[cleanup] Factor out some checks. NFC.

The core logic in main() is actually pretty simple, but there's lots of
stuff that has been added over time which obscures the flow of the code.
In upcoming patches, I'll be pulling more stuff out of the main
codepath.

I'm open to naming suggestions for these helper functions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215751 91177308-0d34-0410-b5e6-96231b3b80d8

tools/driver/driver.cpp

@@ -293,6 +293,23 @@ namespace {
   };
 }
 
+static void HandleDriverEnvVars(Driver &TheDriver) {
+  // Handle CC_PRINT_OPTIONS and CC_PRINT_OPTIONS_FILE.
+  TheDriver.CCPrintOptions = !!::getenv("CC_PRINT_OPTIONS");
+  if (TheDriver.CCPrintOptions)
+    TheDriver.CCPrintOptionsFilename = ::getenv("CC_PRINT_OPTIONS_FILE");
+
+  // Handle CC_PRINT_HEADERS and CC_PRINT_HEADERS_FILE.
+  TheDriver.CCPrintHeaders = !!::getenv("CC_PRINT_HEADERS");
+  if (TheDriver.CCPrintHeaders)
+    TheDriver.CCPrintHeadersFilename = ::getenv("CC_PRINT_HEADERS_FILE");
+
+  // Handle CC_LOG_DIAGNOSTICS and CC_LOG_DIAGNOSTICS_FILE.
+  TheDriver.CCLogDiagnostics = !!::getenv("CC_LOG_DIAGNOSTICS");
+  if (TheDriver.CCLogDiagnostics)
+    TheDriver.CCLogDiagnosticsFilename = ::getenv("CC_LOG_DIAGNOSTICS_FILE");
+}
+
 int main(int argc_, const char **argv_) {
   llvm::sys::PrintStackTraceOnErrorSignal();
   llvm::PrettyStackTraceProgram X(argc_, argv_);
@@ -396,20 +413,7 @@ int main(int argc_, const char **argv_) {
   llvm::InitializeAllTargets();
   ParseProgName(argv, SavedStrings, TheDriver);
 
-  // Handle CC_PRINT_OPTIONS and CC_PRINT_OPTIONS_FILE.
-  TheDriver.CCPrintOptions = !!::getenv("CC_PRINT_OPTIONS");
-  if (TheDriver.CCPrintOptions)
-    TheDriver.CCPrintOptionsFilename = ::getenv("CC_PRINT_OPTIONS_FILE");
-
-  // Handle CC_PRINT_HEADERS and CC_PRINT_HEADERS_FILE.
-  TheDriver.CCPrintHeaders = !!::getenv("CC_PRINT_HEADERS");
-  if (TheDriver.CCPrintHeaders)
-    TheDriver.CCPrintHeadersFilename = ::getenv("CC_PRINT_HEADERS_FILE");
-
-  // Handle CC_LOG_DIAGNOSTICS and CC_LOG_DIAGNOSTICS_FILE.
-  TheDriver.CCLogDiagnostics = !!::getenv("CC_LOG_DIAGNOSTICS");
-  if (TheDriver.CCLogDiagnostics)
-    TheDriver.CCLogDiagnosticsFilename = ::getenv("CC_LOG_DIAGNOSTICS_FILE");
+  HandleDriverEnvVars(TheDriver);
 
   std::unique_ptr<Compilation> C(TheDriver.BuildCompilation(argv));
   int Res = 0;