[turbofan] Add CHECKs to hunt down a crash

Bug: chromium:1027130
Change-Id: Ifd1f355ce266e672183f337f114432f11a866a52
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2011835
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65910}

src/codegen/string-constants.cc

@@ -22,6 +22,7 @@ Handle<String> StringConstantBase::AllocateStringConstant(
   switch (kind()) {
     case StringConstantKind::kStringLiteral: {
       result = static_cast<const StringLiteral*>(this)->str();
+      CHECK(!result.is_null());
       break;
     }
     case StringConstantKind::kNumberToStringConstant: {
@@ -29,6 +30,7 @@ Handle<String> StringConstantBase::AllocateStringConstant(
       Handle<Object> num_obj =
           isolate->factory()->NewNumber(num_constant->num());
       result = isolate->factory()->NumberToString(num_obj);
+      CHECK(!result.is_null());
       break;
     }
     case StringConstantKind::kStringCons: {

src/compiler/backend/code-generator.cc

@@ -894,6 +894,7 @@ Handle<DeoptimizationData> CodeGenerator::GenerateDeoptimizationData() {
       static_cast<int>(deoptimization_literals_.size()), AllocationType::kOld);
   for (unsigned i = 0; i < deoptimization_literals_.size(); i++) {
     Handle<Object> object = deoptimization_literals_[i].Reify(isolate());
+    CHECK(!object.is_null());
     literals->set(i, *object);
   }
   data->SetLiteralArray(*literals);

src/compiler/backend/code-generator.h

@@ -59,7 +59,7 @@ class DeoptimizationLiteral {
   DeoptimizationLiteral() : object_(), number_(0), string_(nullptr) {}
   explicit DeoptimizationLiteral(Handle<Object> object)
       : kind_(DeoptimizationLiteralKind::kObject), object_(object) {
-    DCHECK(!object_.is_null());
+    CHECK(!object_.is_null());
   }
   explicit DeoptimizationLiteral(double number)
       : kind_(DeoptimizationLiteralKind::kNumber), number_(number) {}