[PATCH] D97978: [llvm] Change DSOLocalEquivalent type if the underlying global value type changes

[Leonard Chan via Phabricator via llvm-commits]

leonardchan created this revision.
leonardchan added reviewers: phosek, mcgrathr.
Herald added subscribers: dexonsmith, hiraditya.
leonardchan requested review of this revision.
Herald added a project: LLVM.

We encountered an issue where LTO running on IR that used the `DSOLocalEquivalent` constant would result in bad codegen. The underlying issue was that a DSOLocalEquivalent could have a different type from the underlying GV it's referencing when it should always have the same type as its GV. This updates `DSOLocalEquivalent::handleOperandChangeImpl` to change the type if the GV type changes.

This also caught an issue where the `ValueMapper` wasn't properly handling  `DSOLocalEquivalent`, so this just adds the machinery for handling it. This part is mostly mechanical.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D97978

Files:
  llvm/lib/IR/Constants.cpp
  llvm/lib/Transforms/Utils/ValueMapper.cpp


Index: llvm/lib/Transforms/Utils/ValueMapper.cpp
===================================================================
--- llvm/lib/Transforms/Utils/ValueMapper.cpp
+++ llvm/lib/Transforms/Utils/ValueMapper.cpp
@@ -412,6 +412,20 @@
   if (BlockAddress *BA = dyn_cast<BlockAddress>(C))
     return mapBlockAddress(*BA);
 
+  if (const auto *Equiv = dyn_cast<DSOLocalEquivalent>(C)) {
+    auto *Val = mapValue(Equiv->getGlobalValue());
+    GlobalValue *GV = dyn_cast<GlobalValue>(Val);
+    if (GV)
+      return getVM()[Equiv] = DSOLocalEquivalent::get(GV);
+
+    auto *Func = cast<Function>(Val->stripPointerCastsAndAliases());
+    Type *NewTy = Equiv->getType();
+    if (TypeMapper)
+      NewTy = TypeMapper->remapType(NewTy);
+    return getVM()[Equiv] = llvm::ConstantExpr::getBitCast(
+               DSOLocalEquivalent::get(Func), NewTy);
+  }
+
   auto mapValueOrNull = [this](Value *V) {
     auto Mapped = mapValue(V);
     assert((Mapped || (Flags & RF_NullMapMissingGlobalValues)) &&
Index: llvm/lib/IR/Constants.cpp
===================================================================
--- llvm/lib/IR/Constants.cpp
+++ llvm/lib/IR/Constants.cpp
@@ -1908,6 +1908,12 @@
   getContext().pImpl->DSOLocalEquivalents.erase(getGlobalValue());
   NewEquiv = this;
   setOperand(0, Func);
+
+  if (Func->getType() != getType()) {
+    // It is ok to mutate the type here because this constant should always
+    // reflect the type of the function it's holding.
+    mutateType(Func->getType());
+  }
   return nullptr;
 }
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D97978.328297.patch
Type: text/x-patch
Size: 1530 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20210304/2ac081a4/attachment.bin>