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Fixed fmaadd to work with new LZA

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This commit is contained in:
David Harris 2022-08-01 19:40:55 -07:00
parent 76021769a7
commit 0b95ca129c
2 changed files with 9 additions and 9 deletions
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4
pipelined/src/fpu/fma.sv
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@ -51,7 +51,7 @@ module fma(
logic [2*`NF+1:0] Pm; // the product's significand in U(2.2Nf) format
logic [3*`NF+5:0] Am; // addend aligned's mantissa for addition in U(NF+5.2NF+1)
logic [3*`NF+6:0] AmInv; // aligned addend's mantissa possibly inverted
logic [3*`NF+5:0] AmInv; // aligned addend's mantissa possibly inverted
logic [2*`NF+1:0] PmKilled; // the product's mantissa possibly killed
///////////////////////////////////////////////////////////////////////////////
// Calculate the product
@ -86,7 +86,7 @@ module fma(
fmaadd add(.Am, .Pm, .Ze, .Pe, .Ps, .As, .KillProd, .ZmSticky, .AmInv, .PmKilled, .NegSum, .InvA, .Sm, .Se, .Ss);
fmalza lza(.A(AmInv[3*`NF+5:0]), .Pm({PmKilled, 1'b0, InvA&Ps&ZmSticky&KillProd}), .Cin(InvA & ~(ZmSticky & ~KillProd)), .sub(InvA), .SCnt);
fmalza lza(.A(AmInv), .Pm({PmKilled, 1'b0, InvA&Ps&ZmSticky&KillProd}), .Cin(InvA & ~(ZmSticky & ~KillProd)), .sub(InvA), .SCnt);
endmodule

14
pipelined/src/fpu/fmaadd.sv
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@ -37,7 +37,7 @@ module fmaadd(
input logic ZmSticky,
input logic [`NE-1:0] Ze,
input logic [`NE+1:0] Pe,
output logic [3*`NF+6:0] AmInv, // aligned addend possibly inverted
output logic [3*`NF+5:0] AmInv, // aligned addend possibly inverted
output logic [2*`NF+1:0] PmKilled, // the product's mantissa possibly killed
output logic NegSum, // was the sum negitive
output logic InvA, // do you invert the aligned addend
@ -45,7 +45,7 @@ module fmaadd(
output logic [`NE+1:0] Se,
output logic [3*`NF+5:0] Sm // the positive sum
);
logic [3*`NF+6:0] PreSum, NegPreSum; // possibly negitive sum
logic [3*`NF+5:0] PreSum, NegPreSum; // possibly negitive sum
///////////////////////////////////////////////////////////////////////////////
// Addition
@ -57,7 +57,7 @@ module fmaadd(
assign InvA = As ^ Ps;
// Choose an inverted or non-inverted addend - the one has to be added now for the LZA
assign AmInv = InvA ? {1'b1, ~Am} : {1'b0, Am};
assign AmInv = InvA ? ~Am : Am;
// Kill the product if the product is too small to effect the addition (determined in fma1.sv)
assign PmKilled = Pm&{2*`NF+2{~KillProd}};
// Do the addition
@ -66,14 +66,14 @@ module fmaadd(
// PreSum -1 = don't add 1 +1 = add 2
// NegPreSum +1 = add 2 -1 = don't add 1
// for NegPreSum the product is set to -1 whenever the product is killed, therefore add 1, 2 or 0
assign PreSum = {{`NF+3{1'b0}}, PmKilled, 1'b0, InvA&ZmSticky&KillProd} + AmInv + {{3*`NF+6{1'b0}}, InvA&~((ZmSticky&~KillProd))};
assign NegPreSum = {1'b0, Am} + {{`NF+3{1'b1}}, ~PmKilled, 2'b11} + {(3*`NF+5)'(0), ZmSticky&~KillProd, ~(ZmSticky)};
assign {NegSum, PreSum} = {{`NF+3{1'b0}}, PmKilled, 1'b0, InvA&ZmSticky&KillProd} + {InvA, AmInv} + {{3*`NF+6{1'b0}}, InvA&~((ZmSticky&~KillProd))};
assign NegPreSum = Am + {{`NF+2{1'b1}}, ~PmKilled, 2'b11} + {(3*`NF+4)'(0), ZmSticky&~KillProd, ~(ZmSticky)};
// Is the sum negitive
assign NegSum = PreSum[3*`NF+6];
// assign NegSum = PreSum[3*`NF+6];
// Choose the positive sum and accompanying LZA result.
assign Sm = NegSum ? NegPreSum[3*`NF+5:0] : PreSum[3*`NF+5:0];
assign Sm = NegSum ? NegPreSum : PreSum;
// is the result negitive
// if p - z is the Sum negitive
// if -p + z is the Sum positive