diff --git a/core/math/big/basic.odin b/core/math/big/basic.odin
index b6c49a5fd..6d1ab23e6 100644
--- a/core/math/big/basic.odin
+++ b/core/math/big/basic.odin
@@ -297,36 +297,7 @@ int_gcd_lcm :: proc(res_gcd, res_lcm, a, b: ^Int) -> (err: Error) {
 	if res_gcd == nil && res_lcm == nil { return nil; }
 	if err = clear_if_uninitialized(res_gcd, res_lcm, a, b); err != nil { return err; }
 
-	az, _ := is_zero(a); bz, _ := is_zero(b);
-	if az && bz {
-		if res_gcd != nil {
-			if err = zero(res_gcd); err != nil { return err; }
-		}
-		if res_lcm != nil {
-			if err = zero(res_lcm); err != nil { return err; }
-		}
-		return nil;
-	}
-	else if az {
-		if res_gcd != nil {
-			if err = abs(res_gcd, b); err != nil { return err; }
-		}
-		if res_lcm != nil {
-			if err = zero(res_lcm);   err != nil { return err; }
-		}
-		return nil;
-	}
-	else if bz {
-		if res_gcd != nil {
-			if err = abs(res_gcd, a); err != nil { return err; }
-		}
-		if res_lcm != nil {
-			if err = zero(res_lcm);   err != nil { return err; }
-		}
-		return nil;
-	}
-
-	return #force_inline _int_gcd_lcm(res_gcd, res_lcm, a, b);
+	return #force_inline internal_int_gcd_lcm(res_gcd, res_lcm, a, b);
 }
 gcd_lcm :: proc { int_gcd_lcm, };
 
@@ -346,171 +317,6 @@ int_lcm :: proc(res, a, b: ^Int) -> (err: Error) {
 }
 lcm :: proc { int_lcm, };
 
-/*
-	Internal function computing both GCD using the binary method,
-	and, if target isn't `nil`, also LCM.
-	Expects the arguments to have been initialized.
-*/
-_int_gcd_lcm :: proc(res_gcd, res_lcm, a, b: ^Int) -> (err: Error) {
-	/*
-		If both `a` and `b` are zero, return zero.
-		If either `a` or `b`, return the other one.
-
-		The `gcd` and `lcm` wrappers have already done this test,
-		but `gcd_lcm` wouldn't have, so we still need to perform it.
-
-		If neither result is wanted, we have nothing to do.
-	*/
-	if res_gcd == nil && res_lcm == nil { return nil; }
-
-	/*
-		We need a temporary because `res_gcd` is allowed to be `nil`.
-	*/
-	az, _ := is_zero(a); bz, _ := is_zero(b);
-	if az && bz {
-		/*
-			GCD(0, 0) and LCM(0, 0) are both 0.
-		*/
-		if res_gcd != nil {
-			if err = zero(res_gcd);	err != nil { return err; }
-		}
-		if res_lcm != nil {
-			if err = zero(res_lcm);	err != nil { return err; }
-		}
-		return nil;
-	} else if az {
-		/*
-			We can early out with GCD = B and LCM = 0
-		*/
-		if res_gcd != nil {
-			if err = abs(res_gcd, b); err != nil { return err; }
-		}
-		if res_lcm != nil {
-			if err = zero(res_lcm); err != nil { return err; }
-		}
-		return nil;
-	} else if bz {
-		/*
-			We can early out with GCD = A and LCM = 0
-		*/
-		if res_gcd != nil {
-			if err = abs(res_gcd, a); err != nil { return err; }
-		}
-		if res_lcm != nil {
-			if err = zero(res_lcm); err != nil { return err; }
-		}
-		return nil;
-	}
-
-	temp_gcd_res := &Int{};
-	defer destroy(temp_gcd_res);
-
-	/*
-		If neither `a` or `b` was zero, we need to compute `gcd`.
- 		Get copies of `a` and `b` we can modify.
- 	*/
-	u, v := &Int{}, &Int{};
-	defer destroy(u, v);
