add a debug dump function for ValueLifetimeAnalysis

Author: eeckstein

include/swift/SILOptimizer/Utils/Local.h

@@ -270,6 +270,9 @@ class ValueLifetimeAnalysis {
   /// It is assumed that \p Inst is located after the value's definition.
   bool isWithinLifetime(SILInstruction *Inst);
 
+  /// For debug dumping.
+  void dump() const;
+
 private:
 
   /// The value.

lib/SILOptimizer/Utils/Local.cpp

@@ -1240,6 +1240,18 @@ bool ValueLifetimeAnalysis::isWithinLifetime(SILInstruction *Inst) {
   llvm_unreachable("Expected to find use of value in block!");
 }
 
+void ValueLifetimeAnalysis::dump() const {
+  llvm::errs() << "lifetime of def: " << *DefValue;
+  for (SILInstruction *Use : UserSet) {
+    llvm::errs() << "  use: " << *Use;
+  }
+  llvm::errs() << "  live blocks:";
+  for (SILBasicBlock *BB : LiveBlocks) {
+    llvm::errs() << ' ' << BB->getDebugID();
+  }
+  llvm::errs() << '\n';
+}
+
 //===----------------------------------------------------------------------===//
 //                    Casts Optimization and Simplification
 //===----------------------------------------------------------------------===//