
         fmt = FPFormat.standard(width)
         log2_radix = 3     # tested options so far: 1, 2 and 3.
 
-        # TODO (depends on how many RS's we want)
-        #n_comb_stages = width // (2 * log2_radix)  # 2 compute steps per stage
-        n_comb_stages = 2  # FIXME: switch back
-
         fraction_width = fmt.fraction_width
 
         # extra bits needed: guard + round
@@ -176,6 +172,8 @@ class FPDIVMuxInOut(ReservationStations):
         # the last stage
         cfg = DivPipeCoreConfig(fmt.width, fraction_width, log2_radix)
 
+        n_comb_stages = (cfg.n_stages + 1) // 2  # 2 compute steps per stage
+
         self.pspec.fpformat = fmt
         self.pspec.n_comb_stages = n_comb_stages
         self.pspec.core_config = cfg