[clang][bytecode] Fix a crash in codegen (llvm#151515)

getRecord() can return nullptr if any one of the fields does, in this
case because the array is too large for us to allocate.

Author: tbaederr

clang/lib/AST/ByteCode/Compiler.cpp

@@ -1758,6 +1758,9 @@ bool Compiler<Emitter>::visitInitList(ArrayRef<const Expr *> Inits,
     if (Inits.size() == 1 && E->getType() == Inits[0]->getType())
       return this->delegate(Inits[0]);
 
+    if (!R)
+      return false;
+
     auto initPrimitiveField = [=](const Record::Field *FieldToInit,
                                   const Expr *Init, PrimType T,
                                   bool Activate = false) -> bool {

clang/test/AST/ByteCode/codegen.cpp

@@ -23,6 +23,10 @@ S s;
 // CHECK: @sp = constant ptr getelementptr (i8, ptr @s, i64 16), align 8
 float &sp = s.c[3];
 
+namespace NearlyZeroInit {
+  // CHECK: @_ZN14NearlyZeroInit1bE ={{.*}} global{{.*}} { i32, <{ i32, [2147483647 x i32] }> } { i32 1, <{ i32, [2147483647 x i32] }> <{ i32 2, [2147483647 x i32] zeroinitializer }> }{{.*}}
+  struct B { int n; int arr[1024 * 1024 * 1024 * 2u]; } b = {1, {2}};
+}
 
 namespace BaseClassOffsets {
   struct A { int a; };