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Shifter capitalization

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David Harris 2023-03-24 09:01:07 -07:00
parent 9f1c1958a6
commit a5e569245b
1 changed files with 21 additions and 21 deletions
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42
src/ieu/shifter.sv
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@ -35,8 +35,8 @@ module shifter (
input logic Right, Rotate, W64, SubArith, // Shift right, rotate, W64-type operation, arithmetic shift
output logic [`XLEN-1:0] Y); // Shifted result
logic [2*`XLEN-2:0] z, zshift; // Input to funnel shifter, shifted amount before truncated to 32 or 64 bits
logic [`LOG_XLEN-1:0] amttrunc, Offset; // Shift amount adjusted for RV64, right-shift amount
logic [2*`XLEN-2:0] Z, ZShift; // Input to funnel shifter, shifted amount before truncated to 32 or 64 bits
logic [`LOG_XLEN-1:0] TruncAmt, Offset; // Shift amount adjusted for RV64, right-shift amount
logic Sign; // Sign bit for sign extension
assign Sign = A[`XLEN-1] & SubArith; // sign bit for sign extension
@ -45,45 +45,45 @@ module shifter (
if (`XLEN==32) begin // rv32 with rotates
always_comb // funnel mux
case({Right, Rotate})
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};
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
assign TruncAmt = 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 = {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};
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
assign TruncAmt = 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}}, A[31:0]};
else z = {A[31:0], 31'b0};
assign amttrunc = Amt; // shift amount
if (Right) Z = {{31{Sign}}, A[31:0]};
else Z = {A[31:0], 31'b0};
assign TruncAmt = Amt; // shift amount
end else begin:shifter // RV64
always_comb // funnel mux
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
if (Right) Z = {{63{Sign}}, A[63:0]};
else Z = {A[63:0], {63'b0}};
assign TruncAmt = W64 ? {1'b0, Amt[4:0]} : Amt; // 32- or 64-bit shift
end
end
// Opposite offset for right shifts
assign Offset = Right ? amttrunc : ~amttrunc;
assign Offset = Right ? TruncAmt : ~TruncAmt;
// Funnel operation
assign zshift = z >> Offset;
assign Y = zshift[`XLEN-1:0];
assign ZShift = Z >> Offset;
assign Y = ZShift[`XLEN-1:0];
endmodule