IRGen: remove a wrong assert for global variable initialization

The assert was wrong because in case a global variable reference another global variable, it can be the case that the other variable is first generated as declaration and then "converted" to a definition by adding the constant initializer.

rdar://117189962

Author: eeckstein

lib/IRGen/GenDecl.cpp

@@ -2757,11 +2757,6 @@ Address IRGenModule::getAddrOfSILGlobalVariable(SILGlobalVariable *var,
   if (gvar) {
     if (forDefinition) {
       updateLinkageForDefinition(*this, gvar, entity);
-
-      if (var->getStaticInitializerValue()) {
-        assert(gvar->hasInitializer() &&
-               "global variable referenced before created");
-      }
     }
     if (forDefinition && !gvar->hasInitializer())
       initVal = getGlobalInitValue(var, storageType, fixedAlignment);

test/IRGen/referenced_global.swift

@@ -0,0 +1,9 @@
+// RUN: %target-swift-frontend -parse-as-library -primary-file %s -O -emit-ir -o - | %FileCheck %s
+
+// REQUIRES: swift_in_compiler
+
+// Check that IRGen doesn't crash when a global variable reference another private global.
+
+// CHECK-LABEL: @"$s17referenced_global1bSPySiGvp" ={{.*}} global {{.*}} ptr @"$s17referenced_global1x{{.*}}"
+public var b = UnsafePointer(&x)
+private var x = 1