diff --git a/stint/private/datatypes.nim b/stint/private/datatypes.nim
index 86760e0..987af07 100644
--- a/stint/private/datatypes.nim
+++ b/stint/private/datatypes.nim
@@ -82,26 +82,26 @@ iterator leastToMostSig*(limbs: var Limbs): var Word =
 iterator leastToMostSig*(aLimbs, bLimbs: Limbs): (Word, Word) =
   ## Iterate from least to most significant word
   when cpuEndian == littleEndian:
-    for i in 0 ..< limbs.len:
+    for i in 0 ..< aLimbs.len:
       yield (aLimbs[i], bLimbs[i])
   else:
-    for i in countdown(limbs.len-1, 0):
+    for i in countdown(aLimbs.len-1, 0):
       yield (aLimbs[i], bLimbs[i])
 
 iterator leastToMostSig*(aLimbs: var Limbs, bLimbs: Limbs): (var Word, Word) =
   ## Iterate from least to most significant word
   when cpuEndian == littleEndian:
-    for i in 0 ..< limbs.len:
+    for i in 0 ..< aLimbs.len:
       yield (aLimbs[i], bLimbs[i])
   else:
-    for i in countdown(limbs.len-1, 0):
+    for i in countdown(aLimbs.len-1, 0):
       yield (aLimbs[i], bLimbs[i])
 
 iterator leastToMostSig*(cLimbs: var Limbs, aLimbs: Limbs, bLimbs: Limbs): (var Word, Word, Word) =
   ## Iterate from least to most significant word
   when cpuEndian == littleEndian:
-    for i in 0 ..< limbs.len:
+    for i in 0 ..< aLimbs.len:
       yield (cLimbs[i], aLimbs[i], bLimbs[i])
   else:
-    for i in countdown(limbs.len-1, 0):
+    for i in countdown(aLimbs.len-1, 0):
       yield (cLimbs[i], aLimbs[i], bLimbs[i])
diff --git a/stint/private/uint_addsub.nim b/stint/private/uint_addsub.nim
index c4f11bc..135a1b2 100644
--- a/stint/private/uint_addsub.nim
+++ b/stint/private/uint_addsub.nim
@@ -7,36 +7,40 @@
 #
 # at your option. This file may not be copied, modified, or distributed except according to those terms.
 
-import  ./conversion, ./initialization,
-        ./datatypes,
-        ./uint_comparison,
-        ./uint_bitwise_ops
+import
+  ./datatypes, ./uint_comparison, ./uint_bitwise_ops,
+  ./primitives/addcarry_subborrow
 
 # ############ Addition & Substraction ############ #
+{.push raises: [], inline, noInit, gcsafe.}
 
-func `+`*(x, y: UintImpl): UintImpl {.inline.}
-  # Forward declaration
-
-func `+=`*(x: var UintImpl, y: UintImpl) {.inline.}=
-  ## In-place addition for multi-precision unsigned int
-  type SubTy = type x.lo
-  x.lo += y.lo
-  x.hi += (x.lo < y.lo).toSubtype(SubTy) + y.hi # This helps the compiler produce ADC (add with carry)
-
-func `+`*(x, y: UintImpl): UintImpl {.inline.}=
+func `+`*(x, y: Limbs): Limbs =
   # Addition for multi-precision unsigned int
-  result = x
-  result += y
+  var carry = Carry(0)
+  for wr, wx, wy in leastToMostSig(result, x, y):
+    addC(carry, wr, wx, wy, carry)
 
-func `-`*(x, y: UintImpl): UintImpl {.inline.}=
+func `+=`*(x: var Limbs, y: Limbs) =
+  ## In-place addition for multi-precision unsigned int
+  var carry = Carry(0)
+  for wx, wy in leastToMostSig(x, y):
+    addC(carry, wx, wx, wy, carry)
+
+func `-`*(x, y: Limbs): Limbs =
   # Substraction for multi-precision unsigned int
-  type SubTy = type x.lo
-  result.lo = x.lo - y.lo
-  result.hi = x.hi - y.hi - (x.lo < y.lo).toSubtype(SubTy) # This might (?) help the compiler produce SBB (sub with borrow)
+  var borrow = Borrow(0)
+  for wr, wx, wy in leastToMostSig(result, x, y):
+    subB(borrow, wr, wx, wy, borrow)
 
-func `-=`*(x: var UintImpl, y: UintImpl) {.inline.}=
+func `-=`*(x: var Limbs, y: Limbs) =
   ## In-place substraction for multi-precision unsigned int
-  x = x - y
+  var borrow = Borrow(0)
+  for wx, wy in leastToMostSig(x, y):
+    subB(borrow, wx, wx, wy, borrow)
 
