[StructuralHash] Track global variables

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D149209

llvm/lib/IR/StructuralHash.cpp

@@ -8,6 +8,7 @@
 
 #include "llvm/IR/StructuralHash.h"
 #include "llvm/IR/Function.h"
+#include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/Module.h"
 
 using namespace llvm;
@@ -27,9 +28,12 @@ public:
   StructuralHashImpl() : Hash(4) {}
 
   void update(const Function &F) {
-    if (F.empty())
+    // Declarations don't affect analyses.
+    if (F.isDeclaration())
       return;
 
+    hash(12345); // Function header
+
     hash(F.isVarArg());
     hash(F.arg_size());
 
@@ -53,7 +57,17 @@ public:
     }
   }
 
+  void update(const GlobalVariable &GV) {
+    // used/compiler.used don't affect analyses.
+    if (GV.getName() == "llvm.compiler.used" || GV.getName() == "llvm.used")
+      return;
+    hash(23456); // Global header
+    hash(GV.getValueType()->getTypeID());
+  }
+
   void update(const Module &M) {
+    for (const GlobalVariable &GV : M.globals())
+      update(GV);
     for (const Function &F : M)
       update(F);
   }