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)));
       }