Encode duplication factor from loop vectorization and loop unrolling to discriminator.

Summary:
This patch starts the implementation as discuss in the following RFC: http://lists.llvm.org/pipermail/llvm-dev/2016-October/106532.html

When optimization duplicates code that will scale down the execution count of a basic block, we will record the duplication factor as part of discriminator so that the offline process tool can find the duplication factor and collect the accurate execution frequency of the corresponding source code. Two important optimization that fall into this category is loop vectorization and loop unroll. This patch records the duplication factor for these 2 optimizations.

The recording will be guarded by a flag encode-duplication-in-discriminators, which is off by default.

Reviewers: probinson, aprantl, davidxl, hfinkel, echristo

Reviewed By: hfinkel

Subscribers: mehdi_amini, anemet, mzolotukhin, llvm-commits

Differential Revision: https://reviews.llvm.org/D26420

llvm-svn: 294782

1 files changed, 4 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Utils/AddDiscriminators.cpp b/llvm/lib/Transforms/Utils/AddDiscriminators.cpp
index 2e95926c0b3..0d8ee844d3f 100644
--- a/llvm/lib/Transforms/Utils/AddDiscriminators.cpp
+++ b/llvm/lib/Transforms/Utils/AddDiscriminators.cpp
@@ -190,8 +190,8 @@ static bool addDiscriminators(Function &F) {
       // discriminator is needed to distinguish both instructions.
       // Only the lowest 7 bits are used to represent a discriminator to fit
       // it in 1 byte ULEB128 representation.
-      unsigned Discriminator = (R.second ? ++LDM[L] : LDM[L]) & 0x7f;
-      I.setDebugLoc(DIL->cloneWithDiscriminator(Discriminator));
+      unsigned Discriminator = R.second ? ++LDM[L] : LDM[L];
+      I.setDebugLoc(DIL->setBaseDiscriminator(Discriminator));
       DEBUG(dbgs() << DIL->getFilename() << ":" << DIL->getLine() << ":"
                    << DIL->getColumn() << ":" << Discriminator << " " << I
                    << "\n");
@@ -216,8 +216,8 @@ static bool addDiscriminators(Function &F) {
       Location L =
           std::make_pair(CurrentDIL->getFilename(), CurrentDIL->getLine());
       if (!CallLocations.insert(L).second) {
-        Current->setDebugLoc(
-            CurrentDIL->cloneWithDiscriminator((++LDM[L]) & 0x7f));
+        unsigned Discriminator = ++LDM[L];
+        Current->setDebugLoc(CurrentDIL->setBaseDiscriminator(Discriminator));
         Changed = true;
       }
     }