[llvm] API for encoding/decoding DWARF discriminators.

Summary:
Added a pair of APIs for encoding/decoding the 3 components of a DWARF discriminator described in http://lists.llvm.org/pipermail/llvm-dev/2016-October/106532.html: the base discriminator, the duplication factor (useful in profile-guided optimization) and the copy index (used to identify copies of code in cases like loop unrolling)

The encoding packs 3 unsigned values in 32 bits. This CL addresses 2 issues:
- communicates overflow back to the user
- supports encoding all 3 components together. Current APIs assume a sequencing of events. For example, creating a new discriminator based on an existing one by changing the base discriminator was not supported.

Reviewers: davidxl, danielcdh, wmi, dblaikie

Reviewed By: dblaikie

Subscribers: zzheng, dmgreen, aprantl, JDevlieghere, llvm-commits

Differential Revision: https://reviews.llvm.org/D55681

llvm-svn: 349973

4 files changed, 50 insertions, 12 deletions

diff --git a/llvm/lib/Transforms/Utils/AddDiscriminators.cpp b/llvm/lib/Transforms/Utils/AddDiscriminators.cpp
index e3ef4236222..1e0fd5588ca 100644
--- a/llvm/lib/Transforms/Utils/AddDiscriminators.cpp
+++ b/llvm/lib/Transforms/Utils/AddDiscriminators.cpp
@@ -209,10 +209,18 @@ static bool addDiscriminators(Function &F) {
       // 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];
-      I.setDebugLoc(DIL->setBaseDiscriminator(Discriminator));
-      LLVM_DEBUG(dbgs() << DIL->getFilename() << ":" << DIL->getLine() << ":"
-                        << DIL->getColumn() << ":" << Discriminator << " " << I
-                        << "\n");
+      auto NewDIL = DIL->setBaseDiscriminator(Discriminator);
+      if (!NewDIL) {
+        LLVM_DEBUG(dbgs() << "Could not encode discriminator: "
+                          << DIL->getFilename() << ":" << DIL->getLine() << ":"
+                          << DIL->getColumn() << ":" << Discriminator << " "
+                          << I << "\n");
+      } else {
+        I.setDebugLoc(NewDIL.getValue());
+        LLVM_DEBUG(dbgs() << DIL->getFilename() << ":" << DIL->getLine() << ":"
+                   << DIL->getColumn() << ":" << Discriminator << " " << I
+                   << "\n");
+      }
       Changed = true;
     }
   }
@@ -239,8 +247,17 @@ static bool addDiscriminators(Function &F) {
           std::make_pair(CurrentDIL->getFilename(), CurrentDIL->getLine());
       if (!CallLocations.insert(L).second) {
         unsigned Discriminator = ++LDM[L];
-        Current->setDebugLoc(CurrentDIL->setBaseDiscriminator(Discriminator));
-        Changed = true;
+        auto NewDIL = CurrentDIL->setBaseDiscriminator(Discriminator);
+        if (!NewDIL) {
+          LLVM_DEBUG(dbgs()
+                     << "Could not encode discriminator: "
+                     << CurrentDIL->getFilename() << ":"
+                     << CurrentDIL->getLine() << ":" << CurrentDIL->getColumn()
+                     << ":" << Discriminator << " " << I << "\n");
+        } else {
+          Current->setDebugLoc(NewDIL.getValue());
+          Changed = true;
+        }
       }
     }
   }
diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 0ed4038cc3e..da7ed2bd165 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -598,8 +598,15 @@ LoopUnrollResult llvm::UnrollLoop(
     for (BasicBlock *BB : L->getBlocks())
       for (Instruction &I : *BB)
         if (!isa<DbgInfoIntrinsic>(&I))
-          if (const DILocation *DIL = I.getDebugLoc())
-            I.setDebugLoc(DIL->cloneWithDuplicationFactor(Count));
+          if (const DILocation *DIL = I.getDebugLoc()) {
+            auto NewDIL = DIL->cloneWithDuplicationFactor(Count);
+            if (NewDIL)
+              I.setDebugLoc(NewDIL.getValue());
+            else
+              LLVM_DEBUG(dbgs()
+                         << "Failed to create new discriminator: "
+                         << DIL->getFilename() << " Line: " << DIL->getLine());
+          }
 
   for (unsigned It = 1; It != Count; ++It) {
     std::vector<BasicBlock*> NewBlocks;
diff --git a/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp b/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
index b5d80f669fb..e26762639c1 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
@@ -300,8 +300,15 @@ LoopUnrollResult llvm::UnrollAndJamLoop(
     for (BasicBlock *BB : L->getBlocks())
       for (Instruction &I : *BB)
         if (!isa<DbgInfoIntrinsic>(&I))
-          if (const DILocation *DIL = I.getDebugLoc())
-            I.setDebugLoc(DIL->cloneWithDuplicationFactor(Count));
+          if (const DILocation *DIL = I.getDebugLoc()) {
+            auto NewDIL = DIL->cloneWithDuplicationFactor(Count);
+            if (NewDIL)
+              I.setDebugLoc(NewDIL.getValue());
+            else
+              LLVM_DEBUG(dbgs()
+                         << "Failed to create new discriminator: "
+                         << DIL->getFilename() << " Line: " << DIL->getLine());
+          }
 
   // Copy all blocks
   for (unsigned It = 1; It != Count; ++It) {
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index c74352cf703..c45dee590b8 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -759,8 +759,15 @@ void InnerLoopVectorizer::setDebugLocFromInst(IRBuilder<> &B, const Value *Ptr)
   if (const Instruction *Inst = dyn_cast_or_null<Instruction>(Ptr)) {
     const DILocation *DIL = Inst->getDebugLoc();
     if (DIL && Inst->getFunction()->isDebugInfoForProfiling() &&
-        !isa<DbgInfoIntrinsic>(Inst))
-      B.SetCurrentDebugLocation(DIL->cloneWithDuplicationFactor(UF * VF));
+        !isa<DbgInfoIntrinsic>(Inst)) {
+      auto NewDIL = DIL->cloneWithDuplicationFactor(UF * VF);
+      if (NewDIL)
+        B.SetCurrentDebugLocation(NewDIL.getValue());
+      else
+        LLVM_DEBUG(dbgs()
+                   << "Failed to create new discriminator: "
+                   << DIL->getFilename() << " Line: " << DIL->getLine());
+    }
     else
       B.SetCurrentDebugLocation(DIL);
   } else