Enhance synchscope representation

  OpenCL 2.0 introduces the notion of memory scopes in atomic operations to
  global and local memory. These scopes restrict how synchronization is
  achieved, which can result in improved performance.

  This change extends existing notion of synchronization scopes in LLVM to
  support arbitrary scopes expressed as target-specific strings, in addition to
  the already defined scopes (single thread, system).

  The LLVM IR and MIR syntax for expressing synchronization scopes has changed
  to use *syncscope("<scope>")*, where <scope> can be "singlethread" (this
  replaces *singlethread* keyword), or a target-specific name. As before, if
  the scope is not specified, it defaults to CrossThread/System scope.

  Implementation details:
    - Mapping from synchronization scope name/string to synchronization scope id
      is stored in LLVM context;
    - CrossThread/System and SingleThread scopes are pre-defined to efficiently
      check for known scopes without comparing strings;
    - Synchronization scope names are stored in SYNC_SCOPE_NAMES_BLOCK in
      the bitcode.

Differential Revision: https://reviews.llvm.org/D21723



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307722 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 18 insertions, 0 deletions

diff --git a/lib/IR/LLVMContext.cpp b/lib/IR/LLVMContext.cpp
index 2e13f362344..1463cdb60fb 100644
--- a/lib/IR/LLVMContext.cpp
+++ b/lib/IR/LLVMContext.cpp
@@ -81,6 +81,16 @@ LLVMContext::LLVMContext() : pImpl(new LLVMContextImpl(*this)) {
   assert(GCTransitionEntry->second == LLVMContext::OB_gc_transition &&
          "gc-transition operand bundle id drifted!");
   (void)GCTransitionEntry;
+
+  SyncScope::ID SingleThreadSSID =
+      pImpl->getOrInsertSyncScopeID("singlethread");
+  assert(SingleThreadSSID == SyncScope::SingleThread &&
+         "singlethread synchronization scope ID drifted!");
+
+  SyncScope::ID SystemSSID =
+      pImpl->getOrInsertSyncScopeID("");
+  assert(SystemSSID == SyncScope::System &&
+         "system synchronization scope ID drifted!");
 }
 
 LLVMContext::~LLVMContext() { delete pImpl; }
@@ -255,6 +265,14 @@ uint32_t LLVMContext::getOperandBundleTagID(StringRef Tag) const {
   return pImpl->getOperandBundleTagID(Tag);
 }
 
+SyncScope::ID LLVMContext::getOrInsertSyncScopeID(StringRef SSN) {
+  return pImpl->getOrInsertSyncScopeID(SSN);
+}
+
+void LLVMContext::getSyncScopeNames(SmallVectorImpl<StringRef> &SSNs) const {
+  pImpl->getSyncScopeNames(SSNs);
+}
+
 void LLVMContext::setGC(const Function &Fn, std::string GCName) {
   auto It = pImpl->GCNames.find(&Fn);