[llvm] [CGP] Undo constant propagation of pointers across calls (PR #102926)

[Yingwei Zheng via llvm-commits]

================
@@ -2686,6 +2686,47 @@ bool CodeGenPrepare::optimizeCallInst(CallInst *CI, ModifyDT &ModifiedDT) {
     return true;
   }
 
+  // SCCP may have propagated C++ static variables across calls. If this happens
+  // to be the case, we may want to undo it in order to avoid redundant pointer
+  // computation of the constant, as the function method returning the constant
+  // needs to be executed anyways.
+  auto GetUniformReturnValue = [](const Function *F) -> Constant * {
+    if (!F->getReturnType()->isPointerTy())
+      return nullptr;
+
+    Constant *UniformValue = nullptr;
+    for (auto &BB : llvm::reverse(*F)) {
+      if (auto *RI = dyn_cast<ReturnInst>(BB.getTerminator())) {
+        if (auto *V = dyn_cast_or_null<GlobalVariable>(RI->getReturnValue())) {
----------------
dtcxzyw wrote:

```suggestion
        if (auto *V = dyn_cast<GlobalVariable>(RI->getReturnValue())) {
```


https://github.com/llvm/llvm-project/pull/102926