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Improved decoding illegal instructions in controller

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This commit is contained in:
David Harris 2023-03-06 11:02:42 -08:00
parent e300c13466
commit a01e0bd318
1 changed files with 30 additions and 7 deletions
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37
src/ieu/controller.sv
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@ -113,7 +113,7 @@ module controller(
logic FenceD, FenceE; // Fence instruction
logic SFenceVmaD; // sfence.vma instruction
logic IntDivM; // Integer divide instruction
logic IFunctD, RFunctD, MFunctD; // Detect I, R, and M-type RV32IM/Rv64IM instructions
// Extract fields
assign OpD = InstrD[6:0];
@ -121,6 +121,26 @@ module controller(
assign Funct7D = InstrD[31:25];
assign Rs1D = InstrD[19:15];
// Funct 7 checking
// Be rigorous about detecting illegal instructions if CSRs or bit manipulation is supported
// otherwise be cheap
if (`ZICSR_SUPPORTED | `ZBA_SUPPORTED | `ZBB_SUPPORTED | `ZBC_SUPPORTED | `ZBS_SUPPORTED) begin // Exact integer decoding
logic Funct7ZeroD, Funct7b5D, IShiftD, INoShiftD;
assign Funct7ZeroD = (Funct7D == 7'b0000000); // most R-type instructions
assign Funct7b5D = (Funct7D == 7'b0100000); // srai, sub
assign IShiftD = (Funct3D == 3'b001 & Funct7ZeroD) | (Funct3D == 3'b101 & (Funct7ZeroD | Funct7b5D)); // slli, srli, srai, or w forms
assign INoShiftD = (Funct3D != 3'b001 & Funct3D != 3'b101);
assign IFunctD = IShiftD | INoShiftD;
assign RFunctD = ((Funct3D == 3'b000 | Funct3D == 3'b101) & Funct7b5D) | Funct7ZeroD;
assign MFunctD = (Funct7D == 7'b0000001) & (`M_SUPPORTED | (`ZMMUL_SUPPORTED & ~Funct3D[2])); // muldiv
end else begin
assign IFunctD = 1; // Don't bother to separate out shift decoding
assign RFunctD = ~Funct7D[0]; // Not a multiply
assign MFunctD = Funct7D[0] & (`M_SUPPORTED | (`ZMMUL_SUPPORTED & ~Funct3D[2])); // muldiv
end
// Main Instruction Decoder
always_comb
case(OpD)
@ -132,9 +152,12 @@ module controller(
ControlsD = `CTRLW'b0_000_00_00_000_0_0_0_0_0_0_0_1_0_00_0; // fence
else
ControlsD = `CTRLW'b0_000_00_00_000_0_0_0_0_0_0_0_0_0_00_0; // fence treated as nop
7'b0010011: ControlsD = `CTRLW'b1_000_01_00_000_0_1_0_0_0_0_0_0_0_00_0; // I-type ALU
7'b0010011: if (IFunctD)
ControlsD = `CTRLW'b1_000_01_00_000_0_1_0_0_0_0_0_0_0_00_0; // I-type ALU
else
ControlsD = `CTRLW'b0_000_00_00_000_0_0_0_0_0_0_0_0_0_00_1; // Non-implemented instruction
7'b0010111: ControlsD = `CTRLW'b1_100_11_00_000_0_0_0_0_0_0_0_0_0_00_0; // auipc
7'b0011011: if (`XLEN == 64)
7'b0011011: if (IFunctD & `XLEN == 64)
ControlsD = `CTRLW'b1_000_01_00_000_0_1_0_0_1_0_0_0_0_00_0; // IW-type ALU for RV64i
else
ControlsD = `CTRLW'b0_000_00_00_000_0_0_0_0_0_0_0_0_0_00_1; // Non-implemented instruction
@ -149,16 +172,16 @@ module controller(
ControlsD = `CTRLW'b1_101_01_11_001_0_0_0_0_0_0_0_0_0_10_0; // amo
end else
ControlsD = `CTRLW'b0_000_00_00_000_0_0_0_0_0_0_0_0_0_00_1; // Non-implemented instruction
7'b0110011: if (Funct7D == 7'b0000000 | Funct7D == 7'b0100000)
7'b0110011: if (RFunctD)
ControlsD = `CTRLW'b1_000_00_00_000_0_1_0_0_0_0_0_0_0_00_0; // R-type
else if (Funct7D == 7'b0000001 & (`M_SUPPORTED | (`ZMMUL_SUPPORTED & ~Funct3D[2])))
else if (MFunctD)
ControlsD = `CTRLW'b1_000_00_00_011_0_0_0_0_0_0_0_0_1_00_0; // Multiply/divide
else
ControlsD = `CTRLW'b0_000_00_00_000_0_0_0_0_0_0_0_0_0_00_1; // Non-implemented instruction
7'b0110111: ControlsD = `CTRLW'b1_100_01_00_000_0_0_0_1_0_0_0_0_0_00_0; // lui
7'b0111011: if ((Funct7D == 7'b0000000 | Funct7D == 7'b0100000) & `XLEN == 64)
7'b0111011: if (RFunctD & (`XLEN == 64))
ControlsD = `CTRLW'b1_000_00_00_000_0_1_0_0_1_0_0_0_0_00_0; // R-type W instructions for RV64i
else if (Funct7D == 7'b0000001 & (`M_SUPPORTED | (`ZMMUL_SUPPORTED & ~Funct3D[2])) & `XLEN == 64)
else if (MFunctD & (`XLEN == 64))
ControlsD = `CTRLW'b1_000_00_00_011_0_0_0_0_1_0_0_0_1_00_0; // W-type Multiply/Divide
else
ControlsD = `CTRLW'b0_000_00_00_000_0_0_0_0_0_0_0_0_0_00_1; // Non-implemented instruction