[CallSite] Make construction from Value* (or Instruction*) explicit.

CallSite roughly behaves as a common base CallInst and InvokeInst. Bring
the behavior closer to that model by making upcasts explicit. Downcasts
remain implicit and work as before.

Following dyn_cast as a mental model checking whether a Value *V isa
CallSite now looks like this: 
  if (auto CS = CallSite(V)) // think dyn_cast
instead of:
  if (CallSite CS = V)

This is an extra token but I think it is slightly clearer. Making the
ctor explicit has the advantage of not accidentally creating nullptr
CallSites, e.g. when you pass a Value * to a function taking a CallSite
argument.

llvm-svn: 234601

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index 78bfca40916..f6eb4273a53 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -525,7 +525,7 @@ static bool isDereferenceablePointer(const Value *V, const DataLayout &DL,
 
   // Return values from call sites specifically marked as dereferenceable are
   // also okay.
-  if (ImmutableCallSite CS = V) {
+  if (auto CS = ImmutableCallSite(V)) {
     if (uint64_t Bytes = CS.getDereferenceableBytes(0)) {
       Type *Ty = V->getType()->getPointerElementType();
       if (Ty->isSized() && DL.getTypeStoreSize(Ty) <= Bytes)
@@ -595,7 +595,7 @@ bool Value::isDereferenceablePointer(const DataLayout &DL) const {
     APInt DerefBytes(Offset.getBitWidth(), 0);
     if (const Argument *A = dyn_cast<Argument>(BV))
       DerefBytes = A->getDereferenceableBytes();
-    else if (ImmutableCallSite CS = BV)
+    else if (auto CS = ImmutableCallSite(BV))
       DerefBytes = CS.getDereferenceableBytes(0);
 
     if (DerefBytes.getBoolValue() && Offset.isNonNegative()) {