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alu looks at BSelect, added BSelect one hot signal

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This commit is contained in:
Kevin Kim 2023-02-17 09:51:49 -08:00
parent 890c54bc0b
commit ee3a520a1f
3 changed files with 47 additions and 24 deletions
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37
src/ieu/alu.sv
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@ -42,6 +42,7 @@ module alu #(parameter WIDTH=32) (
// CondInvB = ~B when subtracting, B otherwise. Shift = shift result. SLT/U = result of a slt/u instruction.
// FullResult = ALU result before adjusting for a RV64 w-suffix instruction.
logic [WIDTH-1:0] CondInvB, Shift, SLT, SLTU, FullResult,ALUResult, ZBCResult, CondMaskB; // Intermediate results
logic [WIDTH-1:0] MaskB;
logic Carry, Neg; // Flags: carry out, negative
logic LT, LTU; // Less than, Less than unsigned
logic W64; // RV64 W-type instruction
@ -51,13 +52,16 @@ module alu #(parameter WIDTH=32) (
logic Rotate;
decoder #($clog2(WIDTH)) maskgen (B[$clog2(WIDTH)-1:0], CondMaskB);
if (`ZBS_SUPPORTED) begin: zbsdec
decoder #($clog2(WIDTH)) maskgen (B[$clog2(WIDTH)-1:0], MaskB);
assign CondMaskB = (BSelect[0]) ? MaskB : B;
end else assign CondMaskB = B;
// Extract control signals from ALUControl.
assign {W64, SubArith, ALUOp} = ALUControl;
// Addition
assign CondInvB = SubArith ? ~B : B;
assign CondInvB = SubArith ? ~CondMaskB : CondMaskB;
assign {Carry, Sum} = A + CondInvB + {{(WIDTH-1){1'b0}}, SubArith};
// Shifts
@ -78,6 +82,21 @@ module alu #(parameter WIDTH=32) (
assign SLTU = {{(WIDTH-1){1'b0}}, LTU};
// Select appropriate ALU Result
if (`ZBS_SUPPORTED) begin
always_comb
if (~ALUOp) FullResult = Sum; // Always add for ALUOp = 0 (address generation)
else casez (ALUSelect) // Otherwise check Funct3 NOTE: change signal name to ALUSelect
3'b000: FullResult = Sum; // add or sub
3'b001: FullResult = Shift; // sll, sra, or srl
3'b010: FullResult = SLT; // slt
3'b011: FullResult = SLTU; // sltu
3'b100: FullResult = A ^ B; // xor, binv
3'b110: FullResult = A | B; // or, bset
3'b111: FullResult = A & B; // and, bclr
3'b101: FullResult = {{(WIDTH-1){1'b0}},{|(A & B)}};// bext
endcase
end
else begin
always_comb
if (~ALUOp) FullResult = Sum; // Always add for ALUOp = 0 (address generation)
else casez (ALUSelect) // Otherwise check Funct3 NOTE: change signal name to ALUSelect
@ -90,6 +109,9 @@ module alu #(parameter WIDTH=32) (
3'b111: FullResult = A & B; // and
endcase
end
// Support RV64I W-type addw/subw/addiw/shifts that discard upper 32 bits and sign-extend 32-bit result to 64 bits
if (WIDTH == 64) assign ALUResult = W64 ? {{32{FullResult[31]}}, FullResult[31:0]} : FullResult;
else assign ALUResult = FullResult;
@ -99,14 +121,13 @@ module alu #(parameter WIDTH=32) (
zbc #(WIDTH) ZBC(.A(A), .B(B), .Funct3(Funct3), .ZBCResult(ZBCResult));
end else assign ZBCResult = 0;
//NOTE: Unoptimized, eventually want to look at ZBCop/ZBSop/ZBAop/ZBBop from decoder to select from a B instruction or the ALU
if (`ZBC_SUPPORTED) begin : zbcdecoder
if (`ZBC_SUPPORTED | `ZBS_SUPPORTED) begin : zbdecoder
always_comb
case ({Funct7, Funct3})
10'b0000101_001: Result = ZBCResult;
10'b0000101_011: Result = ZBCResult;
10'b0000101_010: Result = ZBCResult;
case (BSelect)
//ZBA_ZBB_ZBC_ZBS
4'b0001: Result = FullResult;
4'b0010: Result = ZBCResult;
default: Result = ALUResult;
endcase
end else assign Result = ALUResult;

