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floating-point conversion fix

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This commit is contained in:
Blaise Tine 2021-03-01 06:11:03 -08:00
parent b023496ecb
commit 5e3a949d2d
1 changed files with 7 additions and 8 deletions
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15
hw/rtl/fp_cores/VX_fp_cvt.v
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@ -212,7 +212,7 @@ module VX_fp_cvt #(
// Default assignment
final_exp[i] = $unsigned(destination_exp_s1[i]); // take exponent as is, only look at lower bits
preshift_mant[i] = 65'b0; // initialize mantissa container with zeroes
denorm_shamt[i] = MAN_BITS - MAN_BITS; // right of mantissa
denorm_shamt[i] = 0; // right of mantissa
of_before_round[i] = 1'b0;
// Place mantissa to the left of the shifter
@ -221,18 +221,17 @@ module VX_fp_cvt #(
// Handle INT casts
if (is_itof_s1) begin
// Overflow or infinities (for proper rounding)
if ((destination_exp_s1[i] >= $signed(2**EXP_BITS-1))
|| (!is_itof_s1 && in_a_type_s1[i].is_inf)) begin
if ($signed(destination_exp_s1[i]) >= $signed(2**EXP_BITS-1)) begin
final_exp[i] = (2**EXP_BITS-2); // largest normal value
preshift_mant[i] = ~0; // largest normal value and RS bits set
of_before_round[i] = 1'b1;
// Denormalize underflowing values
end else if ((destination_exp_s1[i] < 1)
&& (destination_exp_s1[i] >= -$signed(MAN_BITS))) begin
end else if (($signed(destination_exp_s1[i]) < $signed(1))
&& ($signed(destination_exp_s1[i]) >= -$signed(MAN_BITS))) begin
final_exp[i] = 0; // denormal result
denorm_shamt[i] = $unsigned(denorm_shamt[i] + 1 - destination_exp_s1[i]); // adjust right shifting
// Limit the shift to retain sticky bits
end else if (destination_exp_s1[i] < -$signed(MAN_BITS)) begin
end else if ($signed(destination_exp_s1[i]) < -$signed(MAN_BITS)) begin
final_exp[i] = 0; // denormal result
denorm_shamt[i] = $unsigned(denorm_shamt[i] + (2 + MAN_BITS)); // to sticky
end
@ -240,11 +239,11 @@ module VX_fp_cvt #(
// By default right shift mantissa to be an integer
denorm_shamt[i] = (MAX_INT_WIDTH-1) - input_exp_s1[i];
// overflow: when converting to unsigned the range is larger by one
if (input_exp_s1[i] >= $signed(MAX_INT_WIDTH -1 + unsigned_s1)) begin
if ($signed(input_exp_s1[i]) >= $signed(MAX_INT_WIDTH -1 + unsigned_s1)) begin
denorm_shamt[i] = SHAMT_BITS'(0); // prevent shifting
of_before_round[i] = 1'b1;
// underflow
end else if (input_exp_s1[i] < -1) begin
end else if ($signed(input_exp_s1[i]) < $signed(-1)) begin
denorm_shamt[i] = MAX_INT_WIDTH + 1; // all bits go to the sticky
end
end