Allow isDereferenceablePointer to look through some bitcasts

isDereferenceablePointer should not give up upon encountering any bitcast. If
we're casting from a pointer to a larger type to a pointer to a small type, we
can continue by examining the bitcast's operand. This missing capability
was noted in a comment in the function.

In order for this to work, isDereferenceablePointer now takes an optional
DataLayout pointer (essentially all callers already had such a pointer
available). Most code uses isDereferenceablePointer though
isSafeToSpeculativelyExecute (which already took an optional DataLayout
pointer), and to enable the LICM test case, LICM needs to actually provide its DL
pointer to isSafeToSpeculativelyExecute (which it was not doing previously).

llvm-svn: 212686

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index e664454..5264745 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2007,7 +2007,7 @@ bool llvm::isSafeToSpeculativelyExecute(const Value *V,
         // Speculative load may create a race that did not exist in the source.
         LI->getParent()->getParent()->hasFnAttribute(Attribute::SanitizeThread))
       return false;
-    return LI->getPointerOperand()->isDereferenceablePointer();
+    return LI->getPointerOperand()->isDereferenceablePointer(TD);
   }
   case Instruction::Call: {
    if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {