Replace push_back(Constructor(foo)) with emplace_back(foo) for non-trivial types

If the type isn't trivially moveable emplace can skip a potentially
expensive move. It also saves a couple of characters.


Call sites were found with the ASTMatcher + some semi-automated cleanup.

memberCallExpr(
    argumentCountIs(1), callee(methodDecl(hasName("push_back"))),
    on(hasType(recordDecl(has(namedDecl(hasName("emplace_back")))))),
    hasArgument(0, bindTemporaryExpr(
                       hasType(recordDecl(hasNonTrivialDestructor())),
                       has(constructExpr()))),
    unless(isInTemplateInstantiation()))

No functional change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238602 91177308-0d34-0410-b5e6-96231b3b80d8

lib/ExecutionEngine/ExecutionEngine.cpp

@@ -438,7 +438,7 @@ int ExecutionEngine::runFunctionAsMain(Function *Fn,
       if (NumArgs > 2) {
         std::vector<std::string> EnvVars;
         for (unsigned i = 0; envp[i]; ++i)
-          EnvVars.push_back(envp[i]);
+          EnvVars.emplace_back(envp[i]);
         // Arg #2 = envp.
         GVArgs.push_back(PTOGV(CEnv.reset(Fn->getContext(), this, EnvVars)));
       }

lib/ExecutionEngine/ExecutionEngineBindings.cpp

@@ -254,11 +254,8 @@ int LLVMRunFunctionAsMain(LLVMExecutionEngineRef EE, LLVMValueRef F,
                           unsigned ArgC, const char * const *ArgV,
                           const char * const *EnvP) {
   unwrap(EE)->finalizeObject();
-  
-  std::vector<std::string> ArgVec;
-  for (unsigned I = 0; I != ArgC; ++I)
-    ArgVec.push_back(ArgV[I]);
-  
+
+  std::vector<std::string> ArgVec(ArgV, ArgV + ArgC);
   return unwrap(EE)->runFunctionAsMain(unwrap<Function>(F), ArgVec, EnvP);
 }
 

lib/ExecutionEngine/Interpreter/Execution.cpp

@@ -2079,7 +2079,7 @@ void Interpreter::callFunction(Function *F,
           ECStack.back().Caller.arg_size() == ArgVals.size()) &&
          "Incorrect number of arguments passed into function call!");
   // Make a new stack frame... and fill it in.
-  ECStack.push_back(ExecutionContext());
+  ECStack.emplace_back();
   ExecutionContext &StackFrame = ECStack.back();
   StackFrame.CurFunction = F;