/// Fix-up phi nodes in an invoke instruction's normal destination.
///
/// After versioning an invoke instruction, values coming from the original
-/// block will now either be coming from the original block or the "else" block.
+/// block will now be coming from the "merge" block. For example, in the code
+/// below:
+///
+/// then_bb:
+/// %t0 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
+///
+/// else_bb:
+/// %t1 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
+///
+/// merge_bb:
+/// %t2 = phi i32 [ %t0, %then_bb ], [ %t1, %else_bb ]
+/// br %normal_dst
+///
+/// normal_dst:
+/// %t3 = phi i32 [ %x, %orig_bb ], ...
+///
+/// "orig_bb" is no longer a predecessor of "normal_dst", so the phi nodes in
+/// "normal_dst" must be fixed to refer to "merge_bb":
+///
+/// normal_dst:
+/// %t3 = phi i32 [ %x, %merge_bb ], ...
+///
static void fixupPHINodeForNormalDest(InvokeInst *Invoke, BasicBlock *OrigBlock,
- BasicBlock *ElseBlock,
- Instruction *NewInst) {
+ BasicBlock *MergeBlock) {
for (auto &I : *Invoke->getNormalDest()) {
auto *Phi = dyn_cast<PHINode>(&I);
if (!Phi)
int Idx = Phi->getBasicBlockIndex(OrigBlock);
if (Idx == -1)
continue;
- Value *V = Phi->getIncomingValue(Idx);
- if (dyn_cast<Instruction>(V) == Invoke) {
- Phi->setIncomingBlock(Idx, ElseBlock);
- Phi->addIncoming(NewInst, OrigBlock);
- continue;
- }
- Phi->addIncoming(V, ElseBlock);
+ Phi->setIncomingBlock(Idx, MergeBlock);
}
}
///
/// After versioning an invoke instruction, values coming from the original
/// block will now be coming from either the "then" block or the "else" block.
+/// For example, in the code below:
+///
+/// then_bb:
+/// %t0 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
+///
+/// else_bb:
+/// %t1 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
+///
+/// unwind_dst:
+/// %t3 = phi i32 [ %x, %orig_bb ], ...
+///
+/// "orig_bb" is no longer a predecessor of "unwind_dst", so the phi nodes in
+/// "unwind_dst" must be fixed to refer to "then_bb" and "else_bb":
+///
+/// unwind_dst:
+/// %t3 = phi i32 [ %x, %then_bb ], [ %x, %else_bb ], ...
+///
static void fixupPHINodeForUnwindDest(InvokeInst *Invoke, BasicBlock *OrigBlock,
BasicBlock *ThenBlock,
BasicBlock *ElseBlock) {
}
}
-/// Get the phi node having the returned value of a call or invoke instruction
-/// as it's operand.
-static bool getRetPhiNode(Instruction *Inst, BasicBlock *Block) {
- BasicBlock *FromBlock = Inst->getParent();
- for (auto &I : *Block) {
- PHINode *PHI = dyn_cast<PHINode>(&I);
- if (!PHI)
- break;
- int Idx = PHI->getBasicBlockIndex(FromBlock);
- if (Idx == -1)
- continue;
- auto *V = PHI->getIncomingValue(Idx);
- if (V == Inst)
- return true;
- }
- return false;
-}
-
/// Create a phi node for the returned value of a call or invoke instruction.
///
/// After versioning a call or invoke instruction that returns a value, we have
/// to merge the value of the original and new instructions. We do this by
/// creating a phi node and replacing uses of the original instruction with this
/// phi node.
-static void createRetPHINode(Instruction *OrigInst, Instruction *NewInst) {
+///
+/// For example, if \p OrigInst is defined in "else_bb" and \p NewInst is
+/// defined in "then_bb", we create the following phi node:
+///
+/// ; Uses of the original instruction are replaced by uses of the phi node.
