[GlobalOpt] Check stored once value's type before setting global initializer

[aeubanks]

Summary

In the provided test case, we were trying to set the global's
initializer to i32* null when the global's value type was @0.

[aeubanks]

seems to be caused by D106589

[aeubanks]

update

[rnk]

lgtm

llvm/lib/Transforms/IPO/GlobalOpt.cpp

if (SRAGlobal(GV, DL))
       return true;
   }
   if (GS.StoredType == GlobalStatus::StoredOnce && GS.StoredOnceValue) {
     // If the initial value for the global was an undef value, and if only
     // one other value was stored into it, we can just change the
     // initializer to be the stored value, then delete all stores to the
     // global.  This allows us to mark it constant.
     if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
-      if (isa<UndefValue>(GV->getInitializer())) {
+      if (SOVConstant->getType() == GV->getValueType() &&
+          isa<UndefValue>(GV->getInitializer())) {
         // Change the initial value here.
         GV->setInitializer(SOVConstant);
 
         // Clean up any obviously simplifiable users now.
         CleanupConstantGlobalUsers(GV, GV->getInitializer(), DL, GetTLI);
 
         if (GV->use_empty()) {
           LLVM_DEBUG(dbgs() << "   *** Substituting initializer allowed us to "

llvm/test/Transforms/GlobalOpt/stored-once-value-type.ll

+; RUN: opt -passes=globalopt < %s -S | FileCheck %s
+
+; Check that we don't try to set a global initializer to a value of a different type.
+; In this case, we were trying to set @0's initializer to be i32* null.
+
+%0 = type { i32* }
+
+@0 = internal global %0* null
+; CHECK: global %0 undef
+
+define void @a() {
+  %1 = tail call i8* @_Znwm(i64 8)
+  %2 = bitcast i8* %1 to %0*
+  %3 = getelementptr inbounds %0, %0* %2, i64 0, i32 0
+  store i32* null, i32** %3, align 8
+  store i8* %1, i8** bitcast (%0** @0 to i8**), align 8
+  %4 = load i64*, i64** bitcast (%0** @0 to i64**), align 8
+  %5 = load atomic i64, i64* %4 acquire, align 8
+  ret void
+}
+
+declare i8* @_Znwm(i64)