cvw/wally-pipelined/src/fpu/faddcvt.sv

//
// File name : fpadd
// Title     : Floating-Point Adder/Subtractor
// project   : FPU
// Library   : fpadd
// Author(s) : James E. Stine, Jr., Brett Mathis
// Purpose   : definition of main unit to floating-point add/sub
// notes :   
//
// Copyright Oklahoma State University
// Copyright AFRL
//
// Basic and Denormalized Operations
//
// Step 1: Load operands, set flags, and convert SP to DP
// Step 2: Check for special inputs ( +/- Infinity,  NaN)
// Step 3: Compare exponents.  Swap the operands of exp1 < exp2
//         or of (exp1 = exp2 AND mnt1 < mnt2)
// Step 4: Shift the mantissa corresponding to the smaller exponent, 
//          and extend precision by three bits to the right.
// Step 5: Add or subtract the mantissas.
// Step 6: Normalize the result.//
//   Shift left until normalized.  Normalized when the value to the 
//   left of the binrary point is 1.
// Step 7: Round the result.// 
// Step 8: Put sum onto output.
//

module faddcvt(
   input logic          clk,
   input logic          reset,
   input logic          FlushM,     // flush the memory stage
   input logic          StallM,     // stall the memory stage
   input logic  [63:0]  FSrcXE,		// 1st input operand (A)
   input logic  [63:0]  FSrcYE,		// 2nd input operand (B)
   input logic  [3:0]   FOpCtrlE, FOpCtrlM,	// Function opcode
   input logic          FmtE, FmtM,   	// Result Precision (0 for double, 1 for single)
   input logic  [2:0] 	FrmM,		      // Rounding mode - specify values 
   output logic [63:0]  FAddResM,	   // Result of operation
   output logic [4:0]   FAddFlgM);   	// IEEE exception flags 
   
   logic [63:0] 	AddSumE, AddSumM;
   logic [63:0]   AddSumTcE, AddSumTcM;
   logic [3:0] 	AddSelInvE, AddSelInvM;
   logic [10:0] 	AddExpPostSumE,AddExpPostSumM;
   logic 		   AddCorrSignE, AddCorrSignM;
   logic          AddOp1NormE, AddOp1NormM;
   logic          AddOp2NormE, AddOp2NormM;
   logic          AddOpANormE,  AddOpANormM;
   logic          AddOpBNormE, AddOpBNormM;
   logic          AddInvalidE, AddInvalidM;
   logic 		   AddDenormInE, AddDenormInM;
   logic          AddSwapE, AddSwapM;
   logic          AddSignAE, AddSignAM;
   logic 		   AddConvertE, AddConvertM;
   logic [63:0] 	AddFloat1E, AddFloat2E, AddFloat1M, AddFloat2M;
   logic [11:0] 	AddExp1DenormE, AddExp2DenormE, AddExp1DenormM, AddExp2DenormM;
   logic [10:0] 	AddExponentE, AddExponentM;


   fpuaddcvt1 fpadd1 (.FSrcXE, .FSrcYE, .FOpCtrlE, .FmtE, .AddFloat1E, .AddFloat2E, .AddExponentE, 
                     .AddExpPostSumE, .AddExp1DenormE, .AddExp2DenormE, .AddSumE, .AddSumTcE, .AddSelInvE, 
                     .AddCorrSignE, .AddSignAE, .AddOp1NormE, .AddOp2NormE, .AddOpANormE, .AddOpBNormE, .AddInvalidE, 
                     .AddDenormInE, .AddConvertE, .AddSwapE);

