[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, 3 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 302eea4..395d2af 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -570,7 +570,9 @@ LoopUnrollResult llvm::UnrollLoop(Loop *L, UnrollLoopOptions ULO, LoopInfo *LI,
   for (Loop *SubLoop : *L)
     LoopsToSimplify.insert(SubLoop);
 
-  if (Header->getParent()->isDebugInfoForProfiling())
+  // When a FSDiscriminator is enabled, we don't need to add the multiply
+  // factors to the discriminators.
+  if (Header->getParent()->isDebugInfoForProfiling() && !EnableFSDiscriminator)
     for (BasicBlock *BB : L->getBlocks())
       for (Instruction &I : *BB)
         if (!isa<DbgInfoIntrinsic>(&I))