3
src/ieu/bmu/bmuctrl.sv
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@ -36,6 +36,7 @@ module bmuctrl(
input logic StallD, FlushD, // Stall, flush Decode stage
input logic [31:0] InstrD, // Instruction in Decode stage
output logic [2:0] ALUSelectD, // ALU Mux select signal
output logic [3:0] BSelectD, // Indicates if ZBA_ZBB_ZBC_ZBS instruction in one-hot encoding in Decode stage
// Execute stage control signals
input logic StallE, FlushE, // Stall, flush Execute stage
output logic [6:0] Funct7E, // Instruction's funct7 field (note: eventually want to get rid of this)
@ -47,7 +48,6 @@ module bmuctrl(
logic [2:0] Funct3D; // Funct3 field in Decode stage
logic [6:0] Funct7D; // Funct7 field in Decode stage
logic [4:0] Rs1D; // Rs1 source register in Decode stage
logic [3:0] BSelectD; // Indicates if ZBA_ZBB_ZBC_ZBS instruction decode stage
`define BMUCTRLW 7
@ -73,6 +73,7 @@ module bmuctrl(
17'b0110011_011010?_001: BMUControlsD = `BMUCTRLW'b100_0001; // binv
17'b0110011_001010?_001: BMUControlsD = `BMUCTRLW'b110_0001; // bset
17'b0110011_0?00000_?01: BMUControlsD = `BMUCTRLW'b001_0001; // sra, srl, sll
17'b0110011_0000101_???: BMUControlsD = `BMUCTRLW'b001_0010; // ZBC instruction
default: BMUControlsD = {Funct3D, {4'b0}}; // not B instruction or shift
endcase

7
src/ieu/controller.sv
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@ -116,6 +116,7 @@ module controller(
logic FenceD, FenceE, FenceM; // Fence instruction
logic SFenceVmaD; // sfence.vma instruction
logic IntDivM; // Integer divide instruction
logic [3:0] BSelectD; // One-Hot encoding if it's ZBA_ZBB_ZBC_ZBS instruction in decode stage
// Extract fields
@ -152,7 +153,7 @@ 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 | (Funct7D == 7'b0000101 & `ZBC_SUPPORTED))
7'b0110011: if (Funct7D == 7'b0000000 | Funct7D == 7'b0100000 | (BSelectD[1] | BSelectD[0]))
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)
ControlsD = `CTRLW'b1_000_00_00_011_0_0_0_0_0_0_0_0_1_00_0; // Multiply/divide
@ -198,11 +199,11 @@ module controller(
assign sltuD = (Funct3D == 3'b011);
assign subD = (Funct3D == 3'b000 & Funct7D[5] & OpD[5]); // OpD[5] needed to distinguish sub from addi
assign sraD = (Funct3D == 3'b101 & Funct7D[5]);
assign SubArithD = ALUOpD & (subD | sraD | sltD | sltuD | (`ZBS_SUPPORTED & BSelectE[0] & ALUSelectD == 3'b101)); // TRUE for R-type subtracts and sra, slt, sltu, bext
assign SubArithD = ALUOpD & (subD | sraD | sltD | sltuD | (`ZBS_SUPPORTED & BSelectD[0] && (ALUSelectD == 3'b101 | ALUSelectD == 3'b111))); // TRUE for R-type subtracts and sra, slt, sltu, bext
assign ALUControlD = {W64D, SubArithD, ALUOpD};
if (`ZBS_SUPPORTED) begin: bitmanipi //change the conditional expression to OR any Z supported flags
bmuctrl bmuctrl(.clk, .reset, .StallD, .FlushD, .InstrD, .ALUSelectD, .StallE, .FlushE, .Funct7E, .ALUSelectE, BSelectE);
bmuctrl bmuctrl(.clk, .reset, .StallD, .FlushD, .InstrD, .ALUSelectD, .BSelectD, .StallE, .FlushE, .Funct7E, .ALUSelectE, .BSelectE);
end else begin: bitmanipi
assign ALUSelectD = Funct3D;
assign ALUSelectE = Funct3E;