LibJS: Improve correctness of rounding and bitwise operations

Patch from Anonymous

Userland/Libraries/LibJS/Tests/operators/binary-bitwise-and.js

@@ -40,6 +40,9 @@ test("basic numeric and", () => {
     expect(5 & 3).toBe(1);
     expect(5 & 4).toBe(4);
     expect(5 & 5).toBe(5);
+
+    expect(0xffffffff & 0).toBe(0);
+    expect(0xffffffff & 0xffffffff).toBe(-1);
 });
 
 test("and with non-numeric values", () => {

Userland/Libraries/LibJS/Tests/operators/binary-bitwise-left-shift.js

@@ -40,6 +40,11 @@ test("basic numeric shifting", () => {
     expect(5 << 3).toBe(40);
     expect(5 << 4).toBe(80);
     expect(5 << 5).toBe(160);
+
+    expect(0xffffffff << 0).toBe(-1);
+    expect(0xffffffff << 16).toBe(-65536);
+    expect(0xffff0000 << 16).toBe(0);
+    expect(0xffff0000 << 15).toBe(-2147483648);
 });
 
 test("shifting with non-numeric values", () => {

Userland/Libraries/LibJS/Tests/operators/binary-bitwise-or.js

@@ -40,6 +40,10 @@ test("basic numeric or", () => {
     expect(5 | 3).toBe(7);
     expect(5 | 4).toBe(5);
     expect(5 | 5).toBe(5);
+
+    expect(0xffffffff | 0).toBe(-1);
+    expect(0xffffffff | 0xffffffff).toBe(-1);
+    expect(2147483648 | 0).toBe(-2147483648);
 });
 
 test("or with non-numeric values", () => {

Userland/Libraries/LibJS/Tests/operators/binary-bitwise-right-shift.js

@@ -26,6 +26,10 @@ test("basic numeric shifting", () => {
     expect(42 >> 3).toBe(5);
     expect(42 >> 4).toBe(2);
     expect(42 >> 5).toBe(1);
+
+    expect(0xffffffff >> 0).toBe(-1);
+    expect(0xffffffff >> 16).toBe(-1);
+    expect((0xf0000000 * 2) >> 16).toBe(-8192);
 });
 
 test("numeric shifting with negative lhs values", () => {

Userland/Libraries/LibJS/Tests/operators/binary-bitwise-unsigned-right-shift.js

@@ -26,6 +26,10 @@ test("basic numeric shifting", () => {
     expect(42 >>> 3).toBe(5);
     expect(42 >>> 4).toBe(2);
     expect(42 >>> 5).toBe(1);
+
+    expect(0xffffffff >>> 0).toBe(4294967295);
+    expect(0xffffffff >>> 16).toBe(65535);
+    expect((0xf0000000 * 2) >>> 16).toBe(57344);
 });
 
 test("numeric shifting with negative lhs values", () => {

Userland/Libraries/LibJS/Tests/operators/binary-bitwise-xor.js

@@ -40,6 +40,9 @@ test("basic numeric xor", () => {
     expect(5 ^ 3).toBe(6);
     expect(5 ^ 4).toBe(1);
     expect(5 ^ 5).toBe(0);
+
+    expect(0xffffffff ^ 0).toBe(-1);
+    expect(0xffffffff ^ 0xffffffff).toBe(0);
 });
 
 test("xor with non-numeric values", () => {