+/// %t0 = phi i32 [ %orig_inst, %else_bb ], [ %new_inst, %then_bb ],
+///
+static void createRetPHINode(Instruction *OrigInst, Instruction *NewInst,
+ BasicBlock *MergeBlock, IRBuilder<> &Builder) {
if (OrigInst->getType()->isVoidTy() || OrigInst->use_empty())
return;
- BasicBlock *RetValBB = NewInst->getParent();
- if (auto *Invoke = dyn_cast<InvokeInst>(NewInst))
- RetValBB = Invoke->getNormalDest();
- BasicBlock *PhiBB = RetValBB->getSingleSuccessor();
-
- if (getRetPhiNode(OrigInst, PhiBB))
- return;
-
- IRBuilder<> Builder(&PhiBB->front());
+ Builder.SetInsertPoint(&MergeBlock->front());
PHINode *Phi = Builder.CreatePHI(OrigInst->getType(), 0);
SmallVector<User *, 16> UsersToUpdate;
for (User *U : OrigInst->users())
for (User *U : UsersToUpdate)
U->replaceUsesOfWith(OrigInst, Phi);
Phi->addIncoming(OrigInst, OrigInst->getParent());
- Phi->addIncoming(NewInst, RetValBB);
+ Phi->addIncoming(NewInst, NewInst->getParent());
}
/// Cast a call or invoke instruction to the given type.
/// that of the callee. If this is the case, we have to cast the returned value
/// to the correct type. The location of the cast depends on if we have a call
/// or invoke instruction.
-Instruction *createRetBitCast(CallSite CS, Type *RetTy) {
+///
+/// For example, if the call instruction below requires a bitcast after
+/// promotion:
+///
+/// orig_bb:
+/// %t0 = call i32 @func()
+/// ...
+///
+/// The bitcast is placed after the call instruction:
+///
+/// orig_bb:
+/// ; Uses of the original return value are replaced by uses of the bitcast.
+/// %t0 = call i32 @func()
+/// %t1 = bitcast i32 %t0 to ...
+/// ...
+///
+/// A similar transformation is performed for invoke instructions. However,
+/// since invokes are terminating, a new block is created for the bitcast. For
+/// example, if the invoke instruction below requires a bitcast after promotion:
+///
+/// orig_bb:
+/// %t0 = invoke i32 @func() to label %normal_dst unwind label %unwind_dst
+///
+/// The edge between the original block and the invoke's normal destination is
+/// split, and the bitcast is placed there:
+///
+/// orig_bb:
+/// %t0 = invoke i32 @func() to label %split_bb unwind label %unwind_dst
+///
+/// split_bb:
+/// ; Uses of the original return value are replaced by uses of the bitcast.
+/// %t1 = bitcast i32 %t0 to ...
+/// br label %normal_dst
+///
+static void createRetBitCast(CallSite CS, Type *RetTy, CastInst **RetBitCast) {
// Save the users of the calling instruction. These uses will be changed to
// use the bitcast after we create it.
// value. The location depends on if we have a call or invoke instruction.
Instruction *InsertBefore = nullptr;
if (auto *Invoke = dyn_cast<InvokeInst>(CS.getInstruction()))
- InsertBefore = &*Invoke->getNormalDest()->getFirstInsertionPt();
+ InsertBefore =
+ &SplitEdge(Invoke->getParent(), Invoke->getNormalDest())->front();
else
InsertBefore = &*std::next(CS.getInstruction()->getIterator());
// Bitcast the return value to the correct type.
auto *Cast = CastInst::Create(Instruction::BitCast, CS.getInstruction(),
RetTy, "", InsertBefore);
+ if (RetBitCast)
+ *RetBitCast = Cast;
// Replace all the original uses of the calling instruction with the bitcast.
for (User *U : UsersToUpdate)
U->replaceUsesOfWith(CS.getInstruction(), Cast);
-
- return Cast;
}
/// Predicate and clone the given call site.
