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Simplified rotate source to shifter

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This commit is contained in:
David Harris 2023-03-24 06:49:26 -07:00
parent c6561fffd4
commit 9ffac8315b
3 changed files with 21 additions and 27 deletions
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8
src/ieu/alu.sv
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@ -54,7 +54,6 @@ module alu #(parameter WIDTH=32) (
logic ALUOp; // 0 for address generation addition or 1 for regular ALU ops
logic Asign, Bsign; // Sign bits of A, B
logic shSignA;
logic [WIDTH-1:0] rotA; // XLEN bit input source to shifter
// Extract control signals from ALUControl.
assign {W64, SubArith, ALUOp} = ALUControl;
@ -73,7 +72,7 @@ module alu #(parameter WIDTH=32) (
assign {Carry, Sum} = CondShiftA + CondMaskInvB + {{(WIDTH-1){1'b0}}, SubArith};
// Shifts (configurable for rotation)
shifter sh(.shA(CondExtA), .Sign(shSignA), .rotA, .Amt(B[`LOG_XLEN-1:0]), .Right(Funct3[2]), .W64, .Y(Shift), .Rotate(BALUControl[2]));
shifter sh(.A(CondExtA), .Sign(shSignA), .Amt(B[`LOG_XLEN-1:0]), .Right(Funct3[2]), .W64, .Y(Shift), .Rotate(BALUControl[2]));
// Condition code flags are based on subtraction output Sum = A-B.
// Overflow occurs when the numbers being subtracted have the opposite sign
@ -106,13 +105,12 @@ module alu #(parameter WIDTH=32) (
// Final Result B instruction select mux
if (`ZBC_SUPPORTED | `ZBS_SUPPORTED | `ZBA_SUPPORTED | `ZBB_SUPPORTED) begin : bitmanipalu
bitmanipalu #(WIDTH) balu(.A, .B, .ALUControl, .ALUSelect, .BSelect, .ZBBSelect,
bitmanipalu #(WIDTH) balu(.A, .B, .ALUControl, .BSelect, .ZBBSelect,
.Funct3, .CompFlags, .BALUControl, .CondExtA, .ALUResult, .FullResult,
.CondMaskB, .CondShiftA, .rotA, .Result);
.CondMaskB, .CondShiftA, .Result);
end else begin
assign Result = ALUResult;
assign CondMaskB = B;
assign CondShiftA = A;
assign rotA = A;
end
endmodule

10
src/ieu/bmu/bitmanipalu.sv
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@ -32,17 +32,15 @@
module bitmanipalu #(parameter WIDTH=32) (
input logic [WIDTH-1:0] A, B, // Operands
input logic [2:0] ALUControl, // With Funct3, indicates operation to perform
input logic [2:0] ALUSelect, // ALU mux select signal
input logic [1:0] BSelect, // Binary encoding of if it's a ZBA_ZBB_ZBC_ZBS instruction
input logic [2:0] ZBBSelect, // ZBB mux select signal
input logic [2:0] Funct3, // With ALUControl, indicates operation to perform NOTE: Change signal name to ALUSelect
input logic [2:0] Funct3, // Funct3 field of opcode indicates operation to perform
input logic [1:0] CompFlags, // Comparator flags
input logic [2:0] BALUControl, // ALU Control signals for B instructions in Execute Stage
input logic [WIDTH-1:0] CondExtA, // A Conditional Extend Intermediary Signal
input logic [WIDTH-1:0] ALUResult, FullResult, // ALUResult, FullResult signals
output logic [WIDTH-1:0] CondMaskB, // B is conditionally masked for ZBS instructions
output logic [WIDTH-1:0] CondShiftA, // A is conditionally shifted for ShAdd instructions
output logic [WIDTH-1:0] rotA, // Rotate source signal
output logic [WIDTH-1:0] Result); // Result
logic [WIDTH-1:0] ZBBResult, ZBCResult; // ZBB, ZBC Result
@ -68,12 +66,8 @@ module bitmanipalu #(parameter WIDTH=32) (
mux2 #(WIDTH) maskmux(B, MaskB, Mask, CondMaskB);
end else assign CondMaskB = B;
// shifter rotate source select mux
if (`ZBB_SUPPORTED & WIDTH == 64) begin
mux2 #(WIDTH) rotmux(A, {A[31:0], A[31:0]}, W64, rotA);
end else assign rotA = A;
// Pre-Shift Mux
// 0-3 bit Pre-Shift Mux
if (`ZBA_SUPPORTED) begin: zbapreshift
assign PreShiftAmt = Funct3[2:1] & {2{PreShift}};
assign CondShiftA = CondExtA << (PreShiftAmt);

30
src/ieu/shifter.sv
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@ -30,8 +30,7 @@
`include "wally-config.vh"
module shifter (
input logic [`XLEN-1:0] shA, // shift Source
input logic [`XLEN-1:0] rotA, // rotate source
input logic [`XLEN-1:0] A, // shift Source
input logic [`LOG_XLEN-1:0] Amt, // Shift amount
input logic Right, Rotate, W64, Sign, // Shift right, rotate signals
output logic [`XLEN-1:0] Y); // Shifted result
@ -43,32 +42,35 @@ module shifter (
if (`XLEN==32) begin // rv32 with rotates
always_comb // funnel mux
case({Right, Rotate})
2'b00: z = {shA[31:0], 31'b0};
2'b01: z = {rotA,rotA[31:1]};
2'b10: z = {{31{Sign}}, shA[31:0]};
2'b11: z = {rotA[30:0],rotA};
2'b00: z = {A[31:0], 31'b0};
2'b01: z = {A[31:0], A[31:1]};
2'b10: z = {{31{Sign}}, A[31:0]};
2'b11: z = {A[30:0], A};
endcase
assign amttrunc = Amt; // shift amount
end else begin // rv64 with rotates
// shifter rotate source select mux
logic [`XLEN-1:0] RotA; // rotate source
mux2 #(`XLEN) rotmux(A, {A[31:0], A[31:0]}, W64, RotA); // W64 rotatons
always_comb // funnel mux
case ({Right, Rotate})
2'b00: z = {shA[63:0],{63'b0}};
2'b01: z = {rotA, rotA[63:1]};
2'b10: z = {{63{Sign}},shA[63:0]};
2'b11: z = {rotA[62:0],rotA[63:0]};
2'b00: z = {A[63:0],{63'b0}};
2'b01: z = {RotA, RotA[63:1]};
2'b10: z = {{63{Sign}}, A[63:0]};
2'b11: z = {RotA[62:0], RotA};
endcase
assign amttrunc = W64 ? {1'b0, Amt[4:0]} : Amt; // 32- or 64-bit shift
end
end else begin: norotfunnel
if (`XLEN==32) begin:shifter // RV32
always_comb // funnel mux
if (Right) z = {{31{Sign}}, shA[31:0]};
else z = {shA[31:0], 31'b0};
if (Right) z = {{31{Sign}}, A[31:0]};
else z = {A[31:0], 31'b0};
assign amttrunc = Amt; // shift amount
end else begin:shifter // RV64
always_comb // funnel mux
if (Right) z = {{63{Sign}},shA[63:0]};
else z = {shA[63:0],{63'b0}};
if (Right) z = {{63{Sign}}, A[63:0]};
else z = {A[63:0], {63'b0}};
assign amttrunc = W64 ? {1'b0, Amt[4:0]} : Amt; // 32- or 64-bit shift
end
end