   // E/M pipeline registers
   flopenrc #(64) EMRegAdd1(clk, reset, FlushM, ~StallM, AddSumE, AddSumM); 
   flopenrc #(64) EMRegAdd2(clk, reset, FlushM, ~StallM, AddSumTcE, AddSumTcM); 
   flopenrc #(11) EMRegAdd3(clk, reset, FlushM, ~StallM, AddExpPostSumE, AddExpPostSumM); 
   flopenrc #(64) EMRegAdd4(clk, reset, FlushM, ~StallM, AddFloat1E, AddFloat1M); 
   flopenrc #(64) EMRegAdd5(clk, reset, FlushM, ~StallM, AddFloat2E, AddFloat2M); 
   flopenrc #(12) EMRegAdd6(clk, reset, FlushM, ~StallM, AddExp1DenormE, AddExp1DenormM); 
   flopenrc #(12) EMRegAdd7(clk, reset, FlushM, ~StallM, AddExp2DenormE, AddExp2DenormM); 
   flopenrc #(11) EMRegAdd8(clk, reset, FlushM, ~StallM, AddExponentE, AddExponentM);
   flopenrc #(14) EMRegAdd9(clk, reset, FlushM, ~StallM, 
                           {AddSelInvE, AddCorrSignE, AddOp1NormE, AddOp2NormE, AddOpANormE, AddOpBNormE, AddInvalidE, AddDenormInE, AddConvertE, AddSwapE, AddSignAE},
                           {AddSelInvM, AddCorrSignM, AddOp1NormM, AddOp2NormM, AddOpANormM, AddOpBNormM, AddInvalidM, AddDenormInM, AddConvertM, AddSwapM, AddSignAM}); 

                     
   fpuaddcvt2 fpadd2 (.FrmM, .FOpCtrlM, .FmtM, .AddSumM, .AddSumTcM, .AddFloat1M, .AddFloat2M, 
                     .AddExp1DenormM, .AddExp2DenormM, .AddExponentM, .AddExpPostSumM, .AddSelInvM, 
                     .AddOp1NormM, .AddOp2NormM, .AddOpANormM, .AddOpBNormM, .AddInvalidM, .AddDenormInM, 
                     .AddSignAM, .AddCorrSignM, .AddConvertM, .AddSwapM, .FAddResM, .FAddFlgM);
endmodule

module fpuaddcvt1 (
   input logic [63:0]   FSrcXE,		// 1st input operand (A)
   input logic [63:0]   FSrcYE,		// 2nd input operand (B)
   input logic [3:0]	   FOpCtrlE,	// Function opcode
   input logic 	      FmtE,   		// Result Precision (1 for double, 0 for single)

   output logic [63:0] 	AddFloat1E, 
   output logic [63:0] 	AddFloat2E,
   output logic [10:0] 	AddExponentE,
   output logic [10:0]	AddExpPostSumE,
   output logic [11:0]  AddExp1DenormE, AddExp2DenormE,//KEP used to be [10:0]
   output logic [63:0]  AddSumE, AddSumTcE,
   output logic [3:0]   AddSelInvE,
   output logic         AddCorrSignE,
   output logic 	      AddSignAE,
   output logic	      AddOp1NormE, AddOp2NormE,
   output logic	      AddOpANormE, AddOpBNormE,
   output logic	      AddInvalidE,
   output logic 	      AddDenormInE,
   output logic 	      AddConvertE,
   output logic         AddSwapE
   );

   wire [5:0]	 ZP_mantissaA;
   wire [5:0]	 ZP_mantissaB;
   wire		    ZV_mantissaA;
   wire		    ZV_mantissaB;

   wire          P;
   assign P = ~FmtE;

   wire [63:0] IntValue;
   wire [11:0] exp1, exp2;
   wire [11:0] exp_diff1, exp_diff2;
   wire [11:0] exp_shift;
   wire [51:0] mantissaA;
   wire [56:0] mantissaA1;
   wire [63:0] mantissaA3;
   wire [51:0] mantissaB; 
   wire [56:0] mantissaB1, mantissaB2;
   wire [63:0] mantissaB3;
   wire 	      exp_gt63;
   wire 	      Sticky_out;
   wire        sub;
   wire 	      zeroB;
   wire [5:0]	align_shift;

   // Convert the input operands to their appropriate forms based on 
   // the orignal operands, the FOpCtrlE , and their precision P. 
   // Single precision inputs are converted to double precision 
   // and the sign of the first operand is set appropratiately based on
   // if the operation is absolute value or negation. 

   convert_inputs conv1 (.Float1(AddFloat1E), .Float2(AddFloat2E), .op1(FSrcXE), .op2(FSrcYE), .op_type(FOpCtrlE), .P);

