Implement strip.invariant.group
Summary:
This patch introduce new intrinsic -
strip.invariant.group that was described in the
RFC: Devirtualization v2
Reviewers: rsmith, hfinkel, nlopes, sanjoy, amharc, kuhar
Subscribers: arsenm, nhaehnle, JDevlieghere, hiraditya, xbolva00, llvm-commits
Differential Revision: https://reviews.llvm.org/D47103
Co-authored-by: Krzysztof Pszeniczny <krzysztof.pszeniczny@gmail.com>
llvm-svn: 336073
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 @@
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;