Introduce deoptimization operand bundles

Summary:
This change introduces the notion of "deoptimization" operand bundles.
LLVM can recognize and optimize these in more precise ways than it can a
generic "unknown" operand bundles.

The current form of this special recognition / optimization is an enum
entry in LLVMContext, a LangRef blurb and a verifier rule.  Over time we
will teach LLVM to do more aggressive optimization around deoptimization
operand bundles, exploiting known facts about kinds of state
deoptimization operand bundles are allowed to track.

Reviewers: reames, majnemer, chandlerc, dexonsmith

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14551

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252806 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/IR/LLVMContext.cpp b/lib/IR/LLVMContext.cpp
index cecc6335ef1..af998c86135 100644
--- a/lib/IR/LLVMContext.cpp
+++ b/lib/IR/LLVMContext.cpp
@@ -127,6 +127,11 @@ LLVMContext::LLVMContext() : pImpl(new LLVMContextImpl(*this)) {
   unsigned AlignID = getMDKindID("align");
   assert(AlignID == MD_align && "align kind id drifted");
   (void)AlignID;
+
+  auto *DeoptEntry = pImpl->getOrInsertBundleTag("deopt");
+  assert(DeoptEntry->second == LLVMContext::OB_deopt &&
+         "deopt operand bundle id drifted!");
+  (void)DeoptEntry;
 }
 LLVMContext::~LLVMContext() { delete pImpl; }