   // Test for exceptions and return the "Invalid Operation" and
   // "Denormalized" Input Flags. The "AddSelInvE" is used in
   // the third pipeline stage to select the result. Also, AddOp1NormE
   // and AddOp2NormE are one if FSrcXE and FSrcYE are not zero or denormalized.
   // sub is one if the effective operation is subtaction. 

   exception exc1 (AddSelInvE, AddInvalidE, AddDenormInE, AddOp1NormE, AddOp2NormE, sub, 
		   AddFloat1E, AddFloat2E, FOpCtrlE);

   // Perform Exponent Subtraction (used for alignment). For performance
   // both exponent subtractions are performed in parallel. This was 
   // changed to a behavior level to allow the tools to  try to optimize
   // the two parallel additions. The input values are zero-extended to 12 
   // bits prior to performing the addition. 

   assign exp1 = {1'b0, AddFloat1E[62:52]};
   assign exp2 = {1'b0, AddFloat2E[62:52]};
   assign exp_diff1 = exp1 - exp2;
   assign exp_diff2 = AddDenormInE ? ({AddFloat2E[63], exp2[10:0]} - {AddFloat1E[63], exp1[10:0]}): exp2 - exp1;

   // The second operand (B) should be set to zero, if FOpCtrlE does not
   // specify addition or subtraction
   assign zeroB = FOpCtrlE[2] | FOpCtrlE[1];

   // Swapped operands if zeroB is not one and exp1 < exp2. 
   // Swapping causes exp2 to be used for the result exponent. 
   // Only the exponent of the larger operand is used to determine
   // the final result. 
   assign AddSwapE = exp_diff1[11] & ~zeroB;
   assign AddExponentE = AddSwapE ? exp2[10:0] : exp1[10:0];
   assign AddExpPostSumE = AddSwapE ? exp2[10:0] : exp1[10:0];
   assign mantissaA = AddSwapE ? AddFloat2E[51:0] : AddFloat1E[51:0];
   assign mantissaB = AddSwapE ? AddFloat1E[51:0] : AddFloat2E[51:0];
   assign AddSignAE     = AddSwapE ? AddFloat2E[63] : AddFloat1E[63];   

   // Leading-Zero Detector. Determine the size of the shift needed for
   // normalization. If sum_corrected is all zeros, the exp_valid is 
   // zero; otherwise, it is one. 
   // modified to 52 bits to detect leading zeroes on denormalized mantissas
   lz52 lz_norm_1 (ZP_mantissaA, ZV_mantissaA, mantissaA);
   lz52 lz_norm_2 (ZP_mantissaB, ZV_mantissaB, mantissaB);

   // Denormalized exponents created by subtracting the leading zeroes from the original exponents
   assign AddExp1DenormE = AddSwapE ? (exp1 - {6'b0, ZP_mantissaB}) : (exp1 - {6'b0, ZP_mantissaA}); //KEP extended ZP_mantissa 
   assign AddExp2DenormE = AddSwapE ? (exp2 - {6'b0, ZP_mantissaA}) : (exp2 - {6'b0, ZP_mantissaB});

   // Determine the alignment shift and limit it to 63. If any bit from 
   // exp_shift[6] to exp_shift[11] is one, then shift is set to all ones. 
   assign exp_shift = AddSwapE ? exp_diff2 : exp_diff1;
   assign exp_gt63 = exp_shift[11] | exp_shift[10] | exp_shift[9] 
     | exp_shift[8] | exp_shift[7] | exp_shift[6];
   assign align_shift = exp_shift[5:0] | {6{exp_gt63}}; //KEP used to be all of exp_shift

   // Unpack the 52-bit mantissas to 57-bit numbers of the form.
   //    001.M[51]M[50] ... M[1]M[0]00
   // Unless the number has an exponent of zero, in which case it
   // is unpacked as
   //    000.00 ... 00
   // This effectively flushes denormalized values to zero. 
   // The three bits of to the left of the binary point prevent overflow
   // and loss of sign information. The two bits to the right of the 
   // original mantissa form the "guard" and "round" bits that are used
   // to round the result. 
   assign AddOpANormE = AddSwapE ? AddOp2NormE : AddOp1NormE;
   assign AddOpBNormE = AddSwapE ? AddOp1NormE : AddOp2NormE;
   assign mantissaA1 = {2'h0, AddOpANormE, mantissaA[51:0]&{52{AddOpANormE}}, 2'h0};
   assign mantissaB1 = {2'h0, AddOpBNormE, mantissaB[51:0]&{52{AddOpBNormE}}, 2'h0};

