Change LTO to run the global opt pass twice.

- This matches llvm-ld.

It took a bit of archeology to figure out what the right thing to do was
(whether this was intentionally added or intentionally removed). My final
conclusion is that Chris added this intentionally here:
  http://llvm.org/viewvc/llvm-project?view=rev&revision=16913
but the changes weren't propogated to llvm-ld until here:
  http://llvm.org/viewvc/llvm-project?view=rev&revision=34058
which was after lto.cpp had been cloned off (of llvm-ld), here:
  http://llvm.org/viewvc/llvm-project?view=rev&revision=29494

From the commit message, it looks like the motivation for running global opt
again is because we ran it prior to inlining. Based on that I updated the
comment and also only run the pass if we actually ran the inliner.

Chris, please review.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72811 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/StandardPasses.h

@@ -60,15 +60,10 @@ namespace llvm {
   ///
   /// Internalize - Run the internalize pass.
   /// RunInliner - Use a function inlining pass.
-  /// RunSecondGlobalOpt - Run the global optimizer pass twice.
   /// VerifyEach - Run the verifier after each pass.
-  //
-  // FIXME: RunSecondGlobalOpt should go away once we resolve which of LTO or
-  // llvm-ld is better.
   static inline void createStandardLTOPasses(PassManager *PM,
                                              bool Internalize,
                                              bool RunInliner,
-                                             bool RunSecondGlobalOpt,
                                              bool VerifyEach);
 
   // Implementations
@@ -173,7 +168,6 @@ namespace llvm {
   static inline void createStandardLTOPasses(PassManager *PM,
                                              bool Internalize,
                                              bool RunInliner,
-                                             bool RunSecondGlobalOpt,
                                              bool VerifyEach) {
     // Now that composite has been compiled, scan through the module, looking
     // for a main function.  If main is defined, mark all other functions
@@ -207,8 +201,8 @@ namespace llvm {
       addOnePass(PM, createFunctionInliningPass(), VerifyEach);
 
     addOnePass(PM, createPruneEHPass(), VerifyEach);   // Remove dead EH info.
-    // Optimize globals again.
-    if (RunSecondGlobalOpt)
+    // Optimize globals again if we ran the inliner.
+    if (RunInliner)
       addOnePass(PM, createGlobalOptimizerPass(), VerifyEach);
     addOnePass(PM, createGlobalDCEPass(), VerifyEach); // Remove dead functions.
 

tools/llvm-ld/Optimize.cpp

@@ -94,7 +94,7 @@ void Optimize(Module* M) {
 
   if (!DisableOptimizations)
     createStandardLTOPasses(&Passes, !DisableInternalize, !DisableInline,
-                            /*RunSecondGlobalOpt=*/true, VerifyEach);
+                            VerifyEach);
 
   // If the -s or -S command line options were specified, strip the symbols out
   // of the resulting program to make it smaller.  -s and -S are GNU ld options

tools/lto/LTOCodeGenerator.cpp

@@ -391,7 +391,6 @@ bool LTOCodeGenerator::generateAssemblyCode(raw_ostream& out,
     passes.add(new TargetData(*_target->getTargetData()));
     
     createStandardLTOPasses(&passes, /*Internalize=*/ false, !DisableInline,
-                            /*RunSecondGlobalOpt=*/ false, 
                             /*VerifyEach=*/ false);
 
     // Make sure everything is still good.