-	if err = copy(u, a); err != nil { return err; }
-	if err = copy(v, b); err != nil { return err; }
-
- 	/*
- 		Must be positive for the remainder of the algorithm.
- 	*/
-	u.sign = .Zero_or_Positive; v.sign = .Zero_or_Positive;
-
- 	/*
- 		B1.  Find the common power of two for `u` and `v`.
- 	*/
- 	u_lsb, _ := count_lsb(u);
- 	v_lsb, _ := count_lsb(v);
- 	k        := min(u_lsb, v_lsb);
-
-	if k > 0 {
-		/*
-			Divide the power of two out.
-		*/
-		if err = shr(u, u, k); err != nil { return err; }
-		if err = shr(v, v, k); err != nil { return err; }
-	}
-
-	/*
-		Divide any remaining factors of two out.
-	*/
-	if u_lsb != k {
-		if err = shr(u, u, u_lsb - k); err != nil { return err; }
-	}
-	if v_lsb != k {
-		if err = shr(v, v, v_lsb - k); err != nil { return err; }
-	}
-
-	for v.used != 0 {
-		/*
-			Make sure `v` is the largest.
-		*/
-		if c, _ := cmp_mag(u, v); c == 1 {
-			/*
-				Swap `u` and `v` to make sure `v` is >= `u`.
-			*/
-			swap(u, v);
-		}
-
-		/*
-			Subtract smallest from largest.
-		*/
-		if err = sub(v, v, u); err != nil { return err; }
-
-		/*
-			Divide out all factors of two.
-		*/
-		b, _ := count_lsb(v);
-		if err = shr(v, v, b); err != nil { return err; }
-	}
-
- 	/*
- 		Multiply by 2**k which we divided out at the beginning.
- 	*/
- 	if err = shl(temp_gcd_res, u, k); err != nil { return err; }
- 	temp_gcd_res.sign = .Zero_or_Positive;
-
-	/*
-		We've computed `gcd`, either the long way, or because one of the inputs was zero.
-		If we don't want `lcm`, we're done.
-	*/
-	if res_lcm == nil {
-		swap(temp_gcd_res, res_gcd);
-		return nil;
-	}
-
-	/*
-		Computes least common multiple as `|a*b|/gcd(a,b)`
-		Divide the smallest by the GCD.
-	*/
-	if c, _ := cmp_mag(a, b); c == -1 {
-		/*
-			Store quotient in `t2` such that `t2 * b` is the LCM.
-		*/
-		if err = div(res_lcm, a, temp_gcd_res); err != nil { return err; }
-		err = mul(res_lcm, res_lcm, b);
-	} else {
-		/*
-			Store quotient in `t2` such that `t2 * a` is the LCM.
-		*/
-		if err = div(res_lcm, a, temp_gcd_res); err != nil { return err; }
-		err = mul(res_lcm, res_lcm, b);
-	}
-
-	if res_gcd != nil {
-		swap(temp_gcd_res, res_gcd);
-	}
-
-	/*
-		Fix the sign to positive and return.
-	*/
-	res_lcm.sign = .Zero_or_Positive;
-	return err;
-}
-
 /*
 	remainder = numerator % (1 << bits)
 */
diff --git a/core/math/big/internal.odin b/core/math/big/internal.odin
index a3e2548db..995f37000 100644
--- a/core/math/big/internal.odin
+++ b/core/math/big/internal.odin
@@ -680,7 +680,7 @@ internal_int_divmod :: proc(quotient, remainder, numerator, denominator: ^Int, a
 		// err = _int_div_recursive(quotient, remainder, numerator, denominator);
 	} else {
 		when true {
-			err = _private_int_div_school(quotient, remainder, numerator, denominator);
+			err = #force_inline _private_int_div_school(quotient, remainder, numerator, denominator);
 		} else {
 			/*
 				NOTE(Jeroen): We no longer need or use `_private_int_div_small`.
@@ -864,6 +864,18 @@ internal_int_factorial :: proc(res: ^Int, n: int) -> (err: Error) {
 	return nil;
 }
 
