[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

1 files changed, 9 insertions, 2 deletions

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