[cleanup] Replace 0 and NULL with nullptr for compiler files.

Fixing clang-tidy warning.

Bug: v8:8015
Change-Id: I20fd23b5370d15dddc913f6bdb05e649d71c2059
Reviewed-on: https://chromium-review.googlesource.com/1224373Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Florian Sattler <sattlerf@google.com>
Cr-Commit-Position: refs/heads/master@{#55919}

test/unittests/compiler/graph-reducer-unittest.cc

@@ -751,7 +751,7 @@ TEST_F(GraphReducerTest, Sorter1) {
     Node* n1 = graph()->NewNode(&kOpA0);
     Node* n2 = graph()->NewNode(&kOpA1, n1);
     Node* n3 = graph()->NewNode(&kOpA1, n1);
-    Node* end = NULL;  // Initialize to please the compiler.
+    Node* end = nullptr;  // Initialize to please the compiler.
 
     if (i == 0) end = graph()->NewNode(&kOpA2, n2, n3);
     if (i == 1) end = graph()->NewNode(&kOpA2, n3, n2);

test/unittests/compiler/node-cache-unittest.cc

@@ -63,7 +63,7 @@ TEST_F(NodeCacheTest, Int32Constant_hits) {
   for (int i = 0; i < kSize; i++) {
     int32_t v = i * -55;
     Node** pos = cache.Find(zone(), v);
-    if (*pos != NULL) {
+    if (*pos != nullptr) {
       EXPECT_EQ(nodes[i], *pos);
       hits++;
     }
@@ -101,7 +101,7 @@ TEST_F(NodeCacheTest, Int64Constant_hits) {
   for (int i = 0; i < kSize; i++) {
     int64_t v = static_cast<int64_t>(i) * static_cast<int64_t>(5003001);
     Node** pos = cache.Find(zone(), v);
-    if (*pos != NULL) {
+    if (*pos != nullptr) {
       EXPECT_EQ(nodes[i], *pos);
       hits++;
     }
@@ -118,7 +118,7 @@ TEST_F(NodeCacheTest, GetCachedNodes_int32) {
   for (size_t i = 0; i < arraysize(constants); i++) {
     int32_t k = constants[i];
     Node** pos = cache.Find(zone(), k);
-    if (*pos != NULL) {
+    if (*pos != nullptr) {
       ZoneVector<Node*> nodes(zone());
       cache.GetCachedNodes(&nodes);
       EXPECT_THAT(nodes, Contains(*pos));
@@ -141,7 +141,7 @@ TEST_F(NodeCacheTest, GetCachedNodes_int64) {
   for (size_t i = 0; i < arraysize(constants); i++) {
     int64_t k = constants[i];
     Node** pos = cache.Find(zone(), k);
-    if (*pos != NULL) {
+    if (*pos != nullptr) {
       ZoneVector<Node*> nodes(zone());
       cache.GetCachedNodes(&nodes);
       EXPECT_THAT(nodes, Contains(*pos));

test/unittests/compiler/node-test-utils.cc

@@ -57,7 +57,7 @@ class TestNodeMatcher : public MatcherInterface<Node*> {
 
   bool MatchAndExplain(Node* node,
                        MatchResultListener* listener) const override {
-    if (node == NULL) {
+    if (node == nullptr) {
       *listener << "which is NULL";
       return false;
     }