Add a -time-compilations=<N> option to llc.

This causes llc to repeat the module compilation N times, making it
possible to get more accurate information from -time-passes when
compiling small modules.

llvm-svn: 169040

llvm/tools/llc/llc.cpp

@@ -51,6 +51,11 @@ InputFilename(cl::Positional, cl::desc("<input bitcode>"), cl::init("-"));
 static cl::opt<std::string>
 OutputFilename("o", cl::desc("Output filename"), cl::value_desc("filename"));
 
+static cl::opt<unsigned>
+TimeCompilations("time-compilations", cl::Hidden, cl::init(1u),
+                 cl::value_desc("N"),
+                 cl::desc("Repeat compilation N times for timing"));
+
 // Determine optimization level.
 static cl::opt<char>
 OptLevel("O",
@@ -71,6 +76,8 @@ DisableSimplifyLibCalls("disable-simplify-libcalls",
                         cl::desc("Disable simplify-libcalls"),
                         cl::init(false));
 
+static int compileModule(char**, LLVMContext&);
+
 // GetFileNameRoot - Helper function to get the basename of a filename.
 static inline std::string
 GetFileNameRoot(const std::string &InputFilename) {
@@ -181,6 +188,15 @@ int main(int argc, char **argv) {
 
   cl::ParseCommandLineOptions(argc, argv, "llvm system compiler\n");
 
+  // Compile the module TimeCompilations times to give better compile time
+  // metrics.
+  for (unsigned I = TimeCompilations; I; --I)
+    if (int RetVal = compileModule(argv, Context))
+      return RetVal;
+  return 0;
+}
+
+static int compileModule(char **argv, LLVMContext &Context) {
   // Load the module to be compiled...
   SMDiagnostic Err;
   std::auto_ptr<Module> M;