1 files changed, 9 insertions, 7 deletions
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 0167751..883462a 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -431,13 +431,15 @@ bool BasicAAResult::DecomposeGEPExpression(const Value *V,
     const GEPOperator *GEPOp = dyn_cast<GEPOperator>(Op);
     if (!GEPOp) {
       if (auto CS = ImmutableCallSite(V)) {
-        // Note: getArgumentAliasingToReturnedPointer keeps it in sync with
-        // CaptureTracking, which is needed for correctness.  This is because
-        // some intrinsics like launder.invariant.group returns pointers that
-        // are aliasing it's argument, which is known to CaptureTracking.
-        // If AliasAnalysis does not use the same information, it could assume
-        // that pointer returned from launder does not alias it's argument
-        // because launder could not return it if the pointer was not captured.
+        // CaptureTracking can know about special capturing properties of some
+        // intrinsics like launder.invariant.group, that can't be expressed with
+        // the attributes, but have properties like returning aliasing pointer.
+        // Because some analysis may assume that nocaptured pointer is not
+        // returned from some special intrinsic (because function would have to
+        // be marked with returns attribute), it is crucial to use this function
+        // because it should be in sync with CaptureTracking. Not using it may
+        // cause weird miscompilations where 2 aliasing pointers are assumed to
+        // noalias.
         if (auto *RP = getArgumentAliasingToReturnedPointer(CS)) {
           V = RP;
           continue;