[Inline] Fix noalias addition on simplified instructions (PR50589)

When adding noalias/alias.scope metadata, we analyze the instructions
of the original callee, and then place metadata on the corresponding
inlined instructions in the caller as provided by VMap. However, this
assumes that this actually a clone of the instruction, rather than
the result of simplification. If simplification occurred, the
instruction that VMap points to may not have any relationship as far
as ModRef behavior is concerned.

Fix this by tracking simplified instructions during cloning and then
only processing instructions that have not been simplified. This is
done with an additional map form original to cloned instruction,
into which we only insert if no simplification is performed. The
mapping in VMap can then be compared to this map. If they're the
same, the instruction hasn't been simplified. (I originally wanted
to only track a set of simplified instructions, but that wouldn't
work if the instruction only gets simplified afterwards, e.g. based
on rewritten phis.)

Fixes https://bugs.llvm.org/show_bug.cgi?id=50589.

Differential Revision: https://reviews.llvm.org/D106242

Author: nikic

llvm/include/llvm/Transforms/Utils/Cloning.h

@@ -75,7 +75,16 @@ struct ClonedCodeInfo {
   /// originally inserted callsites were DCE'ed after they were cloned.
   std::vector<WeakTrackingVH> OperandBundleCallSites;
 
+  /// Like VMap, but maps only unsimplified instructions. Values in the map
+  /// may be dangling, it is only intended to be used via isSimplified(), to
+  /// check whether the main VMap mapping involves simplification or not.
+  DenseMap<const Value *, const Value *> OrigVMap;
+
   ClonedCodeInfo() = default;
+
+  bool isSimplified(const Value *From, const Value *To) const {
+    return OrigVMap.lookup(From) != To;
+  }
 };
 
 /// Return a copy of the specified basic block, but without

llvm/lib/Transforms/Utils/CloneFunction.cpp

@@ -412,10 +412,12 @@ void PruningFunctionCloner::CloneBlock(
     NewBB->getInstList().push_back(NewInst);
     hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
 
-    if (CodeInfo)
+    if (CodeInfo) {
+      CodeInfo->OrigVMap[&*II] = NewInst;
       if (auto *CB = dyn_cast<CallBase>(&*II))
         if (CB->hasOperandBundles())
           CodeInfo->OperandBundleCallSites.push_back(NewInst);
+    }
 
     if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
       if (isa<ConstantInt>(AI->getArraySize()))
@@ -469,10 +471,12 @@ void PruningFunctionCloner::CloneBlock(
     NewBB->getInstList().push_back(NewInst);
     VMap[OldTI] = NewInst; // Add instruction map to value.
 
-    if (CodeInfo)
+    if (CodeInfo) {
+      CodeInfo->OrigVMap[OldTI] = NewInst;
       if (auto *CB = dyn_cast<CallBase>(OldTI))
         if (CB->hasOperandBundles())
           CodeInfo->OperandBundleCallSites.push_back(NewInst);
+    }
 
     // Recursively clone any reachable successor blocks.
     append_range(ToClone, successors(BB->getTerminator()));

llvm/lib/Transforms/Utils/InlineFunction.cpp

@@ -939,7 +939,8 @@ void ScopedAliasMetadataDeepCloner::remap(Function::iterator FStart,
 /// parameters with noalias metadata specifying the new scope, and tag all
 /// non-derived loads, stores and memory intrinsics with the new alias scopes.
 static void AddAliasScopeMetadata(CallBase &CB, ValueToValueMapTy &VMap,
-                                  const DataLayout &DL, AAResults *CalleeAAR) {
+                                  const DataLayout &DL, AAResults *CalleeAAR,
+                                  ClonedCodeInfo &InlinedFunctionInfo) {
   if (!EnableNoAliasConversion)
     return;
 
@@ -1009,7 +1010,7 @@ static void AddAliasScopeMetadata(CallBase &CB, ValueToValueMapTy &VMap,
         continue;
 
       Instruction *NI = dyn_cast<Instruction>(VMI->second);
-      if (!NI)
+      if (!NI || InlinedFunctionInfo.isSimplified(I, NI))
         continue;
 
       bool IsArgMemOnlyCall = false, IsFuncCall = false;
@@ -2037,7 +2038,7 @@ llvm::InlineResult llvm::InlineFunction(CallBase &CB, InlineFunctionInfo &IFI,
     SAMetadataCloner.remap(FirstNewBlock, Caller->end());
 
     // Add noalias metadata if necessary.
-    AddAliasScopeMetadata(CB, VMap, DL, CalleeAAR);
+    AddAliasScopeMetadata(CB, VMap, DL, CalleeAAR, InlinedFunctionInfo);
 
     // Clone return attributes on the callsite into the calls within the inlined
     // function which feed into its return value.

llvm/test/Transforms/Inline/pr50589.ll

@@ -15,10 +15,10 @@ define <2 x i8> @callee1(<2 x i8>* %ptr1, <2 x i8>* noalias %ptr2, <2 x i1> %mas
   ret <2 x i8> %ret
 }
 
-; TODO: The load should not have !noalias.
+; The load should not have !noalias.
 define void @caller1(<2 x i8>* %ptr1, <2 x i8>* %ptr2) {
 ; CHECK-LABEL: @caller1(
-; CHECK-NEXT:    [[PASSTHRU:%.*]] = load <2 x i8>, <2 x i8>* [[PTR2:%.*]], align 2, !noalias !0
+; CHECK-NEXT:    [[PASSTHRU:%.*]] = load <2 x i8>, <2 x i8>* [[PTR2:%.*]], align 2{{$}}
 ; CHECK-NEXT:    call void @llvm.experimental.noalias.scope.decl(metadata [[META0:![0-9]+]])
 ; CHECK-NEXT:    store <2 x i8> zeroinitializer, <2 x i8>* [[PTR2]], align 2, !alias.scope !0
 ; CHECK-NEXT:    ret void
@@ -41,11 +41,11 @@ define <2 x i8> @callee2(<2 x i8>* %ptr1, <2 x i8>* noalias %ptr2, <2 x i1> %mas
   ret <2 x i8> %ret
 }
 
-; TODO: The load should not have !noalias.
+; The load should not have !noalias.
 define void @caller2(<2 x i8>* %ptr1, <2 x i8>* %ptr2) {
 ; CHECK-LABEL: @caller2(
 ; CHECK-NEXT:    call void @llvm.experimental.noalias.scope.decl(metadata [[META3:![0-9]+]])
-; CHECK-NEXT:    [[PASSTHRU_I:%.*]] = load <2 x i8>, <2 x i8>* [[PTR2:%.*]], align 2, !alias.scope !3, !noalias !3
+; CHECK-NEXT:    [[PASSTHRU_I:%.*]] = load <2 x i8>, <2 x i8>* [[PTR2:%.*]], align 2, !alias.scope !3{{$}}
 ; CHECK-NEXT:    store <2 x i8> zeroinitializer, <2 x i8>* [[PTR2]], align 2, !alias.scope !3
 ; CHECK-NEXT:    ret void
 ;