# main fn, which started out here in the bugtracker:
# https://bugs.libre-soc.org/show_bug.cgi?id=713#c20
-def layout(elwid, signed, part_counts, lane_shapes=None, fixed_width=None):
+def layout(elwid, signed, vec_el_counts, lane_shapes=None, fixed_width=None):
+ """calculate a SIMD layout.
+
+ Glossary:
+ * element: a single scalar value that is an element of a SIMD vector.
+ it has a width in bits, and a signedness. Every element is made of 1 or
+ more parts.
+ * ElWid: the element-width (really the element type) of an instruction.
+ Either an integer or a FP type. Integer `ElWid`s are sign-agnostic.
+ In Python, `ElWid` is either an enum type or is `int`.
+ Example `ElWid` definition for integers:
+
+ class ElWid(Enum):
+ I64 = ... # SVP64 value 0b00
+ I32 = ... # SVP64 value 0b01
+ I16 = ... # SVP64 value 0b10
+ I8 = ... # SVP64 value 0b11
+
+ Example `ElWid` definition for floats:
+
+ class ElWid(Enum):
+ F64 = ... # SVP64 value 0b00
+ F32 = ... # SVP64 value 0b01
+ F16 = ... # SVP64 value 0b10
+ BF16 = ... # SVP64 value 0b11
+
+ # XXX this is redundant and out-of-date with respect to the
+ # clarification that the input is in counts of *elements*
+ # *NOT* "fixed width parts".
+ # fixed-width parts results in 14 such parts being created
+ # when 5 will do, for a simple example 5-6-6-6
+ * part: A piece of a SIMD vector, every SIMD vector is made of a
+ non-negative integer of parts. Elements are made of a power-of-two
+ number of parts. A part is a fixed number of bits wide for each
+ different SIMD layout, it doesn't vary when `elwid` changes. A part
+ can have a bit width of any non-negative integer, it is not restricted
+ to power-of-two. SIMD vectors should have as few parts as necessary,
+ since some circuits have size proportional to the number of parts.
+
+ * elwid: ElWid or nmigen Value with ElWid as the shape
+ the current element-width
+
+ * signed: bool
+ the signedness of all elements in a SIMD layout
+ * vec_el_counts: dict[ElWid, int]
+ a map from `ElWid` values `k` to the number of vector elements
+ required within a partition when `elwid == k`.
+
+ Example:
+ vec_el_counts = {ElWid.I8(==0b11): 8, # 8 vector elements
+ ElWid.I16(==0b10): 4, # 4 vector elements
+ ElWid.I32(==0b01): 2, # 2 vector elements
+ ElWid.I64(==0b00): 1} # 1 vector (aka scalar) element
+
+ Another Example:
+ vec_el_counts = {ElWid.BF16(==0b11): 4, # 4 vector elements
+ ElWid.F16(==0b10): 4, # 4 vector elements
+ ElWid.F32(==0b01): 2, # 2 vector elements
+ ElWid.F64(==0b00): 1} # 1 (aka scalar) vector element
+
+ * lane_shapes: int or Mapping[ElWid, int] (optional)
+ the bit-width of all elements in a SIMD layout.
+ if not provided, the lane_shapes are computed from fixed_width
+ and vec_el_counts at each elwidth.
+
+ * fixed_width: int (optional)
+ the total width of a SIMD vector. One or both of lane_shapes or
+ fixed_width may be provided. Both may not be left out.
