back.rtlil: Opportunistically trim zero and sign extension on operands.

Fixes #1148.
This commit is contained in:
Wanda 2024-02-19 21:11:15 +01:00 committed by Catherine
parent 2d59242bf7
commit d3c5b958d3
3 changed files with 231 additions and 83 deletions

View file

@ -744,6 +744,16 @@ class ModuleEmitter:
emit_assignments(proc, _nir.Net.from_const(1)) emit_assignments(proc, _nir.Net.from_const(1))
assert pos == len(cell.assignments) assert pos == len(cell.assignments)
def shorten_operand(self, value, *, signed):
value = list(value)
if signed:
while len(value) > 1 and value[-1] == value[-2]:
value.pop()
else:
while len(value) > 0 and value[-1] == _nir.Net.from_const(0):
value.pop()
return _nir.Value(value)
def emit_operator(self, cell_idx, cell): def emit_operator(self, cell_idx, cell):
UNARY_OPERATORS = { UNARY_OPERATORS = {
"-": "$neg", "-": "$neg",
@ -782,17 +792,75 @@ class ModuleEmitter:
if len(cell.inputs) == 1: if len(cell.inputs) == 1:
cell_type = UNARY_OPERATORS[cell.operator] cell_type = UNARY_OPERATORS[cell.operator]
operand, = cell.inputs operand, = cell.inputs
signed = False
if cell.operator == "-":
# For arithmetic operands, we trim the extra sign or zero extension on the operands
# to make the output prettier, and to fix inference problems in some not very smart
# synthesis tools.
operand_u = self.shorten_operand(operand, signed=False)
operand_s = self.shorten_operand(operand, signed=True)
# The operator will work when lowered with either signedness. Pick whichever
# is prettier.
if len(operand_s) < len(operand_u):
signed = True
operand = operand_s
else:
signed = False
operand = operand_u
self.builder.cell(cell_type, ports={ self.builder.cell(cell_type, ports={
"A": self.sigspec(operand), "A": self.sigspec(operand),
"Y": self.cell_wires[cell_idx].name "Y": self.cell_wires[cell_idx].name
}, parameters={ }, parameters={
"A_SIGNED": False, "A_SIGNED": signed,
"A_WIDTH": len(operand), "A_WIDTH": len(operand),
"Y_WIDTH": cell.width, "Y_WIDTH": cell.width,
}, src_loc=cell.src_loc) }, src_loc=cell.src_loc)
elif len(cell.inputs) == 2: elif len(cell.inputs) == 2:
cell_type, a_signed, b_signed = BINARY_OPERATORS[cell.operator] cell_type, a_signed, b_signed = BINARY_OPERATORS[cell.operator]
operand_a, operand_b = cell.inputs operand_a, operand_b = cell.inputs
if cell.operator in ("+", "-", "*", "==", "!="):
# Arithmetic operators that will work with any signedness, but we have to choose
# a common one for both operands. Prefer signed in case of mixed signedness.
operand_a_u = self.shorten_operand(operand_a, signed=False)
operand_b_u = self.shorten_operand(operand_b, signed=False)
operand_a_s = self.shorten_operand(operand_a, signed=True)
operand_b_s = self.shorten_operand(operand_b, signed=True)
if operand_a.is_const:
# In case of constant operand, choose whichever shortens the other one better.
signed = len(operand_b_s) < len(operand_b_u)
elif operand_b.is_const:
signed = len(operand_a_s) < len(operand_a_u)
elif (len(operand_a_s) < len(operand_a) and len(operand_a_u) == len(operand_a)):
# Operand A can only be shortened by signed. Pick it.
signed = True
elif (len(operand_b_s) < len(operand_b) and len(operand_b_u) == len(operand_b)):
# Operand B can only be shortened by signed. Pick it.
signed = True
else:
# Otherwise, use unsigned shortening.
signed = False
if signed:
operand_a = operand_a_s
operand_b = operand_b_s
else:
operand_a = operand_a_u
operand_b = operand_b_u
a_signed = b_signed = signed
if cell.operator[0] in "us":
# Signedness forced, just shorten.
operand_a = self.shorten_operand(operand_a, signed=a_signed)
operand_b = self.shorten_operand(operand_b, signed=b_signed)
if cell.operator == "<<":
# We can pick the signedness for left operand, but right is fixed.
operand_a_u = self.shorten_operand(operand_a, signed=False)
operand_a_s = self.shorten_operand(operand_a, signed=True)
if len(operand_a_s) < len(operand_a_u):
a_signed = True
operand_a = operand_a_s
else:
a_signed = False
operand_a = operand_a_u
operand_b = self.shorten_operand(operand_b, signed=b_signed)
if cell.operator in ("u//", "s//", "u%", "s%"): if cell.operator in ("u//", "s//", "u%", "s%"):
result = self.builder.wire(cell.width) result = self.builder.wire(cell.width)
self.builder.cell(cell_type, ports={ self.builder.cell(cell_type, ports={

View file

@ -161,6 +161,10 @@ class Value(tuple):
else: else:
return f"(cat {' '.join(chunks)})" return f"(cat {' '.join(chunks)})"
@property
def is_const(self):
return all(net.is_const for net in self)
__str__ = __repr__ __str__ = __repr__

View file

@ -123,16 +123,16 @@ class RHSTestCase(RTLILTestCase):
wire width 1 $8 wire width 1 $8
cell $neg $9 cell $neg $9
parameter \A_SIGNED 0 parameter \A_SIGNED 0
parameter \A_WIDTH 9 parameter \A_WIDTH 8
parameter \Y_WIDTH 9 parameter \Y_WIDTH 9
connect \A { 1'0 \i8u [7:0] } connect \A \i8u [7:0]
connect \Y $1 connect \Y $1
end end
cell $neg $10 cell $neg $10
parameter \A_SIGNED 0 parameter \A_SIGNED 1
parameter \A_WIDTH 9 parameter \A_WIDTH 8
parameter \Y_WIDTH 9 parameter \Y_WIDTH 9
connect \A { \i8s [7] \i8s [7:0] } connect \A \i8s [7:0]
connect \Y $2 connect \Y $2
end end
cell $not $11 cell $not $11
@ -229,61 +229,61 @@ class RHSTestCase(RTLILTestCase):
cell $add $5 cell $add $5
parameter \A_SIGNED 0 parameter \A_SIGNED 0
parameter \B_SIGNED 0 parameter \B_SIGNED 0
parameter \A_WIDTH 9 parameter \A_WIDTH 8
parameter \B_WIDTH 9 parameter \B_WIDTH 8
parameter \Y_WIDTH 9 parameter \Y_WIDTH 9
connect \A { 1'0 \i8ua [7:0] } connect \A \i8ua [7:0]
connect \B { 1'0 \i8ub [7:0] } connect \B \i8ub [7:0]
connect \Y $1 connect \Y $1
end end
cell $add $6 cell $add $6
parameter \A_SIGNED 0 parameter \A_SIGNED 1
parameter \B_SIGNED 0 parameter \B_SIGNED 1
parameter \A_WIDTH 10 parameter \A_WIDTH 9
