2 files changed, 13 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/MemoryBuiltins.cpp b/llvm/lib/Analysis/MemoryBuiltins.cpp
index 52f31238227..5acdeb64a40 100644
--- a/llvm/lib/Analysis/MemoryBuiltins.cpp
+++ b/llvm/lib/Analysis/MemoryBuiltins.cpp
@@ -307,6 +307,13 @@ bool llvm::isOpNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
   return getAllocationData(V, OpNewLike, TLI, LookThroughBitCast).hasValue();
 }
 
+/// Tests if a value is a call or invoke to a library function that
+/// allocates memory (strdup, strndup).
+bool llvm::isStrdupLikeFn(const Value *V, const TargetLibraryInfo *TLI,
+                          bool LookThroughBitCast) {
+  return getAllocationData(V, StrDupLike, TLI, LookThroughBitCast).hasValue();
+}
+
 /// extractMallocCall - Returns the corresponding CallInst if the instruction
 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
 /// ignore InvokeInst here.
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index e96e45e802a..90438189f89 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -4208,6 +4208,12 @@ static void annotateAnyAllocSite(CallBase &Call, const TargetLibraryInfo *TLI) {
       Call.addAttribute(AttributeList::ReturnIndex,
                         Attribute::getWithDereferenceableOrNullBytes(
                             Call.getContext(), Size.getZExtValue()));
+  } else if (isStrdupLikeFn(&Call, TLI) && Call.getNumArgOperands() == 1) {
+    // TODO: handle strndup
+    if (uint64_t Len = GetStringLength(Call.getOperand(0)))
+      Call.addAttribute(
+          AttributeList::ReturnIndex,
+          Attribute::getWithDereferenceableOrNullBytes(Call.getContext(), Len));
   }
 }