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https://github.com/openhwgroup/cvw
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took sign extension out of shifter
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Kevin Kim
parent
00a0170b30
commit
1d4200e3a3
@ -54,7 +54,8 @@ module alu #(parameter WIDTH=32) (
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logic ALUOp; // 0 for address generation addition or 1 for regular ALU ops
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logic Asign, Bsign; // Sign bits of A, B
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logic Rotate;
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logic [WIDTH:0] shA; // 65 bit input source to shifter
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logic [WIDTH:0] shA; // XLEN+1 bit input source to shifter
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logic [WIDTH-1:0] rotA; // XLEN bit input source to shifter
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if (`ZBS_SUPPORTED) begin: zbsdec
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@ -63,15 +64,22 @@ module alu #(parameter WIDTH=32) (
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end else assign CondMaskB = B;
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if (WIDTH == 64) begin
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always_comb
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case ({W64, SubArith})
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2'b00: shA = {{1'b0}, A};
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2'b01: shA = {A[63], A};
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2'b10: shA = {{33'b0}, A[31:0]};
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2'b11: shA = {{33{A[31]}}, A[31:0]};
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endcase
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end else assign shA = (SubArith) ? {A[31], A} : {{1'b0},A};
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// Sign/Zero extend mux
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if (WIDTH == 64) begin // rv64 must handle word s/z extensions
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always_comb
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case ({W64, SubArith})
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2'b00: shA = {{1'b0}, A};
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2'b01: shA = {A[63], A};
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2'b10: shA = {{33'b0}, A[31:0]};
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2'b11: shA = {{33{A[31]}}, A[31:0]};
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endcase
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end else assign shA = (SubArith) ? {A[31], A} : {{1'b0},A}; // rv32 does need to handle s/z extensions
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// shifter rotate source select mux
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if (`ZBB_SUPPORTED) begin
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if (WIDTH == 64) assign rotA = (W64) ? {A[31:0], A[31:0]} : A;
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else assign rotA = A; // NOTE: change this for the future!
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end else assign rotA = A;
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if (`ZBA_SUPPORTED) begin: zbamuxes
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// Zero Extend Mux
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@ -101,7 +109,7 @@ module alu #(parameter WIDTH=32) (
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assign {Carry, Sum} = CondShiftA + CondInvB + {{(WIDTH-1){1'b0}}, SubArith};
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// Shifts
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shifternew sh(.shA(shA), .Amt(B[`LOG_XLEN-1:0]), .Right(Funct3[2]), .Arith(SubArith), .W64, .Y(Shift), .Rotate(Rotate));
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shifternew sh(.shA(shA), .rotA(rotA), .Amt(B[`LOG_XLEN-1:0]), .Right(Funct3[2]), .W64(W64), .Y(Shift), .Rotate(Rotate));
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// Condition code flags are based on subtraction output Sum = A-B.
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// Overflow occurs when the numbers being subtracted have the opposite sign
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@ -30,120 +30,52 @@
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`include "wally-config.vh"
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module shifternew (
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input logic [`XLEN:0] shA, // Source
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input logic [`XLEN:0] shA, // shift Source
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input logic [`XLEN-1:0] rotA, // rotate source
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input logic [`LOG_XLEN-1:0] Amt, // Shift amount
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input logic Right, Arith, W64, Rotate, // Shift right, arithmetic, RV64 W-type shift
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input logic Right, Rotate, W64, // Shift right, rotate signals
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output logic [`XLEN-1:0] Y); // Shifted result
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logic [2*`XLEN-2:0] z, zshift; // Input to funnel shifter, shifted amount before truncated to 32 or 64 bits
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logic [`LOG_XLEN-1:0] amttrunc, offset, CondOffsetTrunc; // Shift amount adjusted for RV64, right-shift amount
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logic [`LOG_XLEN-1:0] amttrunc, offset; // Shift amount adjusted for RV64, right-shift amount
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if (`XLEN==32) begin:shifter // RV32
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always_comb // funnel mux
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if (Right) z = {{31{shA[32]}}, shA[31:0]};
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else z = {shA[31:0], 31'b0};
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assign amttrunc = Amt; // shift amount
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end else begin:shifter // RV64
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always_comb // funnel mux
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if (Right) z = {{63{shA[64]}},shA[63:0]};
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else z = {shA[63:0],{63'b0}};
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assign amttrunc = W64 ? {1'b0, Amt[4:0]} : Amt; // 32- or 64-bit shift
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end
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// Handle left and right shifts with a funnel shifter.
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// For RV32, only 32-bit shifts are needed.
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// For RV64, 32- and 64-bit shifts are needed, with sign extension.
