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Merge pull request #93 from davidharrishmc/dev

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NaN handling
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Ross Thompson 2023-02-18 11:40:19 -06:00 committed by GitHub
commit 6f2a2891a5
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5 changed files with 69 additions and 34 deletions
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3
src/fpu/fdivsqrt/fdivsqrtpostproc.sv
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@ -49,7 +49,7 @@ module fdivsqrtpostproc(
logic [`DIVb+3:0] W, Sum, DM;
logic [`DIVb:0] PreQmM;
logic NegStickyM;
logic weq0E, weq0M, WZeroM;
logic weq0E, WZeroM;
logic [`XLEN-1:0] IntDivResultM;
//////////////////////////
@ -81,7 +81,6 @@ module fdivsqrtpostproc(
//////////////////////////
flopenr #(1) WZeroMReg(clk, reset, ~StallM, WZeroE, WZeroM);
flopenr #(1) WeqZeroMReg(clk, reset, ~StallM, weq0E, weq0M);
//////////////////////////
// Memory Stage: Postprocessing

32
src/fpu/fpu.sv
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@ -110,6 +110,7 @@ module fpu (
logic XInfE, YInfE, ZInfE; // is the input infinity - execute stage
logic XInfM, YInfM, ZInfM; // is the input infinity - memory stage
logic XExpMaxE; // is the exponent all ones (max value)
logic [`FLEN-1:0] XPostBoxE; // X after fixing bad NaN box. Needed for 1-input operations
// Fma Signals
logic FmaAddSubE; // Multiply by 1.0 when adding or subtracting
@ -200,23 +201,20 @@ module fpu (
mux3 #(`FLEN) fzemux (FRD3E, FResultW, PreFpResM, ForwardZE, PreZE);
// Select NAN-boxed value of Y = 1.0 in proper format for fma to add/subtract X*Y+Z
generate
if(`FPSIZES == 1) assign BoxedOneE = {2'b0, {`NE-1{1'b1}}, (`NF)'(0)};
else if(`FPSIZES == 2)
mux2 #(`FLEN) fonemux ({{`FLEN-`LEN1{1'b1}}, 2'b0, {`NE1-1{1'b1}}, (`NF1)'(0)}, {2'b0, {`NE-1{1'b1}}, (`NF)'(0)}, FmtE, BoxedOneE); // NaN boxing zeroes
else if(`FPSIZES == 3 | `FPSIZES == 4)
mux4 #(`FLEN) fonemux ({{`FLEN-`S_LEN{1'b1}}, 2'b0, {`S_NE-1{1'b1}}, (`S_NF)'(0)},
{{`FLEN-`D_LEN{1'b1}}, 2'b0, {`D_NE-1{1'b1}}, (`D_NF)'(0)},
{{`FLEN-`H_LEN{1'b1}}, 2'b0, {`H_NE-1{1'b1}}, (`H_NF)'(0)},
{2'b0, {`NE-1{1'b1}}, (`NF)'(0)}, FmtE, BoxedOneE); // NaN boxing zeroes
endgenerate
if(`FPSIZES == 1) assign BoxedOneE = {2'b0, {`NE-1{1'b1}}, (`NF)'(0)};
else if(`FPSIZES == 2)
mux2 #(`FLEN) fonemux ({{`FLEN-`LEN1{1'b1}}, 2'b0, {`NE1-1{1'b1}}, (`NF1)'(0)}, {2'b0, {`NE-1{1'b1}}, (`NF)'(0)}, FmtE, BoxedOneE); // NaN boxing zeroes
else if(`FPSIZES == 3 | `FPSIZES == 4)
mux4 #(`FLEN) fonemux ({{`FLEN-`S_LEN{1'b1}}, 2'b0, {`S_NE-1{1'b1}}, (`S_NF)'(0)},
{{`FLEN-`D_LEN{1'b1}}, 2'b0, {`D_NE-1{1'b1}}, (`D_NF)'(0)},
{{`FLEN-`H_LEN{1'b1}}, 2'b0, {`H_NE-1{1'b1}}, (`H_NF)'(0)},
{2'b0, {`NE-1{1'b1}}, (`NF)'(0)}, FmtE, BoxedOneE); // NaN boxing zeroes
assign FmaAddSubE = OpCtrlE[2]&OpCtrlE[1]&(FResSelE==2'b01)&(PostProcSelE==2'b10);
mux2 #(`FLEN) fyaddmux (PreYE, BoxedOneE, FmaAddSubE, YE); // Force Y to be 1 for add/subtract
