LibJS/Bytecode: Increase coverage of left/shift expression fast paths

As long as the inputs are Int32, we can convert them to UInt32 in a
spec-compliant way with a simple static_cast<u32>.

This allows calculations like `-3 >>> 2` to take the fast path as well,
which is extremely valuable for stuff like crypto code.

While we're doing this, also remove the fast paths from the generic
shift functions in Value.cpp, since we only end up there if we *didn't*
take the same fast path in the interpreter.

Userland/Libraries/LibJS/Bytecode/Interpreter.cpp

@@ -841,7 +841,7 @@ ThrowCompletionOr<void> UnsignedRightShift::execute_impl(Bytecode::Interpreter&
     auto& vm = interpreter.vm();
     auto const lhs = interpreter.get(m_lhs);
     auto const rhs = interpreter.get(m_rhs);
-    if (lhs.is_int32() && rhs.is_int32() && lhs.as_i32() >= 0 && rhs.as_i32() >= 0) {
+    if (lhs.is_int32() && rhs.is_int32()) {
         auto const shift_count = static_cast<u32>(rhs.as_i32()) % 32;
         interpreter.set(m_dst, Value(static_cast<u32>(lhs.as_i32()) >> shift_count));
         return {};
@@ -855,7 +855,7 @@ ThrowCompletionOr<void> RightShift::execute_impl(Bytecode::Interpreter& interpre
     auto& vm = interpreter.vm();
     auto const lhs = interpreter.get(m_lhs);
     auto const rhs = interpreter.get(m_rhs);
-    if (lhs.is_int32() && rhs.is_int32() && rhs.as_i32() >= 0) {
+    if (lhs.is_int32() && rhs.is_int32()) {
         auto const shift_count = static_cast<u32>(rhs.as_i32()) % 32;
         interpreter.set(m_dst, Value(lhs.as_i32() >> shift_count));
         return {};
@@ -869,7 +869,7 @@ ThrowCompletionOr<void> LeftShift::execute_impl(Bytecode::Interpreter& interpret
     auto& vm = interpreter.vm();
     auto const lhs = interpreter.get(m_lhs);
     auto const rhs = interpreter.get(m_rhs);
-    if (lhs.is_int32() && rhs.is_int32() && rhs.as_i32() >= 0) {
+    if (lhs.is_int32() && rhs.is_int32()) {
         auto const shift_count = static_cast<u32>(rhs.as_i32()) % 32;
         interpreter.set(m_dst, Value(lhs.as_i32() << shift_count));
         return {};

Userland/Libraries/LibJS/Runtime/Value.cpp

@@ -1598,12 +1598,6 @@ ThrowCompletionOr<Value> left_shift(VM& vm, Value lhs, Value rhs)
 // ShiftExpression : ShiftExpression >> AdditiveExpression
 ThrowCompletionOr<Value> right_shift(VM& vm, Value lhs, Value rhs)
 {
-    // OPTIMIZATION: Fast path when both values are suitable Int32 values.
-    if (lhs.is_int32() && rhs.is_int32() && rhs.as_i32() >= 0) {
-        auto shift_count = static_cast<u32>(rhs.as_i32()) % 32;
-        return Value(lhs.as_i32() >> shift_count);
-    }
-
     // 13.15.3 ApplyStringOrNumericBinaryOperator ( lval, opText, rval ), https://tc39.es/ecma262/#sec-applystringornumericbinaryoperator
     // 1-2, 6. N/A.
 
@@ -1655,12 +1649,6 @@ ThrowCompletionOr<Value> right_shift(VM& vm, Value lhs, Value rhs)
 // ShiftExpression : ShiftExpression >>> AdditiveExpression
 ThrowCompletionOr<Value> unsigned_right_shift(VM& vm, Value lhs, Value rhs)
 {
-    // OPTIMIZATION: Fast path when both values are suitable Int32 values.
-    if (lhs.is_int32() && rhs.is_int32() && lhs.as_i32() >= 0 && rhs.as_i32() >= 0) {
-        auto shift_count = static_cast<u32>(rhs.as_i32()) % 32;
-        return Value(static_cast<u32>(lhs.as_i32()) >> shift_count);
-    }
-
     // 13.15.3 ApplyStringOrNumericBinaryOperator ( lval, opText, rval ), https://tc39.es/ecma262/#sec-applystringornumericbinaryoperator
     // 1-2, 5-6. N/A.