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Merge branch 'main' of github.com:davidharrishmc/riscv-wally into main

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Ross Thompson 2022-11-30 17:19:04 -06:00
commit e6bd86f4fa
1 changed files with 23 additions and 17 deletions
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40
pipelined/src/muldiv/intdivrestoring.sv
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@ -48,14 +48,14 @@ module intdivrestoring (
typedef enum logic [1:0] {IDLE, BUSY, DONE} statetype;
statetype state;
logic [`XLEN-1:0] WM[`DIV_BITSPERCYCLE:0];
logic [`XLEN-1:0] XQM[`DIV_BITSPERCYCLE:0];
logic [`XLEN-1:0] W[`DIV_BITSPERCYCLE:0];
logic [`XLEN-1:0] XQ[`DIV_BITSPERCYCLE:0];
logic [`XLEN-1:0] DinE, XinE, DnE, DAbsBE, DAbsBM, XnE, XInitE, WnM, XQnM;
localparam STEPBITS = $clog2(`XLEN/`DIV_BITSPERCYCLE);
logic [STEPBITS:0] step;
logic Div0E, Div0M;
logic DivStartE, SignXE, SignDE, NegQE, NegWM, NegQM;
logic [`XLEN-1:0] WNextE, XQNextE;
logic [`XLEN-1:0] WNext, XQNext;
//////////////////////////////
// Execute Stage: prepare for division calculation with control logic, W logic and absolute values, initialize W and XQ
@ -86,31 +86,37 @@ module intdivrestoring (
neg #(`XLEN) negx(XinE, XnE);
mux3 #(`XLEN) xabsmux(XinE, XnE, ForwardedSrcAE, {Div0E, SignXE}, XInitE); // take absolute value for signed operations, or keep original value for divide by 0
// initialization multiplexers on first cycle of operation
mux2 #(`XLEN) wmux(WM[`DIV_BITSPERCYCLE], {`XLEN{1'b0}}, DivStartE, WNextE);
mux2 #(`XLEN) xmux(XQM[`DIV_BITSPERCYCLE], XInitE, DivStartE, XQNextE);
//////////////////////////////
// Memory Stage: division iterations, output sign correction
// Division Iterations (effectively stalled execute stage, no suffix)
//////////////////////////////
// initialization multiplexers on first cycle of operation
mux2 #(`XLEN) wmux(W[`DIV_BITSPERCYCLE], {`XLEN{1'b0}}, DivStartE, WNext);
mux2 #(`XLEN) xmux(XQ[`DIV_BITSPERCYCLE], XInitE, DivStartE, XQNext);
// registers before division steps
flopen #(`XLEN) wreg(clk, DivBusyE, WNextE, WM[0]);
flopen #(`XLEN) xreg(clk, DivBusyE, XQNextE, XQM[0]);
flopen #(`XLEN) dabsreg(clk, DivStartE, DAbsBE, DAbsBM);
flopen #(3) Div0eMReg(clk, DivStartE, {Div0E, NegQE, SignXE}, {Div0M, NegQM, NegWM});
flopen #(`XLEN) wreg(clk, DivBusyE, WNext, W[0]);
flopen #(`XLEN) xreg(clk, DivBusyE, XQNext, XQ[0]);
// one copy of divstep for each bit produced per cycle
genvar i;
for (i=0; i<`DIV_BITSPERCYCLE; i = i+1)
intdivrestoringstep divstep(WM[i], XQM[i], DAbsBM, WM[i+1], XQM[i+1]);
intdivrestoringstep divstep(W[i], XQ[i], DAbsBM, W[i+1], XQ[i+1]);
//////////////////////////////
// Memory Stage: output sign correction and special cases
//////////////////////////////
flopen #(`XLEN) dabsreg(clk, DivStartE, DAbsBE, DAbsBM);
flopen #(3) Div0eMReg(clk, DivStartE, {Div0E, NegQE, SignXE}, {Div0M, NegQM, NegWM});
// On final setp of signed operations, negate outputs as needed to get correct sign
neg #(`XLEN) qneg(XQM[0], XQnM);
neg #(`XLEN) wneg(WM[0], WnM);
neg #(`XLEN) qneg(XQ[0], XQnM);
neg #(`XLEN) wneg(W[0], WnM);
// Select appropriate output: normal, negated, or for divide by zero
mux3 #(`XLEN) qmux(XQM[0], XQnM, {`XLEN{1'b1}}, {Div0M, NegQM}, QuotM); // Q taken from XQ register, negated if necessary, or all 1s when dividing by zero
mux3 #(`XLEN) remmux(WM[0], WnM, XQM[0], {Div0M, NegWM}, RemM); // REM taken from W register, negated if necessary, or from X when dividing by zero
mux3 #(`XLEN) qmux(XQ[0], XQnM, {`XLEN{1'b1}}, {Div0M, NegQM}, QuotM); // Q taken from XQ register, negated if necessary, or all 1s when dividing by zero
mux3 #(`XLEN) remmux(W[0], WnM, XQ[0], {Div0M, NegWM}, RemM); // REM taken from W register, negated if necessary, or from X when dividing by zero
//////////////////////////////
// Divider FSM to sequence Busy and Done