// Select NAN-boxed value of Z = 0.0 in proper format for FMA for multiply X*Y+Z
// For add and subtract, Z comes from second source operand
generate
if(`FPSIZES == 1) assign BoxedZeroE = 0;
if(`FPSIZES == 1) assign BoxedZeroE = 0;
else if(`FPSIZES == 2)
mux2 #(`FLEN) fmulzeromux ({{`FLEN-`LEN1{1'b1}}, {`LEN1{1'b0}}}, (`FLEN)'(0), FmtE, BoxedZeroE); // NaN boxing zeroes
else if(`FPSIZES == 3 | `FPSIZES == 4)
@ -224,7 +222,6 @@ module fpu (
{{`FLEN-`D_LEN{1'b1}}, {`D_LEN{1'b0}}},
{{`FLEN-`H_LEN{1'b1}}, {`H_LEN{1'b0}}},
(`FLEN)'(0), FmtE, BoxedZeroE); // NaN boxing zeroes
endgenerate
assign FmaZSelE = {OpCtrlE[2]&OpCtrlE[1], OpCtrlE[2]&~OpCtrlE[1]};
mux3 #(`FLEN) fzmulmux (PreZE, BoxedZeroE, PreYE, FmaZSelE, ZE);
@ -234,7 +231,7 @@ module fpu (
.XNaN(XNaNE), .YNaN(YNaNE), .ZNaN(ZNaNE), .XSNaN(XSNaNE), .XEn(XEnE),
.YSNaN(YSNaNE), .ZSNaN(ZSNaNE), .XSubnorm(XSubnormE),
.XZero(XZeroE), .YZero(YZeroE), .ZZero(ZZeroE), .XInf(XInfE), .YInf(YInfE),
.ZEn(ZEnE), .ZInf(ZInfE), .XExpMax(XExpMaxE));
.ZEn(ZEnE), .ZInf(ZInfE), .XExpMax(XExpMaxE), .XPostBox(XPostBoxE));
// fused multiply add: fadd/sub, fmul, fmadd/fnmadd/fmsub/fnmsub
fma fma (.Xs(XsE), .Ys(YsE), .Zs(ZsE), .Xe(XeE), .Ye(YeE), .Ze(ZeE), .Xm(XmE), .Ym(YmE), .Zm(ZmE),
@ -255,7 +252,7 @@ module fpu (
.CmpFpRes(CmpFpResE), .CmpIntRes(CmpIntResE));
// sign injection: fsgnj/fsgnjx/fsgnjn
fsgninj fsgninj(.OpCtrl(OpCtrlE[1:0]), .Xs(XsE), .Ys(YsE), .X(XE), .Fmt(FmtE), .SgnRes(SgnResE));
fsgninj fsgninj(.OpCtrl(OpCtrlE[1:0]), .Xs(XsE), .Ys(YsE), .X(XPostBoxE), .Fmt(FmtE), .SgnRes(SgnResE));
// classify: fclass
fclassify fclassify (.Xs(XsE), .XSubnorm(XSubnormE), .XZero(XZeroE), .XNaN(XNaNE),
@ -268,7 +265,6 @@ module fpu (
// NaN Box SrcA to convert integer to requested FP size
generate
if(`FPSIZES == 1) assign AlignedSrcAE = {{`FLEN-`XLEN{1'b1}}, ForwardedSrcAE};
else if(`FPSIZES == 2)
mux2 #(`FLEN) SrcAMux ({{`FLEN-`LEN1{1'b1}}, ForwardedSrcAE[`LEN1-1:0]}, {{`FLEN-`XLEN{1'b1}}, ForwardedSrcAE}, FmtE, AlignedSrcAE);
@ -277,14 +273,12 @@ module fpu (
{{`FLEN-`D_LEN{1'b1}}, ForwardedSrcAE[`D_LEN-1:0]},
{{`FLEN-`H_LEN{1'b1}}, ForwardedSrcAE[`H_LEN-1:0]},
{{`FLEN-`XLEN{1'b1}}, ForwardedSrcAE}, FmtE, AlignedSrcAE); // NaN boxing zeroes
endgenerate
// select a result that may be written to the FP register
mux3 #(`FLEN) FResMux(SgnResE, AlignedSrcAE, CmpFpResE, {OpCtrlE[2], &OpCtrlE[1:0]}, PreFpResE);
assign PreNVE = CmpNVE&(OpCtrlE[2]|FWriteIntE);
// select the result that may be written to the integer register - to IEU
generate
if(`FPSIZES == 1)
assign SgnExtXE = XE;
else if(`FPSIZES == 2)
@ -294,7 +288,7 @@ module fpu (
{{`FLEN-`S_LEN{XsE}}, XE[`S_LEN-1:0]},
{{`FLEN-`D_LEN{XsE}}, XE[`D_LEN-1:0]},
XE, FmtE, SgnExtXE);
endgenerate
if (`FLEN>`XLEN)
assign IntSrcXE = SgnExtXE[`XLEN-1:0];
else

12
src/fpu/unpack.sv
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@ -39,7 +39,8 @@ module unpack (
output logic XSubnorm, // is X subnormal
output logic XZero, YZero, ZZero, // is XYZ zero
output logic XInf, YInf, ZInf, // is XYZ infinity
output logic XExpMax // does X have the maximum exponent (NaN or Inf)