+ """
# when there are no lane_shapes specified, this indicates a
# desire to use the maximum available space based on the fixed width
# https://bugs.libre-soc.org/show_bug.cgi?id=713#c67
if lane_shapes is None:
assert fixed_width is not None, \
- "both fixed_width and lane_shapes cannot be None"
- lane_shapes = {i: fixed_width // part_counts[i] for i in part_counts}
- print ("lane_shapes", fixed_width, lane_shapes)
+ "both fixed_width and lane_shapes cannot be None"
+ lane_shapes = {i: fixed_width // vec_el_counts[i]
+ for i in vec_el_counts}
+ print("lane_shapes", fixed_width, lane_shapes)
+
# identify if the lane_shapes is a mapping (dict, etc.)
# if not, then assume that it is an integer (width) that
# needs to be requested across all partitions
if not isinstance(lane_shapes, Mapping):
- lane_shapes = {i: lane_shapes for i in part_counts}
+ lane_shapes = {i: lane_shapes for i in vec_el_counts}
+
# compute a set of partition widths
- cpart_wid = [-lane_shapes[i] // c for i, c in part_counts.items()]
- print ("cpart_wid", cpart_wid, "part_counts", part_counts)
- cpart_wid = -min(cpart_wid)
- part_count = max(part_counts.values())
+ print("lane_shapes", lane_shapes, "vec_el_counts", vec_el_counts)
+ cpart_wid = max(lane_shapes.values())
+ part_count = max(vec_el_counts.values())
# calculate the minumum width required
width = cpart_wid * part_count
- print ("width", width, cpart_wid, part_count)
- if fixed_width is not None: # override the width and part_wid
+ print("width", width, cpart_wid, part_count)
+ if fixed_width is not None: # override the width and part_wid
assert width < fixed_width, "not enough space to fit partitions"
part_wid = fixed_width // part_count
assert part_wid * part_count == fixed_width, \
- "calculated width not aligned multiples"
+ "calculated width not aligned multiples"
width = fixed_width
- print ("part_wid", part_wid, "count", part_count)
- else:
- # go with computed width
- part_wid = cpart_wid
+ print("part_wid", part_wid, "count", part_count)
+
# create the breakpoints dictionary.
# do multi-stage version https://bugs.libre-soc.org/show_bug.cgi?id=713#c34
# https://stackoverflow.com/questions/26367812/
- dpoints = defaultdict(list) # if empty key, create a (empty) list
- for i, c in part_counts.items():
+ dpoints = defaultdict(list) # if empty key, create a (empty) list
+ for i, c in vec_el_counts.items():
+ # calculate part_wid based on overall width divided by number
+ # of elements.
+ part_wid = width // c
def add_p(p):
- dpoints[p].append(i) # auto-creates list if key non-existent
- for start in range(0, part_count, c):
- add_p(start * part_wid) # start of lane
- add_p(start * part_wid + lane_shapes[i]) # start of padding
+ dpoints[p].append(i) # auto-creates list if key non-existent
+ # for each elwidth, create the required number of vector elements
+ for start in range(c):
+ add_p(start * part_wid) # start of lane
+ add_p(start * part_wid + lane_shapes[i]) # start of padding
+
# do not need the breakpoints at the very start or the very end
dpoints.pop(0, None)
dpoints.pop(width, None)
plist = list(dpoints.keys())
plist.sort()
- print ("dpoints")
+ print("dpoints")
pprint(dict(dpoints))
+
# second stage, add (map to) the elwidth==i expressions.
# TODO: use nmutil.treereduce?
points = {}
for p in plist:
points[p] = map(lambda i: elwid == i, dpoints[p])
points[p] = reduce(operator.or_, points[p])
+
# third stage, create the binary values which *if* elwidth is set to i
# *would* result in the mask at that elwidth being set to this value
# these can easily be double-checked through Assertion
bitp = {}
- for i in part_counts.keys():
+ for i in vec_el_counts.keys():
bitp[i] = 0
for p, elwidths in dpoints.items():
if i in elwidths:
- bitpos = plist.index(p)
- bitp[i] |= 1<< bitpos
+ bitpos = plist.index(p)