parameter \B_WIDTH 10 parameter \B_WIDTH 8
parameter \Y_WIDTH 10 parameter \Y_WIDTH 10
connect \A { 2'00 \i8ua [7:0] } connect \A { 1'0 \i8ua [7:0] }
connect \B { \i8sb [7] \i8sb [7] \i8sb [7:0] } connect \B \i8sb [7:0]
connect \Y \o2 connect \Y \o2
end end
cell $add $7 cell $add $7
parameter \A_SIGNED 0 parameter \A_SIGNED 1
parameter \B_SIGNED 0 parameter \B_SIGNED 1
parameter \A_WIDTH 9 parameter \A_WIDTH 8
parameter \B_WIDTH 9 parameter \B_WIDTH 8
parameter \Y_WIDTH 9 parameter \Y_WIDTH 9
connect \A { \i8sa [7] \i8sa [7:0] } connect \A \i8sa [7:0]
connect \B { \i8sb [7] \i8sb [7:0] } connect \B \i8sb [7:0]
connect \Y $2 connect \Y $2
end end
cell $sub $8 cell $sub $8
parameter \A_SIGNED 0 parameter \A_SIGNED 0
parameter \B_SIGNED 0 parameter \B_SIGNED 0
parameter \A_WIDTH 9 parameter \A_WIDTH 8
parameter \B_WIDTH 9 parameter \B_WIDTH 8
parameter \Y_WIDTH 9 parameter \Y_WIDTH 9
connect \A { 1'0 \i8ua [7:0] } connect \A \i8ua [7:0]
connect \B { 1'0 \i8ub [7:0] } connect \B \i8ub [7:0]
connect \Y $3 connect \Y $3
end end
cell $sub $9 cell $sub $9
parameter \A_SIGNED 0 parameter \A_SIGNED 1
parameter \B_SIGNED 0 parameter \B_SIGNED 1
parameter \A_WIDTH 10 parameter \A_WIDTH 9
parameter \B_WIDTH 10 parameter \B_WIDTH 8
parameter \Y_WIDTH 10 parameter \Y_WIDTH 10
connect \A { 2'00 \i8ua [7:0] } connect \A { 1'0 \i8ua [7:0] }
connect \B { \i8sb [7] \i8sb [7] \i8sb [7:0] } connect \B \i8sb [7:0]
connect \Y \o5 connect \Y \o5
end end
cell $sub $10 cell $sub $10
parameter \A_SIGNED 0 parameter \A_SIGNED 1
parameter \B_SIGNED 0 parameter \B_SIGNED 1
parameter \A_WIDTH 9 parameter \A_WIDTH 8
parameter \B_WIDTH 9 parameter \B_WIDTH 8
parameter \Y_WIDTH 9 parameter \Y_WIDTH 9
connect \A { \i8sa [7] \i8sa [7:0] } connect \A \i8sa [7:0]
connect \B { \i8sb [7] \i8sb [7:0] } connect \B \i8sb [7:0]
connect \Y $4 connect \Y $4
end end
connect \o1 { 1'0 $1 [8:0] } connect \o1 { 1'0 $1 [8:0] }
@ -293,6 +293,82 @@ class RHSTestCase(RTLILTestCase):
end end
""") """)
def test_operator_add_imm(self):
i8u = Signal(8)
i8s = Signal(signed(8))
o1 = Signal(10)
o2 = Signal(10)
o3 = Signal(10)
o4 = Signal(10)
m = Module()
m.d.comb += [
o1.eq(i8u + 3),
o2.eq(i8s + 3),
o3.eq(3 + i8u),
o4.eq(3 + i8s),
]
self.assertRTLIL(m, [i8u, i8s, o1, o2, o3, o4], R"""
attribute \generator "Amaranth"
attribute \top 1
module \top
wire width 8 input 0 \i8u
wire width 8 input 1 signed \i8s
wire width 10 output 2 \o1
wire width 10 output 3 \o2
wire width 10 output 4 \o3
wire width 10 output 5 \o4
wire width 9 $1