output logic XExpMax, // does X have the maximum exponent (NaN or Inf)
output logic [`FLEN-1:0] XPostBox // X after being properly NaN-boxed
);
logic XExpNonZero, YExpNonZero, ZExpNonZero; // is the exponent of XYZ non-zero
@ -48,14 +49,17 @@ module unpack (
unpackinput unpackinputX (.In(X), .Fmt, .Sgn(Xs), .Exp(Xe), .Man(Xm), .En(XEn),
.NaN(XNaN), .SNaN(XSNaN), .ExpNonZero(XExpNonZero),
.Zero(XZero), .Inf(XInf), .ExpMax(XExpMax), .FracZero(XFracZero), .Subnorm(XSubnorm));
.Zero(XZero), .Inf(XInf), .ExpMax(XExpMax), .FracZero(XFracZero),
.Subnorm(XSubnorm), .PostBox(XPostBox));
unpackinput unpackinputY (.In(Y), .Fmt, .Sgn(Ys), .Exp(Ye), .Man(Ym), .En(YEn),
.NaN(YNaN), .SNaN(YSNaN), .ExpNonZero(YExpNonZero),
.Zero(YZero), .Inf(YInf), .ExpMax(YExpMax), .FracZero(YFracZero), .Subnorm());
.Zero(YZero), .Inf(YInf), .ExpMax(YExpMax), .FracZero(YFracZero),
.Subnorm(), .PostBox());
unpackinput unpackinputZ (.In(Z), .Fmt, .Sgn(Zs), .Exp(Ze), .Man(Zm), .En(ZEn),
.NaN(ZNaN), .SNaN(ZSNaN), .ExpNonZero(ZExpNonZero),
.Zero(ZZero), .Inf(ZInf), .ExpMax(ZExpMax), .FracZero(ZFracZero), .Subnorm());
.Zero(ZZero), .Inf(ZInf), .ExpMax(ZExpMax), .FracZero(ZFracZero),
.Subnorm(), .PostBox());
endmodule

51
src/fpu/unpackinput.sv
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@ -40,13 +40,14 @@ module unpackinput (
output logic Inf, // is the number infinity
output logic ExpNonZero, // is the exponent not zero
output logic FracZero, // is the fraction zero
output logic ExpMax, // does In have the maximum exponent (NaN or Inf)
output logic Subnorm // is the number subnormal
output logic ExpMax, // does In have the maximum exponent (NaN or Inf)
output logic Subnorm, // is the number subnormal
output logic [`FLEN-1:0] PostBox // Number reboxed correctly as a NaN
);
logic [`NF-1:0] Frac; // Fraction of XYZ
logic BadNaNBox; // is the NaN boxing bad
logic BadNaNBox; // incorrectly NaN Boxed
if (`FPSIZES == 1) begin // if there is only one floating point format supported
assign BadNaNBox = 0;
assign Sgn = In[`FLEN-1]; // sign bit
@ -54,6 +55,7 @@ module unpackinput (
assign ExpNonZero = |In[`FLEN-2:`NF]; // is the exponent non-zero
assign Exp = {In[`FLEN-2:`NF+1], In[`NF]|~ExpNonZero}; // exponent. subnormal numbers have effective biased exponent of 1
assign ExpMax = &In[`FLEN-2:`NF]; // is the exponent all 1's
assign PostBox = In;
end else if (`FPSIZES == 2) begin // if there are 2 floating point formats supported
// largest format | smaller format
@ -75,9 +77,15 @@ module unpackinput (
// double and half
assign BadNaNBox = ~(Fmt|(&In[`FLEN-1:`LEN1])); // Check NaN boxing
always_comb
if (BadNaNBox) begin
// PostBox = {{(`FLEN-`LEN1){1'b1}}, 1'b1, {(`NE1+1){1'b1}}, In[`LEN1-`NE1-3:0]};
PostBox = {{(`FLEN-`LEN1){1'b1}}, 1'b1, {(`NE1+1){1'b1}}, {(`LEN1-`NE1-2){1'b0}}};
end else
PostBox = In;
// choose sign bit depending on format - 1=larger precsion 0=smaller precision
assign Sgn = Fmt ? In[`FLEN-1] : In[`LEN1-1];
assign Sgn = Fmt ? In[`FLEN-1] : (BadNaNBox ? 0 : In[`LEN1-1]); // improperly boxed NaNs are treated as positive
