Apply most suggestions of clang-tidy's performance-unnecessary-value-param

Avoids unnecessary copies. All changes audited & pass tests with asan.
No functional change intended.

llvm-svn: 272190
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index d614dfd..b66084b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -178,7 +178,7 @@
   AddStackValue();
 }
 
-void DwarfExpression::AddUnsignedConstant(APInt Value) {
+void DwarfExpression::AddUnsignedConstant(const APInt &Value) {
   unsigned Size = Value.getBitWidth();
   const uint64_t *Data = Value.getRawData();
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 318d8d3..e8a8025 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -100,7 +100,7 @@
   /// Emit an unsigned constant.
   void AddUnsignedConstant(unsigned Value);
   /// Emit an unsigned constant.
-  void AddUnsignedConstant(APInt Value);
+  void AddUnsignedConstant(const APInt &Value);
 
   /// \brief Emit an entire expression on top of a machine register location.
   ///