Move helper for getting a terminating musttail call to BasicBlock

[rnk]

Summary

No functional change. To be used in future commits that need to look
for such instructions.

[rnk]

ping

[rnk]

ping

[• rafael]

lgtm

[rnk]

Closed by commit rL215413 (authored by @rnk).

llvm/trunk/include/llvm/IR/BasicBlock.h

 #include "llvm/ADT/ilist.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/SymbolTableListTraits.h"
 #include "llvm/Support/CBindingWrapping.h"
 #include "llvm/Support/DataTypes.h"
 
 namespace llvm {
 
+class CallInst;
 class LandingPadInst;
 class TerminatorInst;
 class LLVMContext;
 class BlockAddress;
 
 template<> struct ilist_traits<Instruction>
   : public SymbolTableListTraits<Instruction, BasicBlock> {
 
public:
 
   const DataLayout *getDataLayout() const;
 
   /// \brief Returns the terminator instruction if the block is well formed or
   /// null if the block is not well formed.
   TerminatorInst *getTerminator();
   const TerminatorInst *getTerminator() const;
 
+  /// \brief Returns the call instruction marked 'musttail' prior to the
+  /// terminating return instruction of this basic block, if such a call is
+  /// present.  Otherwise, returns null.
+  CallInst *getTerminatingMustTailCall();
+  const CallInst *getTerminatingMustTailCall() const {
+    return const_cast<BasicBlock *>(this)->getTerminatingMustTailCall();
+  }
+
   /// \brief Returns a pointer to the first instruction in this block that is
   /// not a PHINode instruction.
   ///
   /// When adding instructions to the beginning of the basic block, they should
   /// be added before the returned value, not before the first instruction,
   /// which might be PHI. Returns 0 is there's no non-PHI instruction.
   Instruction* getFirstNonPHI();
   const Instruction* getFirstNonPHI() const {

llvm/trunk/lib/IR/BasicBlock.cpp

TerminatorInst *BasicBlock::getTerminator() {
   return dyn_cast<TerminatorInst>(&InstList.back());
 }
 
 const TerminatorInst *BasicBlock::getTerminator() const {
   if (InstList.empty()) return nullptr;
   return dyn_cast<TerminatorInst>(&InstList.back());
 }
 
+CallInst *BasicBlock::getTerminatingMustTailCall() {
+  if (InstList.empty())
+    return nullptr;
+  ReturnInst *RI = dyn_cast<ReturnInst>(&InstList.back());
+  if (!RI || RI == &InstList.front())
+    return nullptr;
+
+  Instruction *Prev = RI->getPrevNode();
+  if (!Prev)
+    return nullptr;
+
+  if (Value *RV = RI->getReturnValue()) {
+    if (RV != Prev)
+      return nullptr;
+
+    // Look through the optional bitcast.
+    if (auto *BI = dyn_cast<BitCastInst>(Prev)) {
+      RV = BI->getOperand(0);
+      Prev = BI->getPrevNode();
+      if (!Prev || RV != Prev)
+        return nullptr;
+    }
+  }
+
+  if (auto *CI = dyn_cast<CallInst>(Prev)) {
+    if (CI->isMustTailCall())
+      return CI;
+  }
+  return nullptr;
+}
+
 Instruction* BasicBlock::getFirstNonPHI() {
   BasicBlock::iterator i = begin();
   // All valid basic blocks should have a terminator,
   // which is not a PHINode. If we have an invalid basic
   // block we'll get an assertion failure when dereferencing
   // a past-the-end iterator.
   while (isa<PHINode>(i)) ++i;
   return &*i;

llvm/trunk/lib/Transforms/Utils/InlineFunction.cpp

for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
           DVI->setOperand(2, createInlinedVariable(DVI->getVariable(), 
                                                    InlinedAt, Ctx));
         }
       }
     }
   }
 }
 
