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

2 files changed, 38 insertions, 0 deletions

diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
index 89a1d744441..9f806fad680 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))
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 48792fbfc42..9d9fe7d376d 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -4082,6 +4082,29 @@ void Verifier::visitIntrinsicCallSite(Intrinsic::ID ID, CallSite CS) {
            "masked_store: vector mask must be same length as data", CS);
     break;
   }
+
+  case Intrinsic::experimental_deoptimize: {
+    Assert(CS.isCall(), "experimental_deoptimize cannot be invoked", CS);
+    Assert(CS.countOperandBundlesOfType(LLVMContext::OB_deopt) == 1,
+           "experimental_deoptimize must have exactly one "
+           "\"deopt\" operand bundle");
+    Assert(CS.getType() == CS.getInstruction()->getFunction()->getReturnType(),
+           "experimental_deoptimize return type must match caller return type");
+
+    if (CS.isCall()) {
+      auto *DeoptCI = CS.getInstruction();
+      auto *RI = dyn_cast<ReturnInst>(DeoptCI->getNextNode());
+      Assert(RI,
+             "calls to experimental_deoptimize must be followed by a return");
+
+      if (!CS.getType()->isVoidTy() && RI)
+        Assert(RI->getReturnValue() == DeoptCI,
+               "calls to experimental_deoptimize must be followed by a return "
+               "of the value computed by experimental_deoptimize");
+    }
+
+    break;
+  }
   };
 }