   // Perform mantissa alignment using a 57-bit barrel shifter 
   // If any of the bits shifted out are one, Sticky_out is set. 
   // The size of the barrel shifter could be reduced by two bits
   // by not adding the leading two zeros until after the shift. 
   barrel_shifter_r57 bs1 (mantissaB2, Sticky_out, mantissaB1, align_shift);

   // Place either the sign-extened 32-bit value or the original 64-bit value 
   // into IntValue (to be used for integer to floating point conversion)
   // assign IntValue [31:0] = FSrcXE[31:0];
   // assign IntValue [63:32] = FOpCtrlE[0] ? {32{FSrcXE[31]}} : FSrcXE[63:32];

   // If doing an integer to floating point conversion, mantissaA3 is set to 
   // IntVal and the prenomalized exponent is set to 1084. Otherwise, 
   // mantissaA3 is simply extended to 64-bits by setting the 7 LSBs to zero, 
   // and the exponent value is left unchanged. 
   // Under denormalized cases, the exponent before the rounder is set to 1
   // if the normal shift value is 11.
   assign AddConvertE       = ~FOpCtrlE[2] & FOpCtrlE[1];
   assign mantissaA3    = (FOpCtrlE[3]) ? (FOpCtrlE[0] ? AddFloat1E : ~AddFloat1E) : (AddDenormInE ? ({12'h0, mantissaA}) : (AddConvertE ? IntValue : {mantissaA1, 7'h0}));

   // Put zero in for mantissaB3, if zeroB is one. Otherwise, B is extended to 
   // 64-bits by setting the 7 LSBs to the Sticky_out bit followed by six  
   // zeros. 
   assign mantissaB3[63:7] = (FOpCtrlE[3]) ? (57'h0) : (AddDenormInE ? {12'h0, mantissaB[51:7]} : mantissaB2 & {57{~zeroB}});
   assign mantissaB3[6]    = (FOpCtrlE[3]) ? (1'b0) : (AddDenormInE ? mantissaB[6] : Sticky_out & ~zeroB);
   assign mantissaB3[5:0]  = (FOpCtrlE[3]) ? (6'h01) : (AddDenormInE ? mantissaB[5:0] : 6'h0);

   // The sign of the result needs to be corrected if the true
   // operation is subtraction and the input operands were swapped. 
   assign AddCorrSignE = ~FOpCtrlE[2]&~FOpCtrlE[1]&FOpCtrlE[0]&AddSwapE;

   // 64-bit Mantissa Adder/Subtractor
   cla64 add1 (AddSumE, mantissaA3, mantissaB3, sub); //***adder

   // 64-bit Mantissa Subtractor - to get the two's complement of the 
   // result when the sign from the adder/subtractor is negative. 
   cla_sub64 sub1 (AddSumTcE, mantissaB3, mantissaA3); //***adder
 
   // Finds normal underflow result to determine whether to round final exponent down
   //***KEP used to be (AddSumE == 16'h0) I am unsure what it's supposed to be
   assign AddNormOvflowE = (AddDenormInE & (AddSumE == 64'h0) & (AddOpANormE | AddOpBNormE) & ~FOpCtrlE[0]) ? 1'b1 : (AddSumE[63] ? AddSumTcE[52] : AddSumE[52]);

