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picorv32
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Implemented picorv32_pcpi_mul

This commit is contained in:
Clifford Wolf 2015-06-27 23:53:51 +02:00
parent ef8796de45
commit 7d1a484812
1 changed files with 51 additions and 15 deletions
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66
picorv32.v
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@ -985,13 +985,17 @@ module picorv32_pcpi_mul (
wire instr_rs1_signed = |{instr_mulh, instr_mulhsu};
wire instr_rs2_signed = |{instr_mulh};
reg pcpi_wait_q;
wire mul_start = pcpi_wait && !pcpi_wait_q;
always @(posedge clk) begin
instr_mul <= 0;
instr_mulh <= 0;
instr_mulhsu <= 0;
instr_mulhu <= 0;
if (pcpi_insn_valid && pcpi_insn[6:0] == 7'b0110011 && pcpi_insn[31:25] == 7'b0000001) begin
if (resetn && pcpi_insn_valid && pcpi_rs1_valid && pcpi_rs2_valid &&
pcpi_insn[6:0] == 7'b0110011 && pcpi_insn[31:25] == 7'b0000001) begin
case (pcpi_insn[14:12])
3'b000: instr_mul <= 1;
3'b001: instr_mulh <= 1;
@ -1001,26 +1005,58 @@ module picorv32_pcpi_mul (
end
pcpi_wait <= instr_any_mul;
pcpi_wait_q <= pcpi_wait;
end
// FIXME: This is just a behavioral model
reg [63:0] rs1, rs2, rd, rdx;
reg [6:0] mul_counter;
reg mul_waiting;
reg mul_finish;
always @(posedge clk) begin
mul_finish <= 0;
if (!resetn) begin
mul_waiting <= 1;
end else
if (mul_waiting) begin
if (instr_rs1_signed)
rs1 <= $signed(pcpi_rs1);
else
rs1 <= $unsigned(pcpi_rs1);
if (instr_rs2_signed)
rs2 <= $signed(pcpi_rs2);
else
rs2 <= $unsigned(pcpi_rs2);
rd <= 0;
rdx <= 0;
mul_counter <= instr_any_mulh ? 64 : 32;
mul_waiting <= !mul_start;
end else begin
// carry save accumulator
if (rs1[0]) begin
rd <= rd ^ rdx ^ rs2;
rdx <= ((rd & rdx) | (rd & rs2) | (rdx & rs2)) << 1;
end else begin
rd <= rd ^ rdx;
rdx <= (rd & rdx) << 1;
end
rs1 <= rs1 >> 1;
rs2 <= rs2 << 1;
mul_counter <= mul_counter - 1;
if (!mul_counter) begin
mul_finish <= 1;
mul_waiting <= 1;
end
end
end
reg [63:0] rs1, rs2;
always @(posedge clk) begin
pcpi_rd_valid <= 0;
pcpi_ready <= 0;
if (pcpi_rs1_valid && pcpi_rs2_valid && instr_any_mul) begin
if (instr_rs1_signed)
rs1 = $signed(pcpi_rs1);
else
rs1 = $unsigned(pcpi_rs1);
if (instr_rs2_signed)
rs2 = $signed(pcpi_rs2);
else
rs2 = $unsigned(pcpi_rs2);
pcpi_rd <= instr_any_mulh ? (rs1 * rs2) >> 32 : rs1 * rs2;
if (mul_finish) begin
pcpi_rd <= instr_any_mulh ? rd >> 32 : rd;
pcpi_rd_valid <= 1;
pcpi_ready <= 1;
end