[StructuralHash] Ignore global variable declarations

[uabelho]

Summary

Ignore declarations of global variables, just as we do with declarations
of functions.

Done as a follow up to the comments in https://reviews.llvm.org/D149209.

[aeubanks]

llvm/test/Transforms/StripDeadPrototypes/remove-global-variable-declaration.ll

10

all you need is this global declaration in the test, nothing else below is necessary

[uabelho]

Simplified testcase

[uabelho]

llvm/test/Transforms/StripDeadPrototypes/remove-global-variable-declaration.ll

10

Thanks!

[aeubanks]

lg

llvm/lib/IR/StructuralHash.cpp

while (!BBs.empty()) {
         if (!VisitedBBs.insert(Term->getSuccessor(i)).second)
           continue;
         BBs.push_back(Term->getSuccessor(i));
       }
     }
   }
 
   void update(const GlobalVariable &GV) {
-    // used/compiler.used don't affect analyses.
+    // Declarations and used/compiler.used don't affect analyses.
     // Same for llvm.embedded.object, which is always a metadata section.
-    if (GV.getName() == "llvm.compiler.used" || GV.getName() == "llvm.used" ||
+    if (GV.isDeclaration() ||
+        GV.getName() == "llvm.compiler.used" || GV.getName() == "llvm.used" ||
         GV.getName() == "llvm.embedded.object")
       return;
     hash(23456); // Global header
     hash(GV.getValueType()->getTypeID());
   }
 
   void update(const Module &M) {
     for (const GlobalVariable &GV : M.globals())

llvm/test/Transforms/StripDeadPrototypes/remove-global-variable-declaration.ll

+; RUN: opt -passes=strip-dead-prototypes -S -verify-analysis-invalidation < %s | FileCheck %s
+
+; The declaration of the unused global variable @.str should be removed without
+; getting any error from -verify-analysis-invalidation.
+
+; CHECK-NOT: @.str
+
+@.str = external constant [15 x i16]
+