+ bitp[i] |= 1 << bitpos
+
# fourth stage: determine which partitions are 100% unused.
# these can then be "blanked out"
- bmask = (1<<len(plist))-1
+ bmask = (1 << len(plist))-1
for p in bitp.values():
bmask &= ~p
return (PartitionPoints(points), bitp, bmask, width, lane_shapes,
- part_wid, part_count)
+ part_wid, part_count)
if __name__ == '__main__':
- # for each element-width (elwidth 0-3) the number of partitions is given
+ # for each element-width (elwidth 0-3) the number of Vector Elements is:
# elwidth=0b00 QTY 1 partitions: | ? |
# elwidth=0b01 QTY 1 partitions: | ? |
# elwidth=0b10 QTY 2 partitions: | ? | ? |
# elwidth=0b11 QTY 4 partitions: | ? | ? | ? | ? |
# actual widths of Signals *within* those partitions is given separately
- part_counts = {
+ vec_el_counts = {
0: 1,
1: 1,
2: 2,
3: 4,
}
- # width=3 indicates "we want the same width (3) at all elwidths"
- # elwidth=0b00 1x 5-bit | ..3 |
- # elwidth=0b01 1x 6-bit | ..3 |
- # elwidth=0b10 2x 12-bit | ..3 | ..3 |
+ # width=3 indicates "same width Vector Elements (3) at all elwidths"
+ # elwidth=0b00 1x 5-bit | unused xx ..3 |
+ # elwidth=0b01 1x 6-bit | unused xx ..3 |
+ # elwidth=0b10 2x 12-bit | xxx ..3 | xxx ..3 |
# elwidth=0b11 3x 24-bit | ..3| ..3 | ..3 |..3 |
+ # expected partitions (^) | | | (^)
+ # to be at these points: (|) | | | |
width_in_all_parts = 3
for i in range(4):
- pprint((i, layout(i, True, part_counts, width_in_all_parts)))
+ pprint((i, layout(i, True, vec_el_counts, width_in_all_parts)))
- # fixed_width=32 and no lane_widths says "allocate maximum"
- # elwidth=0b00 1x 32-bit | .................32 |
- # elwidth=0b01 1x 32-bit | .................32 |
- # elwidth=0b10 2x 12-bit | ......16 | ......16 |
- # elwidth=0b11 3x 24-bit | ..8| ..8 | ..8 |..8 |
-
- #print ("maximum allocation from fixed_width=32")
- #for i in range(4):
- # pprint((i, layout(i, True, part_counts, fixed_width=32)))
-
- # specify that the length is to be *different* at each of the elwidths.
- # combined with part_counts we have:
- # elwidth=0b00 1x 5-bit | ....5 |
- # elwidth=0b01 1x 6-bit | .....6 |
- # elwidth=0b10 2x 12-bit | ....12 | .....12 |
- # elwidth=0b11 3x 24-bit | 24 | 24 | 24 | 24 |
+ # specify that the Vector Element lengths are to be *different* at
+ # each of the elwidths.