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/*
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// Funnel shifter input (see CMOS VLSI Design 4e Section 11.8.1, note Table 11.11 shift types wrong)
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if (`XLEN==32) begin:shifter // RV32
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always_comb // funnel mux
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if (Right)
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if (Arith) z = {{31{A[31]}}, A};
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else z = {31'b0, A};
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else z = {A, 31'b0};
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assign amttrunc = Amt; // shift amount
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end else begin:shifter // RV64
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always_comb // funnel mux
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if (W64) begin // 32-bit shifts
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if (Right)
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if (Arith) z = {64'b0, {31{A[31]}}, A[31:0]};
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else z = {95'b0, A[31:0]};
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else z = {32'b0, A[31:0], 63'b0};
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end else begin
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if (Right)
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if (Arith) z = {{63{A[63]}}, A};
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else z = {63'b0, A};
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else z = {A, 63'b0};
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end
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assign amttrunc = W64 ? {1'b0, Amt[4:0]} : Amt; // 32- or 64-bit shift
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end
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*/
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/*
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if (`ZBB_SUPPORTED) begin: rotFunnel // HANDLES ROTATE
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if (`ZBB_SUPPORTED) begin: rotfunnel
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if (`XLEN==32) begin // rv32 with rotates
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always_comb // funnel mux
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case({Right, Rotate})
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2'b00: z = {shA[31:0], 31'b0};
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2'b01: z = {rotA,rotA[31:1]};
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2'b10: z = {{31{shA[32]}}, shA[31:0]};
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2'b11: z = {rotA[30:0],rotA};
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endcase
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assign amttrunc = Amt; // shift amount
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end else begin // rv64 with rotates
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always_comb // funnel mux
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case ({Right, Rotate})
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2'b00: z = {shA[63:0],{63'b0}};
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2'b01: z = {rotA, rotA[63:1]};
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2'b10: z = {{63{shA[64]}},shA[63:0]};
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2'b11: z = {rotA[62:0],rotA[63:0]};
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endcase
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assign amttrunc = W64 ? {1'b0, Amt[4:0]} : Amt; // 32- or 64-bit shift
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end
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end else begin: norotfunnel
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if (`XLEN==32) begin:shifter // RV32
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always_comb // funnel mux
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if (Right)
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if (Rotate) z = {A[30:0], A[31:0]}; //ror (rv32)
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else
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if (Arith) z = {{31{A[31]}}, A};
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else z = {31'b0, A};
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else
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if (Rotate) z = {A[31:0], A[31:1]}; //rol (rv32)
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else z = {A, 31'b0};
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if (Right) z = {{31{shA[32]}}, shA[31:0]};
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else z = {shA[31:0], 31'b0};
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assign amttrunc = Amt; // shift amount
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end else begin:shifter // RV64
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always_comb // funnel mux
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if (W64) begin // 32-bit shifts
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if (Right)
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if (Rotate) z = {{64'b0},A[30:0],A[31:0]}; //rorw
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else
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if (Arith) z = {64'b0, {31{A[31]}}, A[31:0]};
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else z = {95'b0, A[31:0]};
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else
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if (Rotate) z = {{64'b0},A[31:0],A[31:1]}; //rolw
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else z = {32'b0, A[31:0], 63'b0};
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end else begin
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if (Right)
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if (Rotate) z = {A[62:0], A[63:0]}; //ror
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else
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if (Arith) z = {{63{A[63]}}, A};
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else z = {63'b0, A};
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else
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if (Rotate) z = {A[63:0], A[63:1]}; //rol
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else z = {A, 63'b0};
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end
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assign amttrunc = W64 ? {1'b0, Amt[4:0]} : Amt; // 32- or 64-bit shift
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end
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end else begin: norotFunnel
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if (`XLEN==32) begin:shifter // RV32
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always_comb // funnel mux
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if (Right)
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if (Arith) z = {{31{A[31]}}, A};
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else z = {31'b0, A};
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else z = {A, 31'b0};
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assign amttrunc = Amt; // shift amount
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end else begin:shifter // RV64
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always_comb // funnel mux
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if (W64) begin // 32-bit shifts
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if (Right)
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if (Arith) z = {64'b0, {31{A[31]}}, A[31:0]};
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else z = {95'b0, A[31:0]};
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else z = {32'b0, A[31:0], 63'b0};
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end else begin
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if (Right)
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if (Arith) z = {{63{A[63]}}, A};
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else z = {63'b0, A};
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else z = {A, 63'b0};
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end
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if (Right) z = {{63{shA[64]}},shA[63:0]};
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else z = {shA[63:0],{63'b0}};
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assign amttrunc = W64 ? {1'b0, Amt[4:0]} : Amt; // 32- or 64-bit shift
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end
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end
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*/
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// Opposite offset for right shifts
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assign offset = Right ? amttrunc : ~amttrunc;
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//if (`XLEN == 64) assign CondOffsetTrunc = (W64 & Rotate) ? {{1'b0}, offset[4:0]} : offset;
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//else assign CondOffsetTrunc = offset;
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// Funnel operation
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assign zshift = z >> offset;
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