Optimize comparison with zero and null

compiler/testData/codegen/bytecodeText/boxingOptimization/nullCheck.kt

@@ -13,5 +13,6 @@ fun bar() {
 
 // 0 valueOf
 // 0 Value\s\(\)
-// 1 IFNULL
-// 0 IFNONNULL
+// 0 IFNULL
+// 1 IFNONNULL
+// 1 IF

compiler/testData/codegen/bytecodeText/conditions/negatedNullCompare.kt

@@ -0,0 +1,14 @@
+fun main(p: String?) {
+    if (!(p == null)) {
+        "then"
+    } else {
+        "else"
+    }
+}
+
+//0 ICONST_0
+//0 ICONST_1
+//0 ACONST_NULL
+//1 IFNULL
+//1 IF
+//1 GOTO

compiler/testData/codegen/bytecodeText/conditions/negatedZeroCompare.kt

@@ -0,0 +1,15 @@
+fun main() {
+    val a = 1
+    if (!(a == 0)) {
+        "then"
+    } else {
+        "else"
+    }
+}
+
+//0 ICONST_0
+//1 ICONST_1
+//1 IFEQ
+//0 IFNE
+//1 IF
+//1 GOTO

compiler/testData/codegen/bytecodeText/conditions/nullCompare.kt

@@ -0,0 +1,14 @@
+fun main(p: String?) {
+    if (p == null) {
+        "then"
+    } else {
+        "else"
+    }
+}
+
+//0 ICONST_0
+//0 ICONST_1
+//0 ACONST_NULL
+//1 IFNONNULL
+//1 IF
+//1 GOTO

compiler/testData/codegen/bytecodeText/conditions/zeroCompare.kt

@@ -0,0 +1,15 @@
+fun main() {
+    val a = 1
+    if (a == 0) {
+        "then"
+    } else {
+        "else"
+    }
+}
+
+//0 ICONST_0
+//1 ICONST_1
+//0 IFEQ
+//1 IFNE
+//1 IF
+//1 GOTO