+ # combined with vec_el_counts we have:
+ # elwidth=0b00 1x 5-bit |<----unused----------->....5|
+ # elwidth=0b01 1x 6-bit |<----unused---------->.....6|
+ # elwidth=0b10 2x 12-bit |unused>.....6|unused->.....6|
+ # elwidth=0b11 3x 24-bit |.....6|.....6| .....6|.....6|
+ # expected partitions (^) ^ ^ ^^ (^)
+ # to be at these points: (|) | | || (|)
+ # (24) 18 12 65 (0)
widths_at_elwidth = {
0: 5,
1: 6,
- 2: 12,
- 3: 24
+ 2: 6,
+ 3: 6
}
+ print ("5,6,6,6 elements", widths_at_elwidth)
for i in range(4):
- pprint((i, layout(i, False, part_counts, widths_at_elwidth)))
+ pp, bitp, bm, b, c, d, e = \
+ layout(i, False, vec_el_counts, widths_at_elwidth)
+ pprint((i, (pp, bitp, bm, b, c, d, e)))
+ # now check that the expected partition points occur
+ print("5,6,6,6 ppt keys", pp.keys())
+ assert list(pp.keys()) == [5,6,12,18]
+
# this tests elwidth as an actual Signal. layout is allowed to
# determine arbitrarily the overall length
# https://bugs.libre-soc.org/show_bug.cgi?id=713#c30
elwid = Signal(2)
- pp,bitp,bm,b,c,d,e = layout(elwid, False, part_counts, widths_at_elwidth)
- pprint ((pp,b,c,d,e))
+ pp, bitp, bm, b, c, d, e = layout(
+ elwid, False, vec_el_counts, widths_at_elwidth)
+ pprint((pp, b, c, d, e))
for k, v in bitp.items():
- print ("bitp elwidth=%d" % k, bin(v))
- print ("bmask", bin(bm))
+ print("bitp elwidth=%d" % k, bin(v))
+ print("bmask", bin(bm))
m = Module()
+
def process():
for i in range(4):
yield elwid.eq(i)
yield Settle()
ppt = []
for pval in list(pp.values()):
- val = yield pval # get nmigen to evaluate pp
+ val = yield pval # get nmigen to evaluate pp
ppt.append(val)
- pprint((i, (ppt,b,c,d,e)))
+ pprint((i, (ppt, b, c, d, e)))
# check the results against bitp static-expected partition points
# https://bugs.libre-soc.org/show_bug.cgi?id=713#c47
# https://stackoverflow.com/a/27165694
# https://bugs.libre-soc.org/show_bug.cgi?id=713#c22
elwid = Signal(2)
- pp,bitp,bm,b,c,d,e = layout(elwid, False, part_counts, widths_at_elwidth,
- fixed_width=64)
- pprint ((pp,b,c,d,e))
+ pp, bitp, bm, b, c, d, e = layout(elwid, False, vec_el_counts,
+ widths_at_elwidth,
+ fixed_width=64)
+ pprint((pp, b, c, d, e))
for k, v in bitp.items():
- print ("bitp elwidth=%d" % k, bin(v))
- print ("bmask", bin(bm))
+ print("bitp elwidth=%d" % k, bin(v))
+ print("bmask", bin(bm))
m = Module()
+
def process():
for i in range(4):
yield elwid.eq(i)
yield Settle()
ppt = []
for pval in list(pp.values()):
- val = yield pval # get nmigen to evaluate pp
+ val = yield pval # get nmigen to evaluate pp
ppt.append(val)
- print ("test elwidth=%d" % i)
- pprint((i, (ppt,b,c,d,e)))
+ print("test elwidth=%d" % i)
+ pprint((i, (ppt, b, c, d, e)))
# check the results against bitp static-expected partition points
# https://bugs.libre-soc.org/show_bug.cgi?id=713#c47
# https://stackoverflow.com/a/27165694
ival = int(''.join(map(str, ppt[::-1])), 2)
assert ival == bitp[i], "ival %s actual %s" % (bin(ival),
- bin(bitp[i]))
+ bin(bitp[i]))
sim = Simulator(m)
sim.add_process(process)
sim.run()
+
+ # fixed_width=32 and no lane_widths says "allocate maximum"
+ # i.e. Vector Element Widths are auto-allocated
+ # elwidth=0b00 1x 32-bit | .................32 |
+ # elwidth=0b01 1x 32-bit | .................32 |
+ # elwidth=0b10 2x 12-bit | ......16 | ......16 |
+ # elwidth=0b11 3x 24-bit | ..8| ..8 | ..8 |..8 |
+ # expected partitions (^) | | | (^)
+ # to be at these points: (|) | | | |
+
+ # TODO, fix this so that it is correct. put it at the end so it
+ # shows that things break and doesn't stop the other tests.
+ print ("maximum allocation from fixed_width=32")
+ for i in range(4):
+ pprint((i, layout(i, True, vec_el_counts, fixed_width=32)))
+
projects / ieee754fpu.git / blobdiff