-func inc*(x: var UintImpl){.inline.}=
-  x += one(type x)
+func inc*(x: var Limbs, w: SomeUnsignedInt = 1) =
+  var carry = Carry(0)
+  when cpuEndian == littleEndian:
+    addC(carry, x[0], x[0], w, carry)
+    for i in 1 ..< x.len:
+      addC(carry, x[i], x[i], 0, carry)
diff --git a/stint/private/uint_bitwise_ops.nim b/stint/private/uint_bitwise_ops.nim
index 49e6088..0afff9f 100644
--- a/stint/private/uint_bitwise_ops.nim
+++ b/stint/private/uint_bitwise_ops.nim
@@ -9,27 +9,29 @@
 
 import  ./datatypes
 
-func `not`*(x: Limbs): Limbs {.inline.}=
+{.push raises: [], inline, noInit, gcsafe.}
+
+func `not`*(x: Limbs): Limbs =
   ## Bitwise complement of unsigned integer x
   for wr, wx in leastToMostSig(result, x):
     wr = not wx
 
-func `or`*(x, y: Limbs): Limbs {.inline.}=
+func `or`*(x, y: Limbs): Limbs =
   ## `Bitwise or` of numbers x and y
   for wr, wx, wy in leastToMostSig(result, x, y):
     wr = wx or wy
 
-func `and`*(x, y: Limbs): Limbs {.inline.}=
+func `and`*(x, y: Limbs): Limbs =
   ## `Bitwise and` of numbers x and y
   for wr, wx, wy in leastToMostSig(result, x, y):
     wr = wx and wy
 
-func `xor`*(x, y: Limbs): Limbs {.inline.}=
+func `xor`*(x, y: Limbs): Limbs =
   ## `Bitwise xor` of numbers x and y
   for wr, wx, wy in leastToMostSig(result, x, y):
     wr = wx xor wy
 
-func `shr`*(x: Limbs, k: SomeInteger): Limbs {.inline.} =
+func `shr`*(x: Limbs, k: SomeInteger): Limbs =
   ## Shift right by k.
   ##
   ## k MUST be less than the base word size (2^32 or 2^64)
@@ -46,7 +48,7 @@ func `shr`*(x: Limbs, k: SomeInteger): Limbs {.inline.} =
       result[i] = (x[i] shr k) or (x[i-1] shl (WordBitWidth - k))
     result[0] = x[0] shr k
 
-func `shl`*(x: Limbs, k: SomeInteger): Limbs {.inline.}=
+func `shl`*(x: Limbs, k: SomeInteger): Limbs =
   ## Compute the `shift left` operation of x and k
   when cpuEndian == littleEndian:
     result[0] = x[0] shl k
diff --git a/stint/private/uint_comparison.nim b/stint/private/uint_comparison.nim
index eafa9b0..48832da 100644
--- a/stint/private/uint_comparison.nim
+++ b/stint/private/uint_comparison.nim
@@ -11,16 +11,18 @@ import
   ./datatypes,
   ./primitives/addcarry_subborrow
 
-func isZero*(n: SomeUnsignedInt): bool {.inline.} =
+{.push raises: [], inline, noInit, gcsafe.}
+
+func isZero*(n: SomeUnsignedInt): bool =
   n == 0
 
-func isZero*(limbs: Limbs): bool {.inline.} =
+func isZero*(limbs: Limbs): bool =
   for word in limbs:
     if not word.isZero():
       return false
   return true
 
-func `<`*(x, y: Limbs): bool {.inline.}=
+func `<`*(x, y: Limbs): bool =
   # Lower comparison for multi-precision integers
   var diff: Word
   var borrow: Borrow
@@ -28,25 +30,25 @@ func `<`*(x, y: Limbs): bool {.inline.}=
     subB(borrow, diff, wx, wy, borrow)
   return bool(borrow)
 
-func `==`*(x, y: Limbs): bool {.inline.}=
+func `==`*(x, y: Limbs): bool =
   # Equal comparison for multi-precision integers
   for wx, wy in leastToMostSig(x, y):
     if wx != wy:
       return false
   return true
 
-func `<=`*(x, y: Limbs): bool {.inline.}=
+func `<=`*(x, y: Limbs): bool =
   # Lower or equal comparison for multi-precision integers
   not(y < x)
 
-func isEven*(x: SomeUnsignedInt): bool {.inline.} =
+func isEven*(x: SomeUnsignedInt): bool =
   (x and 1) == 0
 
-func isEven*(x: Limbs): bool {.inline.}=
+func isEven*(x: Limbs): bool =
   x.leastSignificantWord.isEven
 
-func isOdd*(x: SomeUnsignedInt): bool {.inline.} =
+func isOdd*(x: SomeUnsignedInt): bool =
   not x.isEven
 
-func isOdd*(x: Limbs): bool {.inline.}=
+func isOdd*(x: Limbs): bool =
   not x.isEven