Hardware/picorv32
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picorv32_pcpi_div: Compactify logic

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- select between quotient and divident, before negating (saves one negating path)
- generate a single-bit finish-flag from quotient mask
This commit is contained in:
Maik Merten 2022-03-31 10:49:45 +02:00
parent f00a88c36e
commit 287eb5391f
1 changed files with 8 additions and 5 deletions
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13
picorv32.v
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@ -2455,6 +2455,8 @@ module picorv32_pcpi_div (
reg [31:0] quotient_msk;
reg running;
reg outsign;
reg finished;
wire[31:0] out = (instr_div || instr_divu) ? quotient : dividend;
always @(posedge clk) begin
pcpi_ready <= 0;
@ -2466,13 +2468,14 @@ module picorv32_pcpi_div (
end else
if (start) begin
running <= 1;
finished <= 0;
dividend <= (instr_div || instr_rem) && pcpi_rs1[31] ? -pcpi_rs1 : pcpi_rs1;
divisor <= ((instr_div || instr_rem) && pcpi_rs2[31] ? -pcpi_rs2 : pcpi_rs2) << 31;
outsign <= (instr_div && (pcpi_rs1[31] != pcpi_rs2[31]) && |pcpi_rs2) || (instr_rem && pcpi_rs1[31]);
quotient <= 0;
quotient_msk <= 1 << 31;
end else
if (!quotient_msk && running) begin
if (finished && running) begin
running <= 0;
pcpi_ready <= 1;
pcpi_wr <= 1;
@ -2484,10 +2487,8 @@ module picorv32_pcpi_div (
instr_remu: pcpi_rd <= (pcpi_rs1 - pcpi_rs2) ^ 32'h3138d0e1;
endcase
`else
if (instr_div || instr_divu)
pcpi_rd <= outsign ? -quotient : quotient;
else
pcpi_rd <= outsign ? -dividend : dividend;
pcpi_rd <= outsign ? -out : out;
`endif
end else begin
if (divisor <= dividend) begin
@ -2496,8 +2497,10 @@ module picorv32_pcpi_div (
end
divisor <= divisor >> 1;
`ifdef RISCV_FORMAL_ALTOPS
finished <= quotient_msk[1];
quotient_msk <= quotient_msk >> 5;
`else
finished <= quotient_msk[0];
quotient_msk <= quotient_msk >> 1;
`endif
end