[ArgPromotion] Fix a truncated variable

[mstorsjo]

Summary

This fixes a regression since SVN rev 273808 (which was supposed to not change functionality).

The regression caused miscompilations (noted in the wild when targeting AArch64) on platforms with 32 bit long.

[rengolin]

Wouldn't it be better to set the type manually to something like uint32_t or uint64_t? To make sure they're the same across all arches?

[mstorsjo]

This fixes PR32917.

[mstorsjo]

In D32850#745797, @rengolin wrote:

Wouldn't it be better to set the type manually to something like uint32_t or uint64_t? To make sure they're the same across all arches?

That'd work as well. Although in this case, ArgIndex.second is a std::vector<uint64_t>, so auto here always means uint64_t, regardless of platform.

[rengolin]

Right, makes sense. This is an obvious fix, so I feel comfortable approving this one. LGTM. Thanks!

[sanjoy]

If I understand what happened, this is scary -- if clang-tidy introduces bugs like this perhaps we should think twice before checking in large mechanical changes like 273808?

Have you filed a bug for clang-tidy specifically?

llvm/trunk/lib/Transforms/IPO/ArgumentPromotion.cpp

for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
         std::vector<Value *> Ops;
         for (const auto &ArgIndex : ArgIndices) {
           Value *V = *AI;
           LoadInst *OrigLoad =
               OriginalLoads[std::make_pair(&*I, ArgIndex.second)];
           if (!ArgIndex.second.empty()) {
             Ops.reserve(ArgIndex.second.size());
             Type *ElTy = V->getType();
-            for (unsigned long II : ArgIndex.second) {
+            for (auto II : ArgIndex.second) {
               // Use i32 to index structs, and i64 for others (pointers/arrays).
               // This satisfies GEP constraints.
               Type *IdxTy =
                   (ElTy->isStructTy() ? Type::getInt32Ty(F->getContext())
                                       : Type::getInt64Ty(F->getContext()));
               Ops.push_back(ConstantInt::get(IdxTy, II));
               // Keep track of the type we're currently indexing.
               if (auto *ElPTy = dyn_cast<PointerType>(ElTy))