[PM] Run IndirectCallPromotion only when PGO is enabled

[davide]

Summary

Saves a bit of compile time. In any case, it's unneeded.

[davidxl]

lgtm

lib/Transforms/IPO/PassManagerBuilder.cpp

if (EnablePGOInstrGen) {
     // Add the profile lowering pass.
     InstrProfOptions Options;
     if (!PGOInstrGen.empty())
       Options.InstrProfileOutput = PGOInstrGen;
     MPM.add(createInstrProfilingLegacyPass(Options));
   }
   if (!PGOInstrUse.empty())
     MPM.add(createPGOInstrumentationUseLegacyPass(PGOInstrUse));
+  // Indirect call promotion that promotes intra-module targets only.
+  // For ThinLTO this is done earlier due to interactions with globalopt
+  // for imported functions. We don't run this at -O0.
+  if (OptLevel > 0)
+    MPM.add(
+        createPGOIndirectCallPromotionLegacyPass(false, !PGOSampleUse.empty()));
 }
 void PassManagerBuilder::addFunctionSimplificationPasses(
     legacy::PassManagerBase &MPM) {
   // Start of function pass.
   // Break up aggregate allocas, using SSAUpdater.
   MPM.add(createSROAPass());
   MPM.add(createEarlyCSEPass());              // Catch trivial redundancies
   if (EnableGVNHoist)
if (!DisableUnitAtATime) {
     addInstructionCombiningPass(MPM); // Clean up after IPCP & DAE
     addExtensionsToPM(EP_Peephole, MPM);
     MPM.add(createCFGSimplificationPass()); // Clean up after IPCP & DAE
   }
 
   // For SamplePGO in ThinLTO compile phase, we do not want to do indirect
   // call promotion as it will change the CFG too much to make the 2nd
   // profile annotation in backend more difficult.
-  if (!PerformThinLTO && !PrepareForThinLTOUsingPGOSampleProfile) {
-    /// PGO instrumentation is added during the compile phase for ThinLTO, do
-    /// not run it a second time
+  // PGO instrumentation is added during the compile phase for ThinLTO, do
+  // not run it a second time
+  if (!PerformThinLTO && !PrepareForThinLTOUsingPGOSampleProfile)
     addPGOInstrPasses(MPM);
-    // Indirect call promotion that promotes intra-module targets only.
-    // For ThinLTO this is done earlier due to interactions with globalopt
-    // for imported functions.
-    MPM.add(
-        createPGOIndirectCallPromotionLegacyPass(false, !PGOSampleUse.empty()));
-  }
 
   if (EnableNonLTOGlobalsModRef)
     // We add a module alias analysis pass here. In part due to bugs in the
     // analysis infrastructure this "works" in that the analysis stays alive
     // for the entire SCC pass run below.
     MPM.add(createGlobalsAAWrapperPass());
 
   // Start of CallGraph SCC passes.