[SampleFDO] New hierarchical discriminator for Flow Sensitive SampleFDO

This patch implements first part of Flow Sensitive SampleFDO (FSAFDO).
It has the following changes:
(1) disable current discriminator encoding scheme,
(2) new hierarchical discriminator for FSAFDO.

For this patch, option "-enable-fs-discriminator=true" turns on the new
functionality. Option "-enable-fs-discriminator=false" (the default)
keeps the current SampleFDO behavior. When the fs-discriminator is
enabled, we insert a flag variable, namely, llvm_fs_discriminator, to
the object. This symbol will checked by create_llvm_prof tool, and used
to generate a profile with FS-AFDO discriminators enabled. If this
happens, for an extbinary format profile, create_llvm_prof tool
will add a flag to profile summary section.

Differential Revision: https://reviews.llvm.org/D102246

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
index 35fa9bd..4e4ba4f 100644
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -215,10 +215,15 @@ static void runNewPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
                         PGOOptions::SampleUse, PGOOptions::NoCSAction, true);
   else if (Conf.RunCSIRInstr) {
     PGOOpt = PGOOptions("", Conf.CSIRProfile, Conf.ProfileRemapping,
-                        PGOOptions::IRUse, PGOOptions::CSIRInstr);
+                        PGOOptions::IRUse, PGOOptions::CSIRInstr,
+                        Conf.AddFSDiscriminator);
   } else if (!Conf.CSIRProfile.empty()) {
     PGOOpt = PGOOptions(Conf.CSIRProfile, "", Conf.ProfileRemapping,
-                        PGOOptions::IRUse, PGOOptions::CSIRUse);
+                        PGOOptions::IRUse, PGOOptions::CSIRUse,
+                        Conf.AddFSDiscriminator);
+  } else if (Conf.AddFSDiscriminator) {
+    PGOOpt = PGOOptions("", "", "", PGOOptions::NoAction,
+                        PGOOptions::NoCSAction, true);
   }
 
   LoopAnalysisManager LAM;