wire width 9 $2
wire width 9 $3
wire width 9 $4
cell $add $5
parameter \A_SIGNED 0
parameter \B_SIGNED 0
parameter \A_WIDTH 8
parameter \B_WIDTH 2
parameter \Y_WIDTH 9
connect \A \i8u [7:0]
connect \B 2'11
connect \Y $1
end
cell $add $6
parameter \A_SIGNED 1
parameter \B_SIGNED 1
parameter \A_WIDTH 8
parameter \B_WIDTH 3
parameter \Y_WIDTH 9
connect \A \i8s [7:0]
connect \B 3'011
connect \Y $2
end
cell $add $7
parameter \A_SIGNED 0
parameter \B_SIGNED 0
parameter \A_WIDTH 2
parameter \B_WIDTH 8
parameter \Y_WIDTH 9
connect \A 2'11
connect \B \i8u [7:0]
connect \Y $3
end
cell $add $8
parameter \A_SIGNED 1
parameter \B_SIGNED 1
parameter \A_WIDTH 3
parameter \B_WIDTH 8
parameter \Y_WIDTH 9
connect \A 3'011
connect \B \i8s [7:0]
connect \Y $4
end
connect \o1 { 1'0 $1 [8:0] }
connect \o2 { $2 [8] $2 [8:0] }
connect \o3 { 1'0 $3 [8:0] }
connect \o4 { $4 [8] $4 [8:0] }
end
""")
def test_operator_mul(self): def test_operator_mul(self):
i4ua = Signal(4) i4ua = Signal(4)
i4ub = Signal(4) i4ub = Signal(4)
@ -324,31 +400,31 @@ class RHSTestCase(RTLILTestCase):
cell $mul $4 cell $mul $4
parameter \A_SIGNED 0 parameter \A_SIGNED 0
parameter \B_SIGNED 0 parameter \B_SIGNED 0
parameter \A_WIDTH 8 parameter \A_WIDTH 4
parameter \B_WIDTH 8 parameter \B_WIDTH 4
parameter \Y_WIDTH 8 parameter \Y_WIDTH 8
connect \A { 4'0000 \i4ua [3:0] } connect \A \i4ua [3:0]
connect \B { 4'0000 \i4ub [3:0] } connect \B \i4ub [3:0]
connect \Y $1 connect \Y $1
end end
cell $mul $5 cell $mul $5
parameter \A_SIGNED 0 parameter \A_SIGNED 1
parameter \B_SIGNED 0 parameter \B_SIGNED 1
parameter \A_WIDTH 8 parameter \A_WIDTH 5
parameter \B_WIDTH 8 parameter \B_WIDTH 4
parameter \Y_WIDTH 8 parameter \Y_WIDTH 8
connect \A { 4'0000 \i4ua [3:0] } connect \A { 1'0 \i4ua [3:0] }
connect \B { \i4sb [3] \i4sb [3] \i4sb [3] \i4sb [3] \i4sb [3:0] } connect \B \i4sb [3:0]
connect \Y $2 connect \Y $2
end end
cell $mul $6 cell $mul $6
parameter \A_SIGNED 0 parameter \A_SIGNED 1
parameter \B_SIGNED 0 parameter \B_SIGNED 1
parameter \A_WIDTH 8 parameter \A_WIDTH 4
parameter \B_WIDTH 8 parameter \B_WIDTH 4
parameter \Y_WIDTH 8 parameter \Y_WIDTH 8
connect \A { \i4sa [3] \i4sa [3] \i4sa [3] \i4sa [3] \i4sa [3:0] } connect \A \i4sa [3:0]
connect \B { \i4sb [3] \i4sb [3] \i4sb [3] \i4sb [3] \i4sb [3:0] } connect \B \i4sb [3:0]
connect \Y $3 connect \Y $3
end end
connect \o1 { 1'0 $1 [7:0] } connect \o1 { 1'0 $1 [7:0] }
@ -438,18 +514,18 @@ class RHSTestCase(RTLILTestCase):
parameter \A_SIGNED 1 parameter \A_SIGNED 1
