[BasicAA] Fix handling of invariant group launders

Summary:
A recent patch ([[ https://reviews.llvm.org/rL331587 | rL331587 ]]) to Capture Tracking taught it that the `launder_invariant_group` intrinsic captures its argument only by returning it. Unfortunately, BasicAA still considered every call instruction as a possible escape source and hence concluded that the result of a `launder_invariant_group` call cannot alias any local non-escaping value. This led to [[ https://bugs.llvm.org/show_bug.cgi?id=37458 | bug 37458 ]].

This patch updates the relevant check for escape sources in BasicAA.

Reviewers: Prazek, kuhar, rsmith, hfinkel, sanjoy, xbolva00

Reviewed By: hfinkel, xbolva00

Subscribers: JDevlieghere, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D46900

llvm-svn: 332466

2 files changed, 14 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index aaa79bc0199..55a53f2122a 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -132,7 +132,18 @@ static bool isNonEscapingLocalObject(const Value *V) {
 /// Returns true if the pointer is one which would have been considered an
 /// escape by isNonEscapingLocalObject.
 static bool isEscapeSource(const Value *V) {
-  if (isa<CallInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V))
+  if (auto CS = ImmutableCallSite(V)) {
+    // launder_invariant_group captures its argument only by returning it,
+    // so it might not be considered an escape by isNonEscapingLocalObject.
+    // Note that adding similar special cases for intrinsics in CaptureTracking
+    // requires handling them here too.
+    if (CS.getIntrinsicID() == Intrinsic::launder_invariant_group)
+      return false;
+
+    return true;
+  }
+
+  if (isa<Argument>(V))
     return true;
 
   // The load case works because isNonEscapingLocalObject considers all
diff --git a/llvm/lib/Analysis/CaptureTracking.cpp b/llvm/lib/Analysis/CaptureTracking.cpp
index 782e277222f..54466cd3467 100644
--- a/llvm/lib/Analysis/CaptureTracking.cpp
+++ b/llvm/lib/Analysis/CaptureTracking.cpp
@@ -249,6 +249,8 @@ void llvm::PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker) {
 
       // launder.invariant.group only captures pointer by returning it,
       // so the pointer wasn't captured if returned pointer is not captured.
+      // Note that adding similar special cases for intrinsics requires handling
+      // them in 'isEscapeSource' in BasicAA.
       if (CS.getIntrinsicID() == Intrinsic::launder_invariant_group) {
         AddUses(I);
         break;