endmodule // fpadd


//
// File name : fpadd
// Title     : Floating-Point Adder/Subtractor
// project   : FPU
// Library   : fpadd
// Author(s) : James E. Stine, Jr., Brett Mathis
// Purpose   : definition of main unit to floating-point add/sub
// notes :   
//
// Copyright Oklahoma State University
// Copyright AFRL
//
// Basic and Denormalized Operations
//
// Step 1: Load operands, set flags, and AddConvertM SP to DP
// Step 2: Check for special inputs ( +/- Infinity,  NaN)
// Step 3: Compare exponents.  Swap the operands of exp1 < exp2
//         or of (exp1 = exp2 AND mnt1 < mnt2)
// Step 4: Shift the mantissa corresponding to the smaller AddExponentM, 
//          and extend precision by three bits to the right.
// Step 5: Add or subtract the mantissas.
// Step 6: Normalize the result.//
//   Shift left until normalized.  Normalized when the value to the 
//   left of the binrary point is 1.
// Step 7: Round the result.// 
// Step 8: Put AddSumM onto output.
//


module fpuaddcvt2 (
   input [2:0] 	FrmM,		// Rounding mode - specify values 
   input [3:0]	FOpCtrlM,	// Function opcode
   input 	FmtM,   		// Result Precision (0 for double, 1 for single)
   input [63:0] AddSumM, AddSumTcM,
   input [63:0] 	 AddFloat1M, 
   input [63:0] 	 AddFloat2M,
   input [11:0]	 AddExp1DenormM, AddExp2DenormM,
   input [10:0] 	 AddExponentM, AddExpPostSumM,
   input [3:0] 	 AddSelInvM,
   input		 AddOp1NormM, AddOp2NormM,
   input		 AddOpANormM, AddOpBNormM,
   input		 AddInvalidM,
   input 	 AddDenormInM, 
   input 	 AddSignAM, 
   input         AddCorrSignM,
   input 	 AddConvertM,
   input          AddSwapM,

   output [63:0] FAddResM,	// Result of operation
   output [4:0]  FAddFlgM   	// IEEE exception flags 
);
   wire 	 AddDenormM;   	// AddDenormM on input or output   

   wire          P;
   assign P = ~FmtM;

   wire [10:0]   exp_pre;
   wire [63:0] 	 Result;   
   wire [63:0] 	 sum_norm, sum_norm_w_bypass;
   wire [5:0] 	 norm_shift, norm_shift_denorm;
   wire          exp_valid;
   wire		 DenormIO;
   wire [4:0] 	 FlagsIn;	
   wire 	 Sticky_out;
   wire 	 sign_corr;
   wire 	 zeroB;         
   wire 	 mantissa_comp;
   wire 	 mantissa_comp_sum;
   wire 	 mantissa_comp_sum_tc;
   wire 	 Float1_sum_comp;
   wire 	 Float2_sum_comp;
   wire 	 Float1_sum_tc_comp;
   wire 	 Float2_sum_tc_comp;
   wire 	 normal_underflow;
   wire [63:0]   sum_corr;
   logic AddNormOvflowM;
 
 
   logic 	AddOvEnM;		// Overflow trap enabled
   logic 	AddUnEnM;   	// Underflow trap enabled

   assign AddOvEnM = 1'b1;
   assign AddUnEnM = 1'b1;
   //AddExponentM value pre-rounding with considerations for denormalized
   //cases/conversion cases
   assign exp_pre       = AddDenormInM ?
                          ((norm_shift == 6'b001011) ? 11'b00000000001 : (AddSwapM ? AddExp2DenormM[10:0] : AddExp1DenormM[10:0]))
                          : (AddConvertM ? 11'b10000111100 : AddExponentM);


   // Finds normal underflow result to determine whether to round final AddExponentM down
   // Comparison between each float and the resulting AddSumM of the primary cla adder/subtractor and cla subtractor
   assign Float1_sum_comp = (AddFloat1M[51:0] > AddSumM[51:0]) ? 1'b0 : 1'b1;
   assign Float2_sum_comp = (AddFloat2M[51:0] > AddSumM[51:0]) ? 1'b0 : 1'b1;
   assign Float1_sum_tc_comp = (AddFloat1M[51:0] > AddSumTcM[51:0]) ? 1'b0 : 1'b1;
   assign Float2_sum_tc_comp = (AddFloat2M[51:0] > AddSumTcM[51:0]) ? 1'b0 : 1'b1;

