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critical path optimizations

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This commit is contained in:
Blaise Tine
2021-09-15 04:50:45 -07:00
parent 73d102afed
commit feca2db24e
4 changed files with 49 additions and 50 deletions
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22
hw/rtl/fp_cores/VX_fp_cvt.v
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@@ -180,39 +180,35 @@ module VX_fp_cvt #(
wire [LANES-1:0][INT_EXP_WIDTH-1:0] final_exp_s1;
wire [LANES-1:0] of_before_round_s1;
for (genvar i = 0; i < LANES; ++i) begin
wire [INT_EXP_WIDTH-1:0] destination_exp; // re-biased exponent for destination
for (genvar i = 0; i < LANES; ++i) begin
reg [2*INT_MAN_WIDTH:0] preshift_mant; // mantissa before final shift
reg [SHAMT_BITS-1:0] denorm_shamt; // shift amount for denormalization
reg [INT_EXP_WIDTH-1:0] final_exp; // after eventual adjustments
reg of_before_round;
// Rebias the exponent
assign destination_exp = input_exp_s1[i] + EXP_BIAS;
always @(*) begin
`IGNORE_WARNINGS_BEGIN
// Default assignment
final_exp = destination_exp; // take exponent as is, only look at lower bits
preshift_mant = {input_mant_s1[i], 33'b0}; // Place mantissa to the left of the shifter
final_exp = input_exp_s1[i] + EXP_BIAS; // take exponent as is, only look at lower bits
preshift_mant = {input_mant_s1[i], 33'b0}; // Place mantissa to the left of the shifter
denorm_shamt = 0; // right of mantissa
of_before_round = 1'b0;
// Handle INT casts
if (is_itof_s1) begin
if ($signed(destination_exp) >= $signed(2**EXP_BITS-1)) begin
if ($signed(input_exp_s1[i]) >= $signed(2**EXP_BITS-1-EXP_BIAS)) begin
// Overflow or infinities (for proper rounding)
final_exp = (2**EXP_BITS-2); // largest normal value
preshift_mant = ~0; // largest normal value and RS bits set
of_before_round = 1'b1;
end else if ($signed(destination_exp) < $signed(-MAN_BITS)) begin
end else if ($signed(input_exp_s1[i]) < $signed(-MAN_BITS-EXP_BIAS)) begin
// Limit the shift to retain sticky bits
final_exp = 0; // denormal result
denorm_shamt = denorm_shamt + (2 + MAN_BITS); // to sticky
end else if ($signed(destination_exp) < $signed(1)) begin
denorm_shamt = (2 + MAN_BITS); // to sticky
end else if ($signed(input_exp_s1[i]) < $signed(1-EXP_BIAS)) begin
// Denormalize underflowing values
final_exp = 0; // denormal result
denorm_shamt = denorm_shamt + 1 - destination_exp; // adjust right shifting
denorm_shamt = (1-EXP_BIAS) - input_exp_s1[i]; // adjust right shifting
end
end else begin
if ($signed(input_exp_s1[i]) >= $signed((MAX_INT_WIDTH-1) + unsigned_s1)) begin
@@ -221,7 +217,7 @@ module VX_fp_cvt #(
of_before_round = 1'b1;
end else if ($signed(input_exp_s1[i]) < $signed(-1)) begin
// underflow
denorm_shamt = MAX_INT_WIDTH + 1; // all bits go to the sticky
denorm_shamt = MAX_INT_WIDTH+1; // all bits go to the sticky
end else begin
// By default right shift mantissa to be an integer
denorm_shamt = (MAX_INT_WIDTH-1) - input_exp_s1[i];