/// callee. The original call site is moved into the "else" block, and a clone
/// of the call site is placed in the "then" block. The cloned instruction is
/// returned.
+///
+/// For example, the call instruction below:
+///
+/// orig_bb:
+/// %t0 = call i32 %ptr()
+/// ...
+///
+/// Is replace by the following:
+///
+/// orig_bb:
+/// %cond = icmp eq i32 ()* %ptr, @func
+/// br i1 %cond, %then_bb, %else_bb
+///
+/// then_bb:
+/// ; The clone of the original call instruction is placed in the "then"
+/// ; block. It is not yet promoted.
+/// %t1 = call i32 %ptr()
+/// br merge_bb
+///
+/// else_bb:
+/// ; The original call instruction is moved to the "else" block.
+/// %t0 = call i32 %ptr()
+/// br merge_bb
+///
+/// merge_bb:
+/// ; Uses of the original call instruction are replaced by uses of the phi
+/// ; node.
+/// %t2 = phi i32 [ %t0, %else_bb ], [ %t1, %then_bb ]
+/// ...
+///
+/// A similar transformation is performed for invoke instructions. However,
+/// since invokes are terminating, more work is required. For example, the
+/// invoke instruction below:
+///
+/// orig_bb:
+/// %t0 = invoke %ptr() to label %normal_dst unwind label %unwind_dst
+///
+/// Is replace by the following:
+///
+/// orig_bb:
+/// %cond = icmp eq i32 ()* %ptr, @func
+/// br i1 %cond, %then_bb, %else_bb
+///
+/// then_bb:
+/// ; The clone of the original invoke instruction is placed in the "then"
+/// ; block, and its normal destination is set to the "merge" block. It is
+/// ; not yet promoted.
+/// %t1 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
+///
+/// else_bb:
+/// ; The original invoke instruction is moved into the "else" block, and
+/// ; its normal destination is set to the "merge" block.
+/// %t0 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
+///
+/// merge_bb:
+/// ; Uses of the original invoke instruction are replaced by uses of the
+/// ; phi node, and the merge block branches to the normal destination.
+/// %t2 = phi i32 [ %t0, %else_bb ], [ %t1, %then_bb ]
+/// br %normal_dst
+///
static Instruction *versionCallSite(CallSite CS, Value *Callee,
- MDNode *BranchWeights,
- BasicBlock *&ThenBlock,
- BasicBlock *&ElseBlock,
- BasicBlock *&MergeBlock) {
+ MDNode *BranchWeights) {
IRBuilder<> Builder(CS.getInstruction());
Instruction *OrigInst = CS.getInstruction();
+ BasicBlock *OrigBlock = OrigInst->getParent();
// Create the compare. The called value and callee must have the same type to
// be compared.
- auto *LHS =
- Builder.CreateBitCast(CS.getCalledValue(), Builder.getInt8PtrTy());
- auto *RHS = Builder.CreateBitCast(Callee, Builder.getInt8PtrTy());
- auto *Cond = Builder.CreateICmpEQ(LHS, RHS);
+ if (CS.getCalledValue()->getType() != Callee->getType())
+ Callee = Builder.CreateBitCast(Callee, CS.getCalledValue()->getType());
+ auto *Cond = Builder.CreateICmpEQ(CS.getCalledValue(), Callee);
// Create an if-then-else structure. The original instruction is moved into
// the "else" block, and a clone of the original instruction is placed in the
TerminatorInst *ElseTerm = nullptr;
SplitBlockAndInsertIfThenElse(Cond, CS.getInstruction(), &ThenTerm, &ElseTerm,
BranchWeights);
- ThenBlock = ThenTerm->getParent();
- ElseBlock = ElseTerm->getParent();
- MergeBlock = OrigInst->getParent();
+ BasicBlock *ThenBlock = ThenTerm->getParent();
+ BasicBlock *ElseBlock = ElseTerm->getParent();
+ BasicBlock *MergeBlock = OrigInst->getParent();
ThenBlock->setName("if.true.direct_targ");
ElseBlock->setName("if.false.orig_indirect");
NewInst->insertBefore(ThenTerm);
// If the original call site is an invoke instruction, we have extra work to
- // do since invoke instructions are terminating.
