div/rem bug fixes.

pk/int.c

@@ -31,7 +31,26 @@ int emulate_int(trapframe_t* tf)
   {
     if(noisy)
       printk("emulating div\n");
-    XRD = softint_divu(xrs1, xrs2);
+
+    int num_negative = 0;
+                     
+    if ((signed long) xrs1 < 0)
+    {
+      xrs1 = -xrs1;
+      num_negative++;
+    }
+                     
+    if ((signed long) xrs2 < 0)
+    {
+      xrs2 = -xrs2;
+      num_negative++;
+    }
+
+    unsigned long res = softint_divu(xrs1, xrs2);
+    if (num_negative == 1)
+      XRD = -res;
+    else
+      XRD = res;
   }
   else if(IS_INSN(DIVU))
   {
@@ -49,6 +68,10 @@ int emulate_int(trapframe_t* tf)
   {
     if(noisy)
       printk("emulating rem\n");
+
+    if ((signed long) xrs1 < 0) {xrs1 = -xrs1;}
+    if ((signed long) xrs2 < 0) {xrs2 = -xrs2;}
+
     XRD = softint_remu(xrs1, xrs2);
   }
   else if(IS_INSN(REMU))

softint/divu.c

@@ -4,42 +4,62 @@
 long 
  softint_divu( long rs1, long rs2 )
 {
-  // only designed to work for mabi=32
   // quotient = dividend / divisor + remainder
-  unsigned long long dividend = rs1;
-  unsigned long long divisor  = rs2;
+  unsigned long dividend = rs1;
+  unsigned long divisor  = rs2;
 
+  int msb = (sizeof(long) << 3) - 1;
 
   if (divisor == 0) return -1; 
 
-  unsigned long long temp_dividend = dividend;
-  unsigned long long temp_divisor = divisor;
+  unsigned long temp_dividend = dividend;
+  unsigned long temp_divisor = divisor;
 
-  unsigned long long quotient = 0;
+  unsigned long quotient = 0;
 
 
-  for (int i=0; i <= 32; i++)
+  for (int i=0; i <= msb; i++)
   {
-    unsigned long long temp_quotient = 1;
+    unsigned long temp_quotient = 1;
      
     if (temp_divisor == temp_dividend)  { quotient += 1; break;}
     else if (temp_dividend < temp_divisor) { quotient += 0; break; }
 
-    while (temp_divisor <= temp_dividend && temp_quotient != 0)
-    {
-      temp_divisor = temp_divisor << 1;
-      temp_quotient = temp_quotient << 1;
-    }
 
-    temp_divisor = temp_divisor >> 1;
-    temp_quotient = temp_quotient >> 1;
-
-      
+    // check for corner-case when (msb of dividend)==1                              
+    if ((temp_dividend & (1 << msb)) == (1 << msb))                     
+    {                                                                 
+      int hi = msb, lo = 0;                                           
+      for (int i=msb; i >= 0; i--)                                     
+      {                                                              
+        unsigned int mask = 1 << i;                                 
+        if ((mask & temp_divisor) == mask)                          
+        {                                                           
+          lo = i;                                                  
+          break;                                                   
+        }                                                           
+      }                                                              
+      temp_divisor = temp_divisor << (hi - lo - 1);                  
+      temp_quotient = temp_quotient << (hi - lo - 1);                
+    }                                                                 
+    else                                                              
+    {                                                                 
+      while (temp_divisor <= temp_dividend)                          
+      {                                                              
+        temp_divisor = temp_divisor << 1;                           
+        temp_quotient = temp_quotient << 1;                         
+      }                                                              
+                                                                     
+      temp_divisor = temp_divisor >> 1;                              
+      temp_quotient = temp_quotient >> 1;                            
+    }                                                                 
+                                                                     
+        
     temp_dividend = temp_dividend - temp_divisor;
     temp_divisor = divisor;
     quotient += temp_quotient;
   }
 
-  return (long) quotient;
+  return quotient;
 }
 

softint/remu.c

@@ -4,35 +4,53 @@
 long 
  softint_remu( long rs1, long rs2 )
 {
-  // only designed to work for mabi=32
   // quotient = dividend / divisor + remainder
-
-  unsigned long long dividend = rs1;
-  unsigned long long divisor  = rs2;
+  unsigned long dividend = rs1;
+  unsigned long divisor  = rs2;
+  
+  int msb = (sizeof(long) << 3) - 1;
 
   if (divisor == 0) { return dividend; }
 
-  long long temp_dividend = dividend;
-  long long temp_divisor = divisor;
+  unsigned long temp_dividend = dividend;
+  unsigned long temp_divisor = divisor;
 
-  for (int i=0; i <= 32; i++)
+  for (int i=0; i <= msb; i++)
   {
     if (temp_divisor == temp_dividend) { return 0; }
-    else if (temp_dividend < temp_divisor) { return (long) temp_dividend; }
-
-
-    while (temp_divisor <= temp_dividend && temp_divisor != 0)
-    {
-      temp_divisor = temp_divisor << 1;
+    else if (temp_dividend < temp_divisor) { return temp_dividend; }
+
+ 
+    // check for corner-case when (msb of dividend)==1                              
+    if ((temp_dividend & (1 << msb)) == (1 << msb))                     
+    {                                                                 
+      int hi = msb, lo = 0;                                           
+      for (int i=msb; i >= 0; i--)                                     
+      {                                                              
+        unsigned int mask = 1 << i;                                 
+        if ((mask & temp_divisor) == mask)                          
+        {                                                           
+          lo = i;                                                  
+          break;                                                   
+        }                                                           
+      }                                                              
+      temp_divisor = temp_divisor << (hi - lo - 1);                  
+    }                                                                 
+    else                                                              
+    {                                                                 
+      while ( (unsigned long) temp_divisor <= (unsigned long) temp_dividend)                          
+      {                                                              
+        temp_divisor = temp_divisor << 1;                           
+      }                                                              
+                                                                     
+      temp_divisor = temp_divisor >> 1;                              
     }
 
-    temp_divisor = temp_divisor >> 1;
-
 
     temp_dividend = temp_dividend - temp_divisor;
     temp_divisor = divisor;
   }
 
-  return (long) temp_dividend;
+  return temp_dividend;
 }