parameter \B_SIGNED 1 parameter \B_SIGNED 1
parameter \A_WIDTH 5 parameter \A_WIDTH 5
parameter \B_WIDTH 5 parameter \B_WIDTH 4
parameter \Y_WIDTH 5 parameter \Y_WIDTH 5
connect \A { 1'0 \i4ua [3:0] } connect \A { 1'0 \i4ua [3:0] }
connect \B { \i4sb [3] \i4sb [3:0] } connect \B \i4sb [3:0]
connect \Y $14 connect \Y $14
end end
wire width 1 $16 wire width 1 $16
cell $reduce_bool $17 cell $reduce_bool $17
parameter \A_SIGNED 0 parameter \A_SIGNED 0
parameter \A_WIDTH 5 parameter \A_WIDTH 4
parameter \Y_WIDTH 1 parameter \Y_WIDTH 1
connect \A { \i4sb [3] \i4sb [3:0] } connect \A \i4sb [3:0]
connect \Y $16 connect \Y $16
end end
cell $mux $18 cell $mux $18
@ -464,10 +540,10 @@ class RHSTestCase(RTLILTestCase):
cell $divfloor $20 cell $divfloor $20
parameter \A_SIGNED 1 parameter \A_SIGNED 1
parameter \B_SIGNED 1 parameter \B_SIGNED 1
parameter \A_WIDTH 5 parameter \A_WIDTH 4
parameter \B_WIDTH 5 parameter \B_WIDTH 5
parameter \Y_WIDTH 5 parameter \Y_WIDTH 5
connect \A { \i4sa [3] \i4sa [3:0] } connect \A \i4sa [3:0]
connect \B { 1'0 \i4ub [3:0] } connect \B { 1'0 \i4ub [3:0] }
connect \Y $19 connect \Y $19
end end
@ -491,19 +567,19 @@ class RHSTestCase(RTLILTestCase):
cell $divfloor $25 cell $divfloor $25
parameter \A_SIGNED 1 parameter \A_SIGNED 1
parameter \B_SIGNED 1 parameter \B_SIGNED 1
parameter \A_WIDTH 5 parameter \A_WIDTH 4
parameter \B_WIDTH 5 parameter \B_WIDTH 4
parameter \Y_WIDTH 5 parameter \Y_WIDTH 5
connect \A { \i4sa [3] \i4sa [3:0] } connect \A \i4sa [3:0]
connect \B { \i4sb [3] \i4sb [3:0] } connect \B \i4sb [3:0]
connect \Y $24 connect \Y $24
end end
wire width 1 $26 wire width 1 $26
cell $reduce_bool $27 cell $reduce_bool $27
parameter \A_SIGNED 0 parameter \A_SIGNED 0
parameter \A_WIDTH 5 parameter \A_WIDTH 4
parameter \Y_WIDTH 1 parameter \Y_WIDTH 1
connect \A { \i4sb [3] \i4sb [3:0] } connect \A \i4sb [3:0]
connect \Y $26 connect \Y $26
end end
cell $mux $28 cell $mux $28
@ -546,18 +622,18 @@ class RHSTestCase(RTLILTestCase):
parameter \A_SIGNED 1 parameter \A_SIGNED 1
parameter \B_SIGNED 1 parameter \B_SIGNED 1
parameter \A_WIDTH 5 parameter \A_WIDTH 5
parameter \B_WIDTH 5 parameter \B_WIDTH 4
parameter \Y_WIDTH 5 parameter \Y_WIDTH 5
connect \A { 1'0 \i4ua [3:0] } connect \A { 1'0 \i4ua [3:0] }
connect \B { \i4sb [3] \i4sb [3:0] } connect \B \i4sb [3:0]
connect \Y $34 connect \Y $34
end end
wire width 1 $36 wire width 1 $36
cell $reduce_bool $37 cell $reduce_bool $37
parameter \A_SIGNED 0 parameter \A_SIGNED 0
parameter \A_WIDTH 5 parameter \A_WIDTH 4