-/// Returns a musttail call instruction if one immediately precedes the given
-/// return instruction with an optional bitcast instruction between them.
-static CallInst *getPrecedingMustTailCall(ReturnInst *RI) {
-  Instruction *Prev = RI->getPrevNode();
-  if (!Prev)
-    return nullptr;
-
-  if (Value *RV = RI->getReturnValue()) {
-    if (RV != Prev)
-      return nullptr;
-
-    // Look through the optional bitcast.
-    if (auto *BI = dyn_cast<BitCastInst>(Prev)) {
-      RV = BI->getOperand(0);
-      Prev = BI->getPrevNode();
-      if (!Prev || RV != Prev)
-        return nullptr;
-    }
-  }
-
-  if (auto *CI = dyn_cast<CallInst>(Prev)) {
-    if (CI->isMustTailCall())
-      return CI;
-  }
-  return nullptr;
-}
-
 /// InlineFunction - This function inlines the called function into the basic
 /// block of the caller.  This returns false if it is not possible to inline
 /// this call.  The program is still in a well defined state if this occurs
 /// though.
 ///
 /// Note that this only does one level of inlining.  For example, if the
 /// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
 /// exists in the instruction stream.  Similarly this will inline a recursive
for (unsigned ai = 0, ae = IFI.StaticAllocas.size(); ai != ae; ++ai) {
           }
         }
       }
 
       builder.CreateLifetimeStart(AI, AllocaSize);
       for (ReturnInst *RI : Returns) {
         // Don't insert llvm.lifetime.end calls between a musttail call and a
         // return.  The return kills all local allocas.
-        if (InlinedMustTailCalls && getPrecedingMustTailCall(RI))
+        if (InlinedMustTailCalls &&
+            RI->getParent()->getTerminatingMustTailCall())
           continue;
         IRBuilder<>(RI).CreateLifetimeEnd(AI, AllocaSize);
       }
     }
   }
 
   // If the inlined code contained dynamic alloca instructions, wrap the inlined
   // code with llvm.stacksave/llvm.stackrestore intrinsics.
   if (InlinedFunctionInfo.ContainsDynamicAllocas) {
     Module *M = Caller->getParent();
     // Get the two intrinsics we care about.
     Function *StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave);
     Function *StackRestore=Intrinsic::getDeclaration(M,Intrinsic::stackrestore);
 
     // Insert the llvm.stacksave.
     CallInst *SavedPtr = IRBuilder<>(FirstNewBlock, FirstNewBlock->begin())
       .CreateCall(StackSave, "savedstack");
 
     // Insert a call to llvm.stackrestore before any return instructions in the
     // inlined function.
     for (ReturnInst *RI : Returns) {
       // Don't insert llvm.stackrestore calls between a musttail call and a
       // return.  The return will restore the stack pointer.
-      if (InlinedMustTailCalls && getPrecedingMustTailCall(RI))
+      if (InlinedMustTailCalls && RI->getParent()->getTerminatingMustTailCall())
         continue;
       IRBuilder<>(RI).CreateCall(StackRestore, SavedPtr);
     }
   }
 
   // If we are inlining for an invoke instruction, we must make sure to rewrite
   // any call instructions into invoke instructions.
   if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
     HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);
 
   // Handle any inlined musttail call sites.  In order for a new call site to be
   // musttail, the source of the clone and the inlined call site must have been
   // musttail.  Therefore it's safe to return without merging control into the
   // phi below.
   if (InlinedMustTailCalls) {
     // Check if we need to bitcast the result of any musttail calls.
     Type *NewRetTy = Caller->getReturnType();
     bool NeedBitCast = !TheCall->use_empty() && TheCall->getType() != NewRetTy;
 
     // Handle the returns preceded by musttail calls separately.
     SmallVector<ReturnInst *, 8> NormalReturns;
     for (ReturnInst *RI : Returns) {
-      CallInst *ReturnedMustTail = getPrecedingMustTailCall(RI);
+      CallInst *ReturnedMustTail =
+          RI->getParent()->getTerminatingMustTailCall();
       if (!ReturnedMustTail) {
         NormalReturns.push_back(RI);
         continue;
       }
       if (!NeedBitCast)
         continue;
 
       // Delete the old return and any preceding bitcast.