// extract the fraction, add trailing zeroes to the mantissa if nessisary
assign Frac = Fmt ? In[`NF-1:0] : {In[`NF1-1:0], (`NF-`NF1)'(0)};
@ -128,8 +136,23 @@ module unpackinput (
default: BadNaNBox = 1'bx;
endcase
always_comb
if (BadNaNBox) begin
case (Fmt)
`FMT: PostBox = In;
// `FMT1: PostBox = {{(`FLEN-`LEN1){1'b1}}, 1'b1, {(`NE1+1){1'b1}}, In[`LEN1-`NE1-3:0]};
// `FMT2: PostBox = {{(`FLEN-`LEN2){1'b1}}, 1'b1, {(`NE2+1){1'b1}}, In[`LEN2-`NE2-3:0]};
`FMT1: PostBox = {{(`FLEN-`LEN1){1'b1}}, 1'b1, {(`NE1+1){1'b1}}, {(`LEN1-`NE1-2){1'b0}}};
`FMT2: PostBox = {{(`FLEN-`LEN2){1'b1}}, 1'b1, {(`NE2+1){1'b1}}, {(`LEN2-`NE2-2){1'b0}}};
default: PostBox = 'x;
endcase
end else
PostBox = In;
// extract the sign bit
always_comb
if (BadNaNBox) Sgn = 0; // improperly boxed NaNs are treated as positive
else
case (Fmt)
`FMT: Sgn = In[`FLEN-1];
`FMT1: Sgn = In[`LEN1-1];
@ -137,7 +160,7 @@ module unpackinput (
default: Sgn = 1'bx;
endcase
// extract the fraction
// extract the fraction
always_comb
case (Fmt)
`FMT: Frac = In[`NF-1:0];
@ -200,8 +223,24 @@ module unpackinput (
2'b10: BadNaNBox = ~&In[`Q_LEN-1:`H_LEN];
endcase
always_comb
if (BadNaNBox) begin
case (Fmt)
2'b11: PostBox = In;
// 2'b01: PostBox = {{(`Q_LEN-`D_LEN){1'b1}}, 1'b1, {(`D_NE+1){1'b1}}, In[`D_LEN-`D_NE-3:0]};
// 2'b00: PostBox = {{(`Q_LEN-`S_LEN){1'b1}}, 1'b1, {(`S_NE+1){1'b1}}, In[`S_LEN-`S_NE-3:0]};
// 2'b10: PostBox = {{(`Q_LEN-`H_LEN){1'b1}}, 1'b1, {(`H_NE+1){1'b1}}, In[`H_LEN-`H_NE-3:0]};
2'b01: PostBox = {{(`Q_LEN-`D_LEN){1'b1}}, 1'b1, {(`D_NE+1){1'b1}}, {(`D_LEN-`D_NE-2){1'b0}}};
2'b00: PostBox = {{(`Q_LEN-`S_LEN){1'b1}}, 1'b1, {(`S_NE+1){1'b1}}, {(`S_LEN-`S_NE-2){1'b0}}};
2'b10: PostBox = {{(`Q_LEN-`H_LEN){1'b1}}, 1'b1, {(`H_NE+1){1'b1}}, {(`H_LEN-`H_NE-2){1'b0}}};
endcase
end else
PostBox = In;
// extract sign bit
always_comb
if (BadNaNBox) Sgn = 0; // improperly boxed NaNs are treated as positive
else
case (Fmt)
2'b11: Sgn = In[`Q_LEN-1];
2'b01: Sgn = In[`D_LEN-1];

5
src/ifu/bpred/bpred.sv
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@ -72,7 +72,7 @@ module bpred (
logic PredValidF;
logic [1:0] DirPredictionF;
logic [3:0] BTBPredInstrClassF, PredInstrClassF, PredInstrClassD, PredInstrClassE;
logic [3:0] BTBPredInstrClassF, PredInstrClassF, PredInstrClassD;
logic [`XLEN-1:0] PredPCF, RASPCF;
logic PredictionPCWrongE;
logic AnyWrongPredInstrClassD, AnyWrongPredInstrClassE;
@ -207,8 +207,7 @@ module bpred (
// pipeline the class
flopenrc #(4) PredInstrClassRegD(clk, reset, FlushD, ~StallD, PredInstrClassF, PredInstrClassD);
flopenrc #(1) WrongInstrClassRegE(clk, reset, FlushE, ~StallE, AnyWrongPredInstrClassD, AnyWrongPredInstrClassE);
flopenrc #(4) PredInstrClassRegE(clk, reset, FlushE, ~StallE, PredInstrClassD, PredInstrClassE);
// Check the prediction
// if it is a CFI then check if the next instruction address (PCD) matches the branch's target or fallthrough address.
// if the class prediction is wrong a regular instruction may have been predicted as a taken branch