[AMDGPU] Limit promoting allocas that have users with dynamic index above a threshold on number of elements

llvm/lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp

@@ -85,6 +85,12 @@ static cl::opt<unsigned>
                             "when sorting profitable allocas"),
                    cl::init(4));
 
+static cl::opt<unsigned> PromoteAllocaDynamicIndexNumberElementLimit(
+    "amdgpu-promote-alloca-dynamic-index-num-element-limit",
+    cl::desc("Maximum number of elements for promoting alloca with dynamic"
+             " index"),
+    cl::init(8));
+
 // Shared implementation which can do both promotion to vector and to LDS.
 class AMDGPUPromoteAllocaImpl {
 private:
@@ -920,6 +926,23 @@ bool AMDGPUPromoteAllocaImpl::tryPromoteAllocaToVector(AllocaInst &Alloca) {
       if (!Index)
         return RejectUser(Inst, "cannot compute vector index for GEP");
 
+      auto Predicate = [&](const User *U) -> bool {
+        if (auto *LI = dyn_cast<LoadInst>(U)) {
+          if (auto *LoadVecTy = dyn_cast<FixedVectorType>(LI->getType())) {
+            if (LoadVecTy->getNumElements() >
+                PromoteAllocaDynamicIndexNumberElementLimit)
+              return true;
+          }
+        }
+        return false;
+      };
+      if (!isa<ConstantInt>(Index)) {
+        if (llvm::any_of(GEP->users(), Predicate)) {
+          return RejectUser(Inst,
+                            "user has too many elements for dynamic index");
+        }
+      }
+
       GEPVectorIdx[GEP] = Index;
       UsersToRemove.push_back(Inst);
       continue;