From 4c106215f44cecc055a2e88fe47d0b683d0282e0 Mon Sep 17 00:00:00 2001
From: David Harris <David_Harris@hmc.edu>
Date: Fri, 10 Nov 2023 08:46:55 -0800
Subject: [PATCH] Started cleaning up shifting leading 1 in fdivsqrt

---
 config/shared/config-shared.vh      | 18 +++++++++---------
 src/fpu/fdivsqrt/fdivsqrtpreproc.sv | 18 +++++++++---------
 2 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/config/shared/config-shared.vh b/config/shared/config-shared.vh
index 48f02b848..acc7996cb 100644
--- a/config/shared/config-shared.vh
+++ b/config/shared/config-shared.vh
@@ -94,15 +94,15 @@ localparam FMT2  = ((F_SUPPORTED & (LEN1 != S_LEN)) ? 2'd0    : 2'd2);
 localparam BIAS2 = ((F_SUPPORTED & (LEN1 != S_LEN)) ? S_BIAS : H_BIAS);
 
 // division constants
-localparam DIVN        = (((NF+2<XLEN) & IDIV_ON_FPU) ? XLEN : NF+2); // standard length of input
-localparam LOGR        = ($clog2(RADIX));           // r = log(R)
-localparam RK          = (LOGR*DIVCOPIES);         // r*k used for intdiv preproc
-localparam LOGRK       = ($clog2(RK));               // log2(r*k)
-localparam FPDUR       = ((DIVN+1+(LOGR*DIVCOPIES))/(LOGR*DIVCOPIES)+(RADIX/4));
-localparam DURLEN      = ($clog2(FPDUR+1));
-localparam DIVb        = (FPDUR*LOGR*DIVCOPIES-1); // canonical fdiv size (b)
-localparam DIVBLEN     = ($clog2(DIVb+1)-1);
-localparam DIVa        = (DIVb+1-XLEN); // used for idiv on fpu: Shift residual right by b - (XLEN-1) to put remainder in lsbs of integer result
+localparam DIVN        = ((NF+2<XLEN) & IDIV_ON_FPU) ? XLEN : NF+2; // standard length of input
+localparam LOGR        = $clog2(RADIX);           // r = log(R)
+localparam RK          = LOGR*DIVCOPIES;         // r*k used for intdiv preproc
+localparam LOGRK       = $clog2(RK);               // log2(r*k)
+localparam FPDUR       = (DIVN+1)/RK + 1 + (RADIX/4);
+localparam DURLEN      = $clog2(FPDUR+1);
+localparam DIVb        = FPDUR*RK - 1; // canonical fdiv size (b)
+localparam DIVBLEN     = $clog2(DIVb+1)-1;
+localparam DIVa        = DIVb+1-XLEN; // used for idiv on fpu: Shift residual right by b - (XLEN-1) to put remainder in lsbs of integer result
 
 // largest length in IEU/FPU
 localparam CVTLEN = ((NF<XLEN) ? (XLEN) : (NF));  // max(XLEN, NF)
diff --git a/src/fpu/fdivsqrt/fdivsqrtpreproc.sv b/src/fpu/fdivsqrt/fdivsqrtpreproc.sv
index 6c397576a..8f3c477c4 100644
--- a/src/fpu/fdivsqrt/fdivsqrtpreproc.sv
+++ b/src/fpu/fdivsqrt/fdivsqrtpreproc.sv
@@ -52,7 +52,7 @@ module fdivsqrtpreproc import cvw::*;  #(parameter cvw_t P) (
   logic [P.DIVb:0]             PreSqrtX;
   logic [P.DIVb+3:0]           DivX, DivXShifted, SqrtX, PreShiftX; // Variations of dividend, to be muxed
   logic [P.NE+1:0]             QeE;                                 // Quotient Exponent (FP only)
-  logic [P.DIVb-1:0]           IFX, IFD;                            // Correctly-sized inputs for iterator, selected from int or fp input
+  logic [P.DIVb:0]             IFX, IFD;                            // Correctly-sized inputs for iterator, selected from int or fp input
   logic [P.DIVBLEN:0]          mE, nE, ell;                         // Leading zeros of inputs
   logic                        NumerZeroE;                          // Numerator is zero (X or A)
   logic                        AZeroE, BZeroE;                      // A or B is Zero for integer division
@@ -89,12 +89,12 @@ module fdivsqrtpreproc import cvw::*;  #(parameter cvw_t P) (
     mux2 #(P.XLEN) posbmux(BE, -BE, BsE, PosB);
 
     // Select integer or floating point inputs
-    mux2 #(P.DIVb) ifxmux({Xm, {(P.DIVb-P.NF-1){1'b0}}}, {PosA, {(P.DIVb-P.XLEN){1'b0}}}, IntDivE, IFX);
-    mux2 #(P.DIVb) ifdmux({Ym, {(P.DIVb-P.NF-1){1'b0}}}, {PosB, {(P.DIVb-P.XLEN){1'b0}}}, IntDivE, IFD);
+    mux2 #(P.DIVb+1) ifxmux({Xm, {(P.DIVb-P.NF){1'b0}}}, {PosA, {(P.DIVb-P.XLEN+1){1'b0}}}, IntDivE, IFX);
+    mux2 #(P.DIVb+1) ifdmux({Ym, {(P.DIVb-P.NF){1'b0}}}, {PosB, {(P.DIVb-P.XLEN+1){1'b0}}}, IntDivE, IFD);
     mux2 #(1)    numzmux(XZeroE, AZeroE, IntDivE, NumerZeroE);
   end else begin // Int not supported
-    assign IFX = {Xm, {(P.DIVb-P.NF-1){1'b0}}};
-    assign IFD = {Ym, {(P.DIVb-P.NF-1){1'b0}}};
+    assign IFX = {Xm, {(P.DIVb-P.NF){1'b0}}};
+    assign IFD = {Ym, {(P.DIVb-P.NF){1'b0}}};
     assign NumerZeroE = XZeroE;
   end
 
@@ -103,12 +103,12 @@ module fdivsqrtpreproc import cvw::*;  #(parameter cvw_t P) (
   //////////////////////////////////////////////////////
 
   // count leading zeros for Subnorm FP and to normalize integer inputs
-  lzc #(P.DIVb) lzcX (IFX, ell);
-  lzc #(P.DIVb) lzcY (IFD, mE);
+  lzc #(P.DIVb) lzcX (IFX[P.DIVb:1], ell);
+  lzc #(P.DIVb) lzcY (IFD[P.DIVb:1], mE);
 
   // Normalization shift: shift off leading one
-  assign Xfract = (IFX << ell) << 1;
-  assign Dfract = (IFD << mE)  << 1; 
+  assign Xfract = (IFX[P.DIVb:1] << ell) << 1;
+  assign Dfract = (IFD[P.DIVb:1] << mE)  << 1; 
 
   //////////////////////////////////////////////////////
   // Integer Right Shift to digit boundary