[clang][Tooling] Optimize addTargetAndMode in case of invalid modes

[kadircet]

Summary

This skips searching for target related flags in the existing args if
we don't have a valid target to insert.

Depends on D85076

[hokein]

clang/lib/Tooling/Tooling.cpp

263

While this is an optimization, I find the code is a bit harder to follow, with this patch AlreadyHasTarget has two semantic meanings: 1) for has target and 2) for target mode is valid.

I guess we could do it like

if (TargetMode.TargetIsValid) {
  // set the TargetOPT, TargetOPTLegacy variables
  // search the command line of the target opt.
  // insert to CommandLine.
}

maybe we could do the same thing for the DriverMode

if (TargetMode.DriverMode) {
  ...
}

[kadircet]

clang/lib/Tooling/Tooling.cpp

263

i would rather not duplicate the loop, what about renaming AlreadyHastTarget to ShouldAddTarget (likewise for AlyreadyHasMode) ?

[hokein]

clang/lib/Tooling/Tooling.cpp

263

I'd not worry too much about the loop, but rename also seems ok to me.

[kadircet]

• Rename AlreadyHas to ShouldAdd (and revert the logic)

[kadircet]

• Change bitwise assignment to logical operators, as bitwise operators do not have short-circuting.

clang/lib/Tooling/Tooling.cpp

const std::string TargetOPT =
       Table.getOption(driver::options::OPT_target).getPrefixedName();
   // -target X
   const std::string TargetOPTLegacy =
       Table.getOption(driver::options::OPT_target_legacy_spelling)
           .getPrefixedName();
   // --driver-mode=X
   const std::string DriverModeOPT =
       Table.getOption(driver::options::OPT_driver_mode).getPrefixedName();
-  bool AlreadyHasTarget = false;
-  bool AlreadyHasMode = false;
+  auto TargetMode =
+      driver::ToolChain::getTargetAndModeFromProgramName(InvokedAs);
+  // No need to search for target args if we don't have a target/mode to insert.
+  bool ShouldAddTarget = TargetMode.TargetIsValid;
+  bool ShouldAddMode = TargetMode.DriverMode != nullptr;
   // Skip CommandLine[0].
   for (auto Token = ++CommandLine.begin(); Token != CommandLine.end();
        ++Token) {
     StringRef TokenRef(*Token);
-    AlreadyHasTarget |=
-        TokenRef.startswith(TargetOPT) || TokenRef.equals(TargetOPTLegacy);
-    AlreadyHasMode |= TokenRef.startswith(DriverModeOPT);
+    ShouldAddTarget = ShouldAddTarget && !TokenRef.startswith(TargetOPT) &&
+                      !TokenRef.equals(TargetOPTLegacy);
+    ShouldAddMode = ShouldAddMode && !TokenRef.startswith(DriverModeOPT);
   }
-  auto TargetMode =
-      driver::ToolChain::getTargetAndModeFromProgramName(InvokedAs);
-  if (!AlreadyHasMode && TargetMode.DriverMode) {
+  if (ShouldAddMode) {
     CommandLine.insert(++CommandLine.begin(), TargetMode.DriverMode);
   }
-  if (!AlreadyHasTarget && TargetMode.TargetIsValid) {
+  if (ShouldAddTarget) {
     CommandLine.insert(++CommandLine.begin(),
                        TargetOPT + TargetMode.TargetPrefix);
   }
 }
 
 } // namespace tooling
 } // namespace clang