From 2d16145acfb67c7498cf43a7a3fd04b543a2a767 Mon Sep 17 00:00:00 2001
From: Sanjoy Das <sanjoy@playingwithpointers.com>
Date: Wed, 18 Nov 2015 06:23:38 +0000
Subject: Teach the inliner to track deoptimization state

Summary:
This change teaches LLVM's inliner to track and suitably adjust
deoptimization state (tracked via deoptimization operand bundles) as it
inlines through call sites.  The operation is described in more detail
in the LangRef changes.

Reviewers: reames, majnemer, chandlerc, dexonsmith

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14552

llvm-svn: 253438
---
 llvm/lib/Transforms/Utils/InlineFunction.cpp | 85 ++++++++++++++++++++++++++--
 1 file changed, 80 insertions(+), 5 deletions(-)

(limited to 'llvm/lib/Transforms/Utils/InlineFunction.cpp')

diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index 1507d313aa0..dfb028111e9 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -208,8 +208,21 @@ HandleCallsInBlockInlinedThroughInvoke(BasicBlock *BB, BasicBlock *UnwindEdge) {
     // Create the new invoke instruction.
     ImmutableCallSite CS(CI);
     SmallVector<Value*, 8> InvokeArgs(CS.arg_begin(), CS.arg_end());
-    InvokeInst *II = InvokeInst::Create(CI->getCalledValue(), Split, UnwindEdge,
-                                        InvokeArgs, CI->getName(), BB);
+    SmallVector<OperandBundleDef, 1> OpBundles;
+
+    // Copy the OperandBundeUse instances to OperandBundleDefs.  These two are
+    // *different* representations of operand bundles: see the documentation in
+    // InstrTypes.h for more details.
+    for (unsigned i = 0, e = CS.getNumOperandBundles(); i != e; ++i)
+      OpBundles.emplace_back(CS.getOperandBundleAt(i));
+
+    // Note: we're round tripping operand bundles through memory here, and that
+    // can potentially be avoided with a cleverer API design that we do not have
+    // as of this time.
+
+    InvokeInst *II =
+        InvokeInst::Create(CI->getCalledValue(), Split, UnwindEdge, InvokeArgs,
+                           OpBundles, CI->getName(), BB);
     II->setDebugLoc(CI->getDebugLoc());
     II->setCallingConv(CI->getCallingConv());
     II->setAttributes(CI->getAttributes());
@@ -1029,9 +1042,16 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
       CalledFunc->isDeclaration() || // call, or call to a vararg function!
       CalledFunc->getFunctionType()->isVarArg()) return false;
 
-  // The inliner does not know how to inline through calls with operand bundles.
-  if (CS.hasOperandBundles())
-    return false;
+  // The inliner does not know how to inline through calls with operand bundles
+  // in general ...
+  if (CS.hasOperandBundles()) {
+    // ... but it knows how to inline through "deopt" operand bundles.
+    bool CanInline =
+        CS.getNumOperandBundles() == 1 &&
+        CS.getOperandBundleAt(0).getTagID() == LLVMContext::OB_deopt;
+    if (!CanInline)
+      return false;
+  }
 
   // If the call to the callee cannot throw, set the 'nounwind' flag on any
   // calls that we inline.
@@ -1138,6 +1158,61 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
       HandleByValArgumentInit(Init.first, Init.second, Caller->getParent(),
                               &*FirstNewBlock, IFI);
 
+    if (CS.hasOperandBundles()) {
+      auto ParentDeopt = CS.getOperandBundleAt(0);
+      assert(ParentDeopt.getTagID() == LLVMContext::OB_deopt &&
+             "Checked on entry!");
+
+      SmallVector<OperandBundleDef, 2> OpDefs;
+
+      for (auto &VH : InlinedFunctionInfo.OperandBundleCallSites) {
+        Instruction *I = VH;
+
+        OpDefs.clear();
+
+        CallSite ICS(I);
+        OpDefs.reserve(ICS.getNumOperandBundles());
+
+        for (unsigned i = 0, e = ICS.getNumOperandBundles(); i < e; ++i) {
+          auto ChildOB = ICS.getOperandBundleAt(i);
+          if (ChildOB.getTagID() != LLVMContext::OB_deopt) {
+            // If the inlined call has other operand bundles, let them be
+            OpDefs.emplace_back(ChildOB);
+            continue;
+          }
+
+          // It may be useful to separate this logic (of handling operand
+          // bundles) out to a separate "policy" component if this gets crowded.
+          // Prepend the parent's deoptimization continuation to the newly
+          // inlined call's deoptimization continuation.
+          std::vector<Value *> MergedDeoptArgs;
+          MergedDeoptArgs.reserve(ParentDeopt.Inputs.size() +
+                                  ChildOB.Inputs.size());
+
+          MergedDeoptArgs.insert(MergedDeoptArgs.end(),
+                                 ParentDeopt.Inputs.begin(),
+                                 ParentDeopt.Inputs.end());
+          MergedDeoptArgs.insert(MergedDeoptArgs.end(), ChildOB.Inputs.begin(),
+                                 ChildOB.Inputs.end());
+
+          OpDefs.emplace_back("deopt", std::move(MergedDeoptArgs));
+        }
+
+        Instruction *NewI = nullptr;
+        if (isa<CallInst>(I))
+          NewI = CallInst::Create(cast<CallInst>(I), OpDefs, I);
+        else
+          NewI = InvokeInst::Create(cast<InvokeInst>(I), OpDefs, I);
+
+        // Note: the RAUW does the appropriate fixup in VMap, so we need to do
+        // this even if the call returns void.
+        I->replaceAllUsesWith(NewI);
+
+        VH = nullptr;
+        I->eraseFromParent();
+      }
+    }
+
     // Update the callgraph if requested.
     if (IFI.CG)
       UpdateCallGraphAfterInlining(CS, FirstNewBlock, VMap, IFI);
-- 
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