[PGO] Add ability to mark cold functions as optsize/minsize/optnone (#69030)

The performance of cold functions shouldn't matter too much, so if we
care about binary sizes, add an option to mark cold functions as
optsize/minsize for binary size, or optnone for compile times [1]. Clang
patch will be in a future patch.

This is intended to replace `shouldOptimizeForSize(Function&, ...)`.
We've seen multiple cases where calls to this expensive function, if not
careful, can blow up compile times. I will clean up users of that
function in a followup patch.

Initial version: https://reviews.llvm.org/D149800

[1]
https://discourse.llvm.org/t/rfc-new-feature-proposal-de-optimizing-cold-functions-using-pgo-info/56388

1 files changed, 8 insertions, 4 deletions

diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
index ccc4276..7b3a759 100644
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -243,19 +243,23 @@ static void runNewPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
   if (!Conf.SampleProfile.empty())
     PGOOpt = PGOOptions(Conf.SampleProfile, "", Conf.ProfileRemapping,
                         /*MemoryProfile=*/"", FS, PGOOptions::SampleUse,
-                        PGOOptions::NoCSAction, true);
+                        PGOOptions::NoCSAction,
+                        PGOOptions::ColdFuncOpt::Default, true);
   else if (Conf.RunCSIRInstr) {
     PGOOpt = PGOOptions("", Conf.CSIRProfile, Conf.ProfileRemapping,
                         /*MemoryProfile=*/"", FS, PGOOptions::IRUse,
-                        PGOOptions::CSIRInstr, Conf.AddFSDiscriminator);
+                        PGOOptions::CSIRInstr, PGOOptions::ColdFuncOpt::Default,
+                        Conf.AddFSDiscriminator);
   } else if (!Conf.CSIRProfile.empty()) {
     PGOOpt = PGOOptions(Conf.CSIRProfile, "", Conf.ProfileRemapping,
                         /*MemoryProfile=*/"", FS, PGOOptions::IRUse,
-                        PGOOptions::CSIRUse, Conf.AddFSDiscriminator);
+                        PGOOptions::CSIRUse, PGOOptions::ColdFuncOpt::Default,
+                        Conf.AddFSDiscriminator);
     NoPGOWarnMismatch = !Conf.PGOWarnMismatch;
   } else if (Conf.AddFSDiscriminator) {
     PGOOpt = PGOOptions("", "", "", /*MemoryProfile=*/"", nullptr,
-                        PGOOptions::NoAction, PGOOptions::NoCSAction, true);
+                        PGOOptions::NoAction, PGOOptions::NoCSAction,
+                        PGOOptions::ColdFuncOpt::Default, true);
   }
   TM->setPGOOption(PGOOpt);