From e02c1008bc581684ef11902c1f3a54589f071bf8 Mon Sep 17 00:00:00 2001
From: David Harris <David_Harris@hmc.edu>
Date: Mon, 10 Jun 2024 07:55:35 -0700
Subject: [PATCH] postprocessor shift amount simplification

---
 src/fpu/postproc/divshiftcalc.sv | 4 ----
 src/fpu/postproc/fmashiftcalc.sv | 4 ++--
 src/fpu/postproc/postprocess.sv  | 5 ++---
 3 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/src/fpu/postproc/divshiftcalc.sv b/src/fpu/postproc/divshiftcalc.sv
index 0a222d724..d45afeea6 100644
--- a/src/fpu/postproc/divshiftcalc.sv
+++ b/src/fpu/postproc/divshiftcalc.sv
@@ -28,10 +28,8 @@
 ////////////////////////////////////////////////////////////////////////////////////////////////
 
 module divshiftcalc import cvw::*;  #(parameter cvw_t P) (
-  input  logic [P.DIVb:0]              DivUm,              // divsqrt significand
   input  logic [P.NE+1:0]              DivUe,              // divsqrt exponent
   output logic [P.LOGNORMSHIFTSZ-1:0]  DivShiftAmt,        // divsqrt shift amount
-  output logic [P.NORMSHIFTSZ-1:0]     DivShiftIn,         // divsqrt shift input
   output logic                         DivResSubnorm,      // is the divsqrt result subnormal
   output logic                         DivSubnormShiftPos  // is the subnormal shift amount positive
 );
@@ -68,6 +66,4 @@ module divshiftcalc import cvw::*;  #(parameter cvw_t P) (
   assign DivSubnormShiftAmt = DivSubnormShiftPos ? DivSubnormShift[P.LOGNORMSHIFTSZ-1:0] : '0;
   assign DivShiftAmt        = DivResSubnorm ? DivSubnormShiftAmt : NormShift;
 
-  // pre-shift the divider result for normalization
-  assign DivShiftIn = {{P.NF{1'b0}}, DivUm, {P.NORMSHIFTSZ-P.DIVb-1-P.NF{1'b0}}};
 endmodule
diff --git a/src/fpu/postproc/fmashiftcalc.sv b/src/fpu/postproc/fmashiftcalc.sv
index 1d33f7337..cf334aa9b 100644
--- a/src/fpu/postproc/fmashiftcalc.sv
+++ b/src/fpu/postproc/fmashiftcalc.sv
@@ -53,6 +53,7 @@ module fmashiftcalc import cvw::*;  #(parameter cvw_t P) (
   //convert the sum's exponent into the proper precision
   if (P.FPSIZES == 1) begin
     assign NormSumExp = PreNormSumExp;
+    assign BiasCorr = '0;
   end else if (P.FPSIZES == 2) begin
     assign BiasCorr = Fmt ? (P.NE+2)'(0) : (P.NE+2)'(P.BIAS1-P.BIAS);
     assign NormSumExp = PreNormSumExp+BiasCorr;
@@ -129,6 +130,5 @@ module fmashiftcalc import cvw::*;  #(parameter cvw_t P) (
 
   // set and calculate the shift input and amount
   //  - shift once if killing a product and the result is subnormal
-  if (P.FPSIZES == 1) assign FmaShiftAmt = FmaPreResultSubnorm ? FmaSe[$clog2(P.FMALEN-1)-1:0]+($clog2(P.FMALEN-1))'(P.NF+3): FmaSCnt+1;
-  else                assign FmaShiftAmt = FmaPreResultSubnorm ? FmaSe[$clog2(P.FMALEN-1)-1:0]+($clog2(P.FMALEN-1))'(P.NF+3)+BiasCorr[$clog2(P.FMALEN-1)-1:0]: FmaSCnt+1;
+  assign FmaShiftAmt = FmaPreResultSubnorm ? FmaSe[$clog2(P.FMALEN-1)-1:0]+($clog2(P.FMALEN-1))'(P.NF+3)+BiasCorr[$clog2(P.FMALEN-1)-1:0]: FmaSCnt+1;
 endmodule
diff --git a/src/fpu/postproc/postprocess.sv b/src/fpu/postproc/postprocess.sv
index 20968dad7..2db03cb16 100644
--- a/src/fpu/postproc/postprocess.sv
+++ b/src/fpu/postproc/postprocess.sv
@@ -91,7 +91,6 @@ module postprocess import cvw::*;  #(parameter cvw_t P) (
   logic [$clog2(P.FMALEN+1)-1:0] FmaShiftAmt;          // normalization shift amount for fma
   // division signals
   logic [P.LOGNORMSHIFTSZ-1:0] DivShiftAmt;          // divsqrt shif amount
-  logic [P.NORMSHIFTSZ-1:0]    DivShiftIn;           // divsqrt shift input
   logic [P.NE+1:0]             Ue;                   // divsqrt corrected exponent after corretion shift
   logic                        DivByZero;            // divide by zero flag
   logic                        DivResSubnorm;        // is the divsqrt result subnormal
@@ -147,7 +146,7 @@ module postprocess import cvw::*;  #(parameter cvw_t P) (
   fmashiftcalc #(P) fmashiftcalc(.FmaSCnt, .Fmt, .NormSumExp, .FmaSe, .FmaSm,
       .FmaSZero, .FmaPreResultSubnorm, .FmaShiftAmt);
 
-  divshiftcalc #(P) divshiftcalc(.DivUe, .DivUm, .DivResSubnorm, .DivSubnormShiftPos, .DivShiftAmt, .DivShiftIn);
+  divshiftcalc #(P) divshiftcalc(.DivUe, .DivResSubnorm, .DivSubnormShiftPos, .DivShiftAmt);
 
   // select which unit's output to shift
   always_comb
@@ -162,7 +161,7 @@ module postprocess import cvw::*;  #(parameter cvw_t P) (
       end
       2'b01: begin //divsqrt
         ShiftAmt = DivShiftAmt;
-        ShiftIn  =  DivShiftIn;
+        ShiftIn  = {{P.NF{1'b0}}, DivUm, {P.NORMSHIFTSZ-P.DIVb-1-P.NF{1'b0}}};
       end
       default: begin 
         ShiftAmt = {P.LOGNORMSHIFTSZ{1'bx}};