Introduce @llvm.experimental.deoptimize

Summary:
This intrinsic, together with deoptimization operand bundles, allow
frontends to express transfer of control and frame-local state from
one (typically more specialized, hence faster) version of a function
into another (typically more generic, hence slower) version.

In languages with a fully integrated managed runtime this intrinsic can
be used to implement "uncommon trap" like functionality.  In unmanaged
languages like C and C++, this intrinsic can be used to represent the
slow paths of specialized functions.

Note: this change does not address how `@llvm.experimental_deoptimize`
is lowered.  That will be done in a later change.

Reviewers: chandlerc, rnk, atrick, reames

Subscribers: llvm-commits, kmod, mjacob, maksfb, mcrosier, JosephTremoulet

Differential Revision: http://reviews.llvm.org/D17732

llvm-svn: 263281

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
index 89a1d74..9f806fa 100644
--- a/llvm/lib/IR/BasicBlock.cpp
+++ b/llvm/lib/IR/BasicBlock.cpp
@@ -162,6 +162,21 @@ CallInst *BasicBlock::getTerminatingMustTailCall() {
   return nullptr;
 }
 
+CallInst *BasicBlock::getTerminatingDeoptimizeCall() {
+  if (InstList.empty())
+    return nullptr;
+  auto *RI = dyn_cast<ReturnInst>(&InstList.back());
+  if (!RI || RI == &InstList.front())
+    return nullptr;
+
+  if (auto *CI = dyn_cast_or_null<CallInst>(RI->getPrevNode()))
+    if (Function *F = CI->getCalledFunction())
+      if (F->getIntrinsicID() == Intrinsic::experimental_deoptimize)
+        return CI;
+
+  return nullptr;
+}
+
 Instruction* BasicBlock::getFirstNonPHI() {
   for (Instruction &I : *this)
     if (!isa<PHINode>(I))