Recommit "[LAA] Initial support for runtime checks with pointer selects."

This reverts commit 7aa8a678826dea86ff3e6c7df9d2a8a6ef868f5d.

This version includes fixes to address issues uncovered after
the commit landed and discussed at D11448.

Those include:

* Limit select-traversal to selects inside the loop.
* Freeze pointers resulting from looking through selects to avoid
  branch-on-poison.

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 965b35a..1310abb 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -1525,6 +1525,11 @@ static PointerBounds expandBounds(const RuntimeCheckingPtrGroup *CG,
   LLVM_DEBUG(dbgs() << "LAA: Adding RT check for range:\n");
   Start = Exp.expandCodeFor(CG->Low, PtrArithTy, Loc);
   End = Exp.expandCodeFor(CG->High, PtrArithTy, Loc);
+  if (CG->NeedsFreeze) {
+    IRBuilder<> Builder(Loc);
+    Start = Builder.CreateFreeze(Start, Start->getName() + ".fr");
+    End = Builder.CreateFreeze(End, End->getName() + ".fr");
+  }
   LLVM_DEBUG(dbgs() << "Start: " << *CG->Low << " End: " << *CG->High << "\n");
   return {Start, End};
 }
@@ -1623,6 +1628,11 @@ Value *llvm::addDiffRuntimeChecks(
                              ConstantInt::get(Ty, IC * C.AccessSize));
     Value *Sink = Expander.expandCodeFor(C.SinkStart, Ty, Loc);
     Value *Src = Expander.expandCodeFor(C.SrcStart, Ty, Loc);
+    if (C.NeedsFreeze) {
+      IRBuilder<> Builder(Loc);
+      Sink = Builder.CreateFreeze(Sink, Sink->getName() + ".fr");
+      Src = Builder.CreateFreeze(Src, Src->getName() + ".fr");
+    }
     Value *Diff = ChkBuilder.CreateSub(Sink, Src);
     Value *IsConflict =
         ChkBuilder.CreateICmpULT(Diff, VFTimesUFTimesSize, "diff.check");