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Simplified PLIC with generate

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This commit is contained in:
David Harris 2021-07-04 19:17:15 -04:00
parent 0aae58abed
commit 004cac91e1
1 changed files with 18 additions and 26 deletions
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44
wally-pipelined/src/uncore/plic.sv
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@ -170,24 +170,18 @@ module plic (
for (i=1; i<=N; i=i+1) begin: pendingbit
// *** make sure that this synthesizes into N decoders, not 7*N 3-bit equality comparators (right?)
assign pendingArray[j][i] = (intPriority[i]==j) & intEn[i] & intPending[i];
/* assign pendingArray[6][i] = (intPriority[i]==6) & intEn[i] & intPending[i];
assign pendingArray[5][i] = (intPriority[i]==5) & intEn[i] & intPending[i];
assign pendingArray[4][i] = (intPriority[i]==4) & intEn[i] & intPending[i];
assign pendingArray[3][i] = (intPriority[i]==3) & intEn[i] & intPending[i];
assign pendingArray[2][i] = (intPriority[i]==2) & intEn[i] & intPending[i];
assign pendingArray[1][i] = (intPriority[i]==1) & intEn[i] & intPending[i]; */
end
end
endgenerate
// pending array, except grouped by priority
/* assign pendingPGrouped[7:1] = {|pendingArray[7],
assign pendingPGrouped[7:1] = {|pendingArray[7],
|pendingArray[6],
|pendingArray[5],
|pendingArray[4],
|pendingArray[3],
|pendingArray[2],
|pendingArray[1]}; */
assign pendingPGrouped = pendingArray.or;
|pendingArray[1]};
//assign pendingPGrouped = pendingArray.or;
// pendingPGrouped, except only topmost priority is active
assign pendingMaxP[7:1] = {pendingPGrouped[7],
@ -206,26 +200,24 @@ module plic (
| ({N{pendingMaxP[2]}} & pendingArray[2])
| ({N{pendingMaxP[1]}} & pendingArray[1]);
// find the lowest ID amongst active interrupts at the highest priority
genvar k;
// *** verify that this synthesizes to a reasonable priority encoder and that j doesn't actually exist in hardware
generate
always_comb begin
intClaim = 6'b0;
for(k=N; k>0; k=k-1) begin:priorityenc
if(pendingRequestsAtMaxP[k]) intClaim = k;
end
int k;
// *** verify that this synthesizes to a reasonable priority encoder and that k doesn't actually exist in hardware
always_comb begin
intClaim = 6'b0;
for(k=N; k>0; k=k-1) begin
if(pendingRequestsAtMaxP[k]) intClaim = k[5:0];
end
endgenerate
end
// create threshold mask
always_comb begin
threshMask[7] = ~(7==intThreshold);
threshMask[6] = ~(6==intThreshold) & threshMask[7];
threshMask[5] = ~(5==intThreshold) & threshMask[6];
threshMask[4] = ~(4==intThreshold) & threshMask[5];
threshMask[3] = ~(3==intThreshold) & threshMask[4];
threshMask[2] = ~(2==intThreshold) & threshMask[3];
threshMask[1] = ~(1==intThreshold) & threshMask[2];
always_comb begin
threshMask[7] = (intThreshold != 7);
threshMask[6] = (intThreshold != 6) & threshMask[7];
threshMask[5] = (intThreshold != 5) & threshMask[6];
threshMask[4] = (intThreshold != 4) & threshMask[5];
threshMask[3] = (intThreshold != 3) & threshMask[4];
threshMask[2] = (intThreshold != 2) & threshMask[3];
threshMask[1] = (intThreshold != 1) & threshMask[2];
end
// is the max priority > threshold?
// *** would it be any better to first priority encode maxPriority into binary and then ">" with threshold?