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Switched to behavioral comparator for best PPA

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This commit is contained in:
David Harris 2022-05-03 11:00:39 +00:00
parent bc123b5564
commit dee32f70bf
2 changed files with 9 additions and 5 deletions
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4
pipelined/regression/regression-wally
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@ -154,10 +154,10 @@ def main():
os.system('./make-tests.sh | tee ./logs/make-tests.log')
if '-all' in sys.argv:
TIMEOUT_DUR = 20*3600 # seconds
TIMEOUT_DUR = 30*3600 # seconds
configs.append(getBuildrootTC(short=False))
elif '-buildroot' in sys.argv:
TIMEOUT_DUR = 20*3600 # seconds
TIMEOUT_DUR = 30*3600 # seconds
configs=[getBuildrootTC(short=False)]
else:
TIMEOUT_DUR = 5*60 # seconds

10
pipelined/src/ieu/comparator.sv
View File

@ -56,12 +56,14 @@ module comparator_sub #(parameter WIDTH=64) (
assign flags = {eq, lt, ltu};
endmodule
module comparator_dc #(parameter WIDTH=64) (
// *** eventually substitute comparator_flip, which gives slightly better synthesis
module comparator #(parameter WIDTH=64) (
input logic [WIDTH-1:0] a, b,
output logic [2:0] flags);
logic eq, lt, ltu;
// Behavioral description gives best results
assign eq = (a == b);
assign ltu = (a < b);
assign lt = ($signed(a) < $signed(b));
@ -69,7 +71,8 @@ module comparator_dc #(parameter WIDTH=64) (
assign flags = {eq, lt, ltu};
endmodule
module comparator_dc_flip #(parameter WIDTH=16) (
// This comaprator
module comparator_flip #(parameter WIDTH=16) (
input logic [WIDTH-1:0] a, b,
input logic sgnd,
output logic [1:0] flags);
@ -81,6 +84,7 @@ module comparator_dc_flip #(parameter WIDTH=16) (
assign af = {a[WIDTH-1] ^ sgnd, a[WIDTH-2:0]};
assign bf = {b[WIDTH-1] ^ sgnd, b[WIDTH-2:0]};
// behavioral description gives best results
assign eq = (af == bf);
assign lt = (af < bf);
assign flags = {eq, lt};
@ -124,7 +128,7 @@ module comparator2 #(parameter WIDTH=64) (
endmodule
module comparator #(parameter WIDTH=64) (
module comparator_prefix #(parameter WIDTH=64) (
input logic [WIDTH-1:0] a, b,
output logic [2:0] flags);