Copy noalias metadata from call sites to inlined instructions

When a call site with noalias metadata is inlined, that metadata can be
propagated directly to the inlined instructions (only those that might access
memory because it is not useful on the others). Prior to inlining, the noalias
metadata could express that a call would not alias with some other memory
access, which implies that no instruction within that called function would
alias. By propagating the metadata to the inlined instructions, we preserve
that knowledge.

This should complete the enhancements requested in PR20500.

llvm-svn: 215676

1 files changed, 28 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index f6289b5c891..a3535cb47cc 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -356,11 +356,35 @@ static void CloneAliasScopeMetadata(CallSite CS, ValueToValueMapTy &VMap) {
     if (!NI)
       continue;
 
-    if (MDNode *M = NI->getMetadata(LLVMContext::MD_alias_scope))
-      NI->setMetadata(LLVMContext::MD_alias_scope, MDMap[M]);
+    if (MDNode *M = NI->getMetadata(LLVMContext::MD_alias_scope)) {
+      MDNode *NewMD = MDMap[M];
+      // If the call site also had alias scope metadata (a list of scopes to
+      // which instructions inside it might belong), propagate those scopes to
+      // the inlined instructions.
+      if (MDNode *CSM =
+          CS.getInstruction()->getMetadata(LLVMContext::MD_alias_scope))
+        NewMD = MDNode::concatenate(NewMD, CSM);
+      NI->setMetadata(LLVMContext::MD_alias_scope, NewMD);
+    } else if (NI->mayReadOrWriteMemory()) {
+      if (MDNode *M =
+          CS.getInstruction()->getMetadata(LLVMContext::MD_alias_scope))
+        NI->setMetadata(LLVMContext::MD_alias_scope, M);
+    }
 
-    if (MDNode *M = NI->getMetadata(LLVMContext::MD_noalias))
-      NI->setMetadata(LLVMContext::MD_noalias, MDMap[M]);
+    if (MDNode *M = NI->getMetadata(LLVMContext::MD_noalias)) {
+      MDNode *NewMD = MDMap[M];
+      // If the call site also had noalias metadata (a list of scopes with
+      // which instructions inside it don't alias), propagate those scopes to
+      // the inlined instructions.
+      if (MDNode *CSM =
+          CS.getInstruction()->getMetadata(LLVMContext::MD_noalias))
+        NewMD = MDNode::concatenate(NewMD, CSM);
+      NI->setMetadata(LLVMContext::MD_noalias, NewMD);
+    } else if (NI->mayReadOrWriteMemory()) {
+      if (MDNode *M =
+          CS.getInstruction()->getMetadata(LLVMContext::MD_noalias))
+        NI->setMetadata(LLVMContext::MD_noalias, M);
+    }
   }
 
   // Now that everything has been replaced, delete the dummy nodes.