[llvm] [PPCMergeStringPool] Avoid replacing constant with instruction (PR #88846)

[Chen Zheng via llvm-commits]

================
@@ -330,38 +338,13 @@ void PPCMergeStringPool::replaceUsesWithGEP(GlobalVariable *GlobalToReplace,
     if (isa<GlobalValue>(CurrentUser))
       continue;
 
-    if (!UserInstruction) {
-      // User is a constant type.
-      Constant *ConstGEP = ConstantExpr::getInBoundsGetElementPtr(
-          PooledStructType, GPool, Indices);
-      UserConstant->handleOperandChange(GlobalToReplace, ConstGEP);
-      continue;
-    }
-
-    if (PHINode *UserPHI = dyn_cast<PHINode>(UserInstruction)) {
-      // GEP instructions cannot be added before PHI nodes.
-      // With getInBoundsGetElementPtr we create the GEP and then replace it
-      // inline into the PHI.
-      Constant *ConstGEP = ConstantExpr::getInBoundsGetElementPtr(
-          PooledStructType, GPool, Indices);
-      UserPHI->replaceUsesOfWith(GlobalToReplace, ConstGEP);
-      continue;
-    }
-    // The user is a valid instruction that is not a PHINode.
-    GetElementPtrInst *GEPInst =
-        GetElementPtrInst::Create(PooledStructType, GPool, Indices);
-    GEPInst->insertBefore(UserInstruction);
-
-    LLVM_DEBUG(dbgs() << "Inserting GEP before:\n");
-    LLVM_DEBUG(UserInstruction->dump());
-
+    Constant *ConstGEP = ConstantExpr::getInBoundsGetElementPtr(
+        PooledStructType, GPool, Indices);
----------------
chenzheng1030 wrote:

Now the two variables `UserConstant` and `UserInstruction` will cause unused variables warning on assertion-off build? Maybe we can just use `isa<>` inside the assert at line 330?

https://github.com/llvm/llvm-project/pull/88846