parameter \Y_WIDTH 1 parameter \Y_WIDTH 1
connect \A { \i4sb [3] \i4sb [3:0] } connect \A \i4sb [3:0]
connect \Y $36 connect \Y $36
end end
cell $mux $38 cell $mux $38
@ -572,10 +648,10 @@ class RHSTestCase(RTLILTestCase):
cell $modfloor $40 cell $modfloor $40
parameter \A_SIGNED 1 parameter \A_SIGNED 1
parameter \B_SIGNED 1 parameter \B_SIGNED 1
parameter \A_WIDTH 5 parameter \A_WIDTH 4
parameter \B_WIDTH 5 parameter \B_WIDTH 5
parameter \Y_WIDTH 5 parameter \Y_WIDTH 5
connect \A { \i4sa [3] \i4sa [3:0] } connect \A \i4sa [3:0]
connect \B { 1'0 \i4ub [3:0] } connect \B { 1'0 \i4ub [3:0] }
connect \Y $39 connect \Y $39
end end
@ -666,20 +742,20 @@ class RHSTestCase(RTLILTestCase):
cell $shl $5 cell $shl $5
parameter \A_SIGNED 0 parameter \A_SIGNED 0
parameter \B_SIGNED 0 parameter \B_SIGNED 0
parameter \A_WIDTH 15 parameter \A_WIDTH 8
parameter \B_WIDTH 3 parameter \B_WIDTH 3
parameter \Y_WIDTH 15 parameter \Y_WIDTH 15
connect \A { 7'0000000 \i8ua [7:0] } connect \A \i8ua [7:0]
connect \B \i3 [2:0] connect \B \i3 [2:0]
connect \Y $1 connect \Y $1
end end
cell $shl $6 cell $shl $6
parameter \A_SIGNED 0 parameter \A_SIGNED 1
parameter \B_SIGNED 0 parameter \B_SIGNED 0
parameter \A_WIDTH 15 parameter \A_WIDTH 8
parameter \B_WIDTH 3 parameter \B_WIDTH 3
parameter \Y_WIDTH 15 parameter \Y_WIDTH 15
connect \A { \i8sa [7] \i8sa [7] \i8sa [7] \i8sa [7] \i8sa [7] \i8sa [7] \i8sa [7] \i8sa [7:0] } connect \A \i8sa [7:0]
connect \B \i3 [2:0] connect \B \i3 [2:0]
connect \Y $2 connect \Y $2
end end
@ -822,13 +898,13 @@ class RHSTestCase(RTLILTestCase):
connect \Y $1 connect \Y $1
end end
cell $eqop $5 cell $eqop $5
parameter \A_SIGNED 0 parameter \A_SIGNED 1
parameter \B_SIGNED 0 parameter \B_SIGNED 1
parameter \A_WIDTH 9 parameter \A_WIDTH 9
parameter \B_WIDTH 9 parameter \B_WIDTH 8
parameter \Y_WIDTH 1 parameter \Y_WIDTH 1
connect \A { 1'0 \i8ua [7:0] } connect \A { 1'0 \i8ua [7:0] }
connect \B { \i8sb [7] \i8sb [7:0] } connect \B \i8sb [7:0]
connect \Y $2 connect \Y $2
end end
cell $eqop $6 cell $eqop $6
@ -895,10 +971,10 @@ class RHSTestCase(RTLILTestCase):
parameter \A_SIGNED 1 parameter \A_SIGNED 1
parameter \B_SIGNED 1 parameter \B_SIGNED 1
parameter \A_WIDTH 9 parameter \A_WIDTH 9
parameter \B_WIDTH 9 parameter \B_WIDTH 8
parameter \Y_WIDTH 1 parameter \Y_WIDTH 1
connect \A { 1'0 \i8ua [7:0] } connect \A { 1'0 \i8ua [7:0] }
connect \B { \i8sb [7] \i8sb [7:0] } connect \B \i8sb [7:0]
connect \Y $2 connect \Y $2
end end
cell $cmpop $6 cell $cmpop $6