   // Determines the correct Float value to compare based on AddSwapM result
   assign mantissa_comp_sum = AddSwapM ? Float2_sum_comp : Float1_sum_comp;
   assign mantissa_comp_sum_tc = AddSwapM ? Float2_sum_tc_comp : Float1_sum_tc_comp;

   // Determines the correct comparison result based on operation and sign of resulting AddSumM
   assign mantissa_comp = (FOpCtrlM[0] ^ AddSumM[63]) ? mantissa_comp_sum_tc : mantissa_comp_sum;

   // If the signs are different and both operands aren't denormalized
   // the normal underflow bit is needed and therefore updated.
   assign normal_underflow = ((AddFloat1M[63] ~^ AddFloat2M[63]) & (AddOpANormM | AddOpBNormM)) ? mantissa_comp : 1'b0;

   // Determine the correct sign of the result
   assign sign_corr = ((AddCorrSignM ^ AddSignAM) & ~AddConvertM) ^ AddSumM[63];   
   
   // If the AddSumM is negative, use its two complement instead. 
   // This value has to be 64-bits to correctly handle the 
   // case 10...00
   assign sum_corr = (AddDenormInM & (AddOpANormM | AddOpBNormM) & ( ( (AddFloat1M[63] ~^ AddFloat2M[63]) & FOpCtrlM[0] ) | ((AddFloat1M[63] ^ AddFloat2M[63]) & ~FOpCtrlM[0]) ))
			 ? (AddSumM[63] ? AddSumM : AddSumTcM) : ( (FOpCtrlM[3]) ? AddSumM : (AddSumM[63] ? AddSumTcM : AddSumM));

   // Finds normal underflow result to determine whether to round final AddExponentM down
   //KEP used to be (AddSumM == 16'h0) not sure what it is supposed to be
   assign AddNormOvflowM = (AddDenormInM & (AddSumM == 64'h0) & (AddOpANormM | AddOpBNormM) & ~FOpCtrlM[0]) ? 1'b1 : (AddSumM[63] ? AddSumTcM[52] : AddSumM[52]);

   // Leading-Zero Detector. Determine the size of the shift needed for
   // normalization. If sum_corrected is all zeros, the exp_valid is 
   // zero; otherwise, it is one. 
   lz64 lzd1 (norm_shift, exp_valid, sum_corr);

   assign norm_shift_denorm = (AddDenormInM & ( (~AddOpANormM & ~AddOpBNormM) | normal_underflow)) ? (6'h00) : (norm_shift);

   // Barell shifter used for normalization. It takes as inputs the 
   // the corrected AddSumM and the amount by which the AddSumM should 
   // be right shifted. It outputs the normalized AddSumM. 
   barrel_shifter_l64 bs2 (sum_norm, sum_corr, norm_shift_denorm);
  
   assign sum_norm_w_bypass = (FOpCtrlM[3]) ? (FOpCtrlM[0] ? ~sum_corr : sum_corr) : (sum_norm);

   // Round the mantissa to a 52-bit value, with the leading one
   // removed. If the result is a single precision number, the actual 
   // mantissa is in the upper 23 bits and the lower 29 bits are zero. 
   // At this point, normalization has already been performed, so we know 
   // exactly where the rounding point is. The rounding units also
   // handles special cases and set the exception flags.

   // Changed DenormIO -> AddDenormM and FlagsIn -> FAddFlgM in order to
   // help in processor reservation station detection of load/stores. In
   // other words, the processor would like to know ahead of time that
   // if the result is an exception then don't load or store.
   rounder round1 (Result, DenormIO, FlagsIn, FrmM, P, AddOvEnM, AddUnEnM, exp_valid, 
		   AddSelInvM, AddInvalidM, AddDenormInM, AddConvertM, sign_corr, exp_pre, norm_shift, sum_norm_w_bypass,
		   AddExpPostSumM, AddOp1NormM, AddOp2NormM, AddFloat1M[63:52], AddFloat2M[63:52],
		   AddNormOvflowM, normal_underflow, AddSwapM, FOpCtrlM, AddSumM);

   // Store the final result and the exception flags in registers.
   assign FAddResM = Result;
   assign {AddDenormM, FAddFlgM} = {DenormIO, FlagsIn};
   
endmodule // fpadd