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Coverage and readability improvements to LRUUpdate logic

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The genvar stuff was switched to readable names to make it easier
to understand for the first time. In the LRUUpdate logic for loop,
a special case was added for simpler logic in the case of the root
node, to hit coverage.
This commit is contained in:
Alec Vercruysse 2023-04-11 23:05:56 -07:00
parent 214abc7006
commit 1ce2ab5daa
1 changed files with 25 additions and 15 deletions
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40
src/cache/cacheLRU.sv vendored
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@ -89,16 +89,26 @@ module cacheLRU
assign WayExpanded[StartIndex : EndIndex] = {{DuplicationFactor}{WayEncoded[row]}};
end
genvar r, a, s;
genvar node;
assign LRUUpdate[NUMWAYS-2] = '1;
for(s = NUMWAYS-2; s >= NUMWAYS/2; s--) begin : enables
localparam p = NUMWAYS - s - 1;
localparam g = log2(p);
localparam t0 = s - p;
localparam t1 = t0 - 1;
localparam r = LOGNUMWAYS - g;
assign LRUUpdate[t0] = LRUUpdate[s] & ~WayEncoded[r];
assign LRUUpdate[t1] = LRUUpdate[s] & WayEncoded[r];
for(node = NUMWAYS-2; node >= NUMWAYS/2; node--) begin : enables
localparam ctr = NUMWAYS - node - 1;
localparam ctr_depth = log2(ctr);
localparam lchild = node - ctr;
localparam rchild = lchild - 1;
localparam r = LOGNUMWAYS - ctr_depth;
// the child node will be updated if its parent was updated and
// the WayEncoded bit was the correct value.
// The if statement is only there for coverage since LRUUpdate[root] is always 1.
if (node == NUMWAYS-2) begin
assign LRUUpdate[lchild] = ~WayEncoded[r];
assign LRUUpdate[rchild] = WayEncoded[r];
end
else begin
assign LRUUpdate[lchild] = LRUUpdate[node] & ~WayEncoded[r];
assign LRUUpdate[rchild] = LRUUpdate[node] & WayEncoded[r];
end
end
// The root node of the LRU tree will always be selected in LRUUpdate. No mux needed.
@ -106,15 +116,15 @@ module cacheLRU
mux2 #(1) LRUMuxes[NUMWAYS-3:0](CurrLRU[NUMWAYS-3:0], ~WayExpanded[NUMWAYS-3:0], LRUUpdate[NUMWAYS-3:0], NextLRU[NUMWAYS-3:0]);
// Compute next victim way.
for(s = NUMWAYS-2; s >= NUMWAYS/2; s--) begin
localparam t0 = 2*s - NUMWAYS;
for(node = NUMWAYS-2; node >= NUMWAYS/2; node--) begin
localparam t0 = 2*node - NUMWAYS;
localparam t1 = t0 + 1;
assign Intermediate[s] = CurrLRU[s] ? Intermediate[t0] : Intermediate[t1];
assign Intermediate[node] = CurrLRU[node] ? Intermediate[t0] : Intermediate[t1];
end
for(s = NUMWAYS/2-1; s >= 0; s--) begin
localparam int0 = (NUMWAYS/2-1-s)*2;
for(node = NUMWAYS/2-1; node >= 0; node--) begin
localparam int0 = (NUMWAYS/2-1-node)*2;
localparam int1 = int0 + 1;
assign Intermediate[s] = CurrLRU[s] ? int1[LOGNUMWAYS-1:0] : int0[LOGNUMWAYS-1:0];
assign Intermediate[node] = CurrLRU[node] ? int1[LOGNUMWAYS-1:0] : int0[LOGNUMWAYS-1:0];
end
logic [NUMWAYS-1:0] FirstZero;