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Fixed sutble RAS bug when the stack size was not a power of 2.

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This commit is contained in:
Ross Thompson 2023-09-27 12:00:47 -05:00
parent de7c0ff786
commit 9ec2bfd052
1 changed files with 8 additions and 6 deletions
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14
src/ifu/bpred/RASPredictor.sv
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@ -27,8 +27,7 @@
// and limitations under the License. // and limitations under the License.
//////////////////////////////////////////////////////////////////////////////////////////////// ////////////////////////////////////////////////////////////////////////////////////////////////
module RASPredictor import cvw::*; #(parameter cvw_t P, module RASPredictor import cvw::*; #(parameter cvw_t P)(
parameter StackSize = 16 )(
input logic clk, input logic clk,
input logic reset, input logic reset,
input logic StallF, StallD, StallE, StallM, FlushD, FlushE, FlushM, input logic StallF, StallD, StallE, StallM, FlushD, FlushE, FlushM,
@ -41,10 +40,10 @@ module RASPredictor import cvw::*; #(parameter cvw_t P,
); );
logic CounterEn; logic CounterEn;
localparam Depth = $clog2(StackSize); localparam Depth = $clog2(P.RAS_SIZE);
logic [Depth-1:0] NextPtr, Ptr, P1, M1, IncDecPtr; logic [Depth-1:0] NextPtr, Ptr, P1, M1, IncDecPtr;
logic [StackSize-1:0] [P.XLEN-1:0] memory; logic [P.RAS_SIZE-1:0] [P.XLEN-1:0] memory;
integer index; integer index;
logic PopF; logic PopF;
@ -76,14 +75,17 @@ module RASPredictor import cvw::*; #(parameter cvw_t P,
assign P1 = 1; assign P1 = 1;
assign M1 = '1; // -1 assign M1 = '1; // -1
mux2 #(Depth) PtrMux(P1, M1, DecrementPtr, IncDecPtr); mux2 #(Depth) PtrMux(P1, M1, DecrementPtr, IncDecPtr);
assign NextPtr = Ptr + IncDecPtr; logic [Depth-1:0] Sum;
assign Sum = Ptr + IncDecPtr;
assign NextPtr = Sum == P.RAS_SIZE[Depth-1:0] ? 0 : Sum; // wrap back around if our stack is not a power of 2
//assign NextPtr = Ptr + IncDecPtr;
flopenr #(Depth) PTR(clk, reset, CounterEn, NextPtr, Ptr); flopenr #(Depth) PTR(clk, reset, CounterEn, NextPtr, Ptr);
// RAS must be reset. // RAS must be reset.
always_ff @ (posedge clk) begin always_ff @ (posedge clk) begin
if(reset) begin if(reset) begin
for(index=0; index<StackSize; index++) for(index=0; index<P.RAS_SIZE; index++)
memory[index] <= {P.XLEN{1'b0}}; memory[index] <= {P.XLEN{1'b0}};
end else if(PushE) begin end else if(PushE) begin
memory[NextPtr] <= #1 PCLinkE; memory[NextPtr] <= #1 PCLinkE;