[SIL] Added SILBasicBlock::hasPhi.

Author: nate-chandler

include/swift/SIL/SILBasicBlock.h

@@ -426,6 +426,12 @@ public SwiftObjectHeader {
   /// the debug scope for newly created instructions.
   const SILDebugScope *getScopeOfFirstNonMetaInstruction();
 
+  /// Whether the block has any phi arguments.
+  ///
+  /// Note that a block could have an argument and still return false.  The
+  /// argument must also satisfy SILPhiArgument::isPhiArgument.
+  bool hasPhi() const;
+
   //===--------------------------------------------------------------------===//
   // Debugging
   //===--------------------------------------------------------------------===//

lib/SIL/IR/SILBasicBlock.cpp

@@ -395,6 +395,15 @@ bool SILBasicBlock::isLegalToHoistInto() const {
   return true;
 }
 
+bool SILBasicBlock::hasPhi() const {
+  if (getArguments().size() == 0)
+    return false;
+  // It is sufficient to check whether the first argument is a phi.  A block
+  // can't have both phis and terminator results.
+  auto *argument = getArguments()[0];
+  return argument->isPhiArgument();
+}
+
 const SILDebugScope *SILBasicBlock::getScopeOfFirstNonMetaInstruction() {
   for (auto &Inst : *this)
     if (Inst.isMetaInstruction())