+ // do since invoke instructions are terminating. We have to fix-up phi nodes
+ // in the invoke's normal and unwind destinations.
if (auto *OrigInvoke = dyn_cast<InvokeInst>(OrigInst)) {
auto *NewInvoke = cast<InvokeInst>(NewInst);
Builder.SetInsertPoint(MergeBlock);
Builder.CreateBr(OrigInvoke->getNormalDest());
- // Now set the normal destination of new the invoke instruction to be the
+ // Fix-up phi nodes in the original invoke's normal and unwind destinations.
+ fixupPHINodeForNormalDest(OrigInvoke, OrigBlock, MergeBlock);
+ fixupPHINodeForUnwindDest(OrigInvoke, MergeBlock, ThenBlock, ElseBlock);
+
+ // Now set the normal destinations of the invoke instructions to be the
// "merge" block.
+ OrigInvoke->setNormalDest(MergeBlock);
NewInvoke->setNormalDest(MergeBlock);
}
+ // Create a phi node for the returned value of the call site.
+ createRetPHINode(OrigInst, NewInst, MergeBlock, Builder);
+
return NewInst;
}
return true;
}
-static void promoteCall(CallSite CS, Function *Callee, Instruction *&Cast) {
+Instruction *llvm::promoteCall(CallSite CS, Function *Callee,
+ CastInst **RetBitCast) {
assert(!CS.getCalledFunction() && "Only indirect call sites can be promoted");
// Set the called function of the call site to be the given callee.
// If the function type of the call site matches that of the callee, no
// additional work is required.
if (CS.getFunctionType() == Callee->getFunctionType())
- return;
+ return CS.getInstruction();
// Save the return types of the call site and callee.
Type *CallSiteRetTy = CS.getInstruction()->getType();
// If the return type of the call site doesn't match that of the callee, cast
// the returned value to the appropriate type.
if (!CallSiteRetTy->isVoidTy() && CallSiteRetTy != CalleeRetTy)
- Cast = createRetBitCast(CS, CallSiteRetTy);
+ createRetBitCast(CS, CallSiteRetTy, RetBitCast);
+
+ return CS.getInstruction();
}
Instruction *llvm::promoteCallWithIfThenElse(CallSite CS, Function *Callee,
// Version the indirect call site. If the called value is equal to the given
// callee, 'NewInst' will be executed, otherwise the original call site will
// be executed.
- BasicBlock *ThenBlock, *ElseBlock, *MergeBlock;
- Instruction *NewInst = versionCallSite(CS, Callee, BranchWeights, ThenBlock,
- ElseBlock, MergeBlock);
+ Instruction *NewInst = versionCallSite(CS, Callee, BranchWeights);
// Promote 'NewInst' so that it directly calls the desired function.
- Instruction *Cast = NewInst;
- promoteCall(CallSite(NewInst), Callee, Cast);
-
- // If the original call site is an invoke instruction, we have to fix-up phi
- // nodes in the invoke's normal and unwind destinations.
- if (auto *OrigInvoke = dyn_cast<InvokeInst>(CS.getInstruction())) {
- fixupPHINodeForNormalDest(OrigInvoke, MergeBlock, ElseBlock, Cast);
- fixupPHINodeForUnwindDest(OrigInvoke, MergeBlock, ThenBlock, ElseBlock);
- }
-
- // Create a phi node for the returned value of the call site.
- createRetPHINode(CS.getInstruction(), Cast ? Cast : NewInst);
-
- // Return the new direct call.
- return NewInst;
+ return promoteCall(CallSite(NewInst), Callee);
}
#undef DEBUG_TYPE