+/*
+	Returns GCD, LCM or both.
+
+	Assumes `a` and `b` to have been initialized.
+	`res_gcd` and `res_lcm` can be nil or ^Int depending on which results are desired.
+*/
+internal_int_gcd_lcm :: proc(res_gcd, res_lcm, a, b: ^Int) -> (err: Error) {
+	if res_gcd == nil && res_lcm == nil { return nil; }
+
+	return #force_inline _private_int_gcd_lcm(res_gcd, res_lcm, a, b);
+}
+
 
 internal_int_zero_unused :: #force_inline proc(dest: ^Int, old_used := -1) {
 	/*
@@ -1466,6 +1478,171 @@ _private_int_recursive_product :: proc(res: ^Int, start, stop: int, level := int
 	return #force_inline set(res, 1);
 }
 
+/*
+	Internal function computing both GCD using the binary method,
+		and, if target isn't `nil`, also LCM.
+
+	Expects the `a` and `b` to have been initialized
+		and one or both of `res_gcd` or `res_lcm` not to be `nil`.
+
+	If both `a` and `b` are zero, return zero.
+	If either `a` or `b`, return the other one.
+
+	The `gcd` and `lcm` wrappers have already done this test,
+	but `gcd_lcm` wouldn't have, so we still need to perform it.
+
+	If neither result is wanted, we have nothing to do.
+*/
+_private_int_gcd_lcm :: proc(res_gcd, res_lcm, a, b: ^Int) -> (err: Error) {
+	if res_gcd == nil && res_lcm == nil { return nil; }
+
+	/*
+		We need a temporary because `res_gcd` is allowed to be `nil`.
+	*/
+	if a.used == 0 && b.used == 0 {
+		/*
+			GCD(0, 0) and LCM(0, 0) are both 0.
+		*/
+		if res_gcd != nil {
+			if err = zero(res_gcd);	err != nil { return err; }
+		}
+		if res_lcm != nil {
+			if err = zero(res_lcm);	err != nil { return err; }
+		}
+		return nil;
+	} else if a.used == 0 {
+		/*
+			We can early out with GCD = B and LCM = 0
+		*/
+		if res_gcd != nil {
+			if err = abs(res_gcd, b); err != nil { return err; }
+		}
+		if res_lcm != nil {
+			if err = zero(res_lcm); err != nil { return err; }
+		}
+		return nil;
+	} else if b.used == 0 {
+		/*
+			We can early out with GCD = A and LCM = 0
+		*/
+		if res_gcd != nil {
+			if err = abs(res_gcd, a); err != nil { return err; }
+		}
+		if res_lcm != nil {
+			if err = zero(res_lcm); err != nil { return err; }
+		}
+		return nil;
+	}
+
+	temp_gcd_res := &Int{};
+	defer destroy(temp_gcd_res);
+
+	/*
+		If neither `a` or `b` was zero, we need to compute `gcd`.
+ 		Get copies of `a` and `b` we can modify.
+ 	*/
+	u, v := &Int{}, &Int{};
+	defer destroy(u, v);
+	if err = copy(u, a); err != nil { return err; }
+	if err = copy(v, b); err != nil { return err; }
+
+ 	/*
+ 		Must be positive for the remainder of the algorithm.
+ 	*/
+	u.sign = .Zero_or_Positive; v.sign = .Zero_or_Positive;
+
+ 	/*
+ 		B1.  Find the common power of two for `u` and `v`.
+ 	*/
+ 	u_lsb, _ := count_lsb(u);
+ 	v_lsb, _ := count_lsb(v);
+ 	k        := min(u_lsb, v_lsb);
+
+	if k > 0 {
+		/*
+			Divide the power of two out.
+		*/
+		if err = shr(u, u, k); err != nil { return err; }
+		if err = shr(v, v, k); err != nil { return err; }
+	}
+
+	/*
+		Divide any remaining factors of two out.
+	*/
+	if u_lsb != k {
+		if err = shr(u, u, u_lsb - k); err != nil { return err; }
+	}
+	if v_lsb != k {
+		if err = shr(v, v, v_lsb - k); err != nil { return err; }
+	}
+
+	for v.used != 0 {
+		/*
+			Make sure `v` is the largest.
+		*/
+		if c, _ := cmp_mag(u, v); c == 1 {
+			/*
+				Swap `u` and `v` to make sure `v` is >= `u`.
+			*/
+			swap(u, v);
+		}
+
+		/*
+			Subtract smallest from largest.
+		*/
+		if err = sub(v, v, u); err != nil { return err; }
+
+		/*
+			Divide out all factors of two.
+		*/
+		b, _ := count_lsb(v);
+		if err = shr(v, v, b); err != nil { return err; }
+	}
+
+ 	/*
+ 		Multiply by 2**k which we divided out at the beginning.
+ 	*/
+ 	if err = shl(temp_gcd_res, u, k); err != nil { return err; }
+ 	temp_gcd_res.sign = .Zero_or_Positive;
+
+	/*
+		We've computed `gcd`, either the long way, or because one of the inputs was zero.
+		If we don't want `lcm`, we're done.
+	*/
+	if res_lcm == nil {
+		swap(temp_gcd_res, res_gcd);
+		return nil;
+	}
+
+	/*
+		Computes least common multiple as `|a*b|/gcd(a,b)`
+		Divide the smallest by the GCD.
+	*/
+	if c, _ := cmp_mag(a, b); c == -1 {
+		/*
+			Store quotient in `t2` such that `t2 * b` is the LCM.
+		*/
+		if err = div(res_lcm, a, temp_gcd_res); err != nil { return err; }
+		err = mul(res_lcm, res_lcm, b);
+	} else {
+		/*
+			Store quotient in `t2` such that `t2 * a` is the LCM.
+		*/
+		if err = div(res_lcm, a, temp_gcd_res); err != nil { return err; }
+		err = mul(res_lcm, res_lcm, b);
+	}
+
+	if res_gcd != nil {
+		swap(temp_gcd_res, res_gcd);
+	}
+
+	/*
+		Fix the sign to positive and return.
+	*/
+	res_lcm.sign = .Zero_or_Positive;
+	return err;
+}
+
 /*	
 	========================    End of private procedures    =======================
 
diff --git a/core/math/big/test.py b/core/math/big/test.py
index a06e8e119..6bdff91db 100644
--- a/core/math/big/test.py
+++ b/core/math/big/test.py
@@ -446,7 +446,6 @@ TESTS = {
 	test_factorial: [
 		[  6_000 ],   # Regular factorial, see cutoff in common.odin.
 		[ 12_345 ],   # Binary split factorial
-		[ 100_000 ],
 	],
 	test_gcd: [
 		[  23, 25, ],
@@ -464,6 +463,12 @@ TESTS = {
 	],
 }
 
+if not FAST_TESTS:
+	TESTS[test_factorial].append(
+		# This one on its own takes around 800ms, so we exclude it for FAST_TESTS
+		[ 100_000 ],
+	)
+
 total_passes   = 0
 total_failures = 0