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+//===- CallPromotionUtils.cpp - Utilities for call promotion ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements utilities useful for promoting indirect call sites to
+// direct call sites.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/CallPromotionUtils.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "call-promotion-utils"
+
+/// Fix-up phi nodes in an invoke instruction's normal destination.
+///
+/// After versioning an invoke instruction, values coming from the original
+/// 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 *MergeBlock) {
+ for (PHINode &Phi : Invoke->getNormalDest()->phis()) {
+ int Idx = Phi.getBasicBlockIndex(OrigBlock);
+ if (Idx == -1)
+ continue;
+ Phi.setIncomingBlock(Idx, MergeBlock);
+ }
+}
+
+/// Fix-up phi nodes in an invoke instruction's unwind destination.
+///
+/// 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) {
+ for (PHINode &Phi : Invoke->getUnwindDest()->phis()) {
+ int Idx = Phi.getBasicBlockIndex(OrigBlock);
+ if (Idx == -1)
+ continue;
+ auto *V = Phi.getIncomingValue(Idx);
+ Phi.setIncomingBlock(Idx, ThenBlock);
+ Phi.addIncoming(V, ElseBlock);
+ }
+}
+
+/// 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.
+///
+/// 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;
+
+ Builder.SetInsertPoint(&MergeBlock->front());
+ PHINode *Phi = Builder.CreatePHI(OrigInst->getType(), 0);
+ SmallVector<User *, 16> UsersToUpdate;
+ for (User *U : OrigInst->users())
+ UsersToUpdate.push_back(U);
+ for (User *U : UsersToUpdate)
+ U->replaceUsesOfWith(OrigInst, Phi);
+ Phi->addIncoming(OrigInst, OrigInst->getParent());
+ Phi->addIncoming(NewInst, NewInst->getParent());
+}
+
+/// Cast a call or invoke instruction to the given type.
+///
+/// When promoting a call site, the return type of the call site might not match
+/// 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.
+///
+/// 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.
+ SmallVector<User *, 16> UsersToUpdate;
+ for (User *U : CS.getInstruction()->users())
+ UsersToUpdate.push_back(U);
+
+ // Determine an appropriate location to create the bitcast for the return
+ // 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 =
+ &SplitEdge(Invoke->getParent(), Invoke->getNormalDest())->front();
+ else
+ InsertBefore = &*std::next(CS.getInstruction()->getIterator());
+
+ // Bitcast the return value to the correct type.
+ auto *Cast = CastInst::CreateBitOrPointerCast(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);
+}
+
+/// Predicate and clone the given call site.
+///
+/// This function creates an if-then-else structure at the location of the call
+/// site. The "if" condition compares the call site's called value to the given
+/// 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) {
+
+ 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.
+ 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
+ // "then" block.
+ Instruction *ThenTerm = nullptr;
+ Instruction *ElseTerm = nullptr;
+ SplitBlockAndInsertIfThenElse(Cond, CS.getInstruction(), &ThenTerm, &ElseTerm,
+ BranchWeights);
+ BasicBlock *ThenBlock = ThenTerm->getParent();
+ BasicBlock *ElseBlock = ElseTerm->getParent();
+ BasicBlock *MergeBlock = OrigInst->getParent();
+
+ ThenBlock->setName("if.true.direct_targ");
+ ElseBlock->setName("if.false.orig_indirect");
+ MergeBlock->setName("if.end.icp");
+
+ Instruction *NewInst = OrigInst->clone();
+ OrigInst->moveBefore(ElseTerm);
+ NewInst->insertBefore(ThenTerm);
+
+ // If the original call site is an invoke instruction, we have extra work to
+ // 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);
+
+ // Invoke instructions are terminating, so we don't need the terminator
+ // instructions that were just created.
+ ThenTerm->eraseFromParent();
+ ElseTerm->eraseFromParent();
+
+ // Branch from the "merge" block to the original normal destination.
+ Builder.SetInsertPoint(MergeBlock);
+ Builder.CreateBr(OrigInvoke->getNormalDest());
+
+ // 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;
+}
+
+bool llvm::isLegalToPromote(CallSite CS, Function *Callee,
+ const char **FailureReason) {
+ assert(!CS.getCalledFunction() && "Only indirect call sites can be promoted");
+
+ auto &DL = Callee->getParent()->getDataLayout();
+
+ // Check the return type. The callee's return value type must be bitcast
+ // compatible with the call site's type.
+ Type *CallRetTy = CS.getInstruction()->getType();
+ Type *FuncRetTy = Callee->getReturnType();
+ if (CallRetTy != FuncRetTy)
+ if (!CastInst::isBitOrNoopPointerCastable(FuncRetTy, CallRetTy, DL)) {
+ if (FailureReason)
+ *FailureReason = "Return type mismatch";
+ return false;
+ }
+
+ // The number of formal arguments of the callee.
+ unsigned NumParams = Callee->getFunctionType()->getNumParams();
+
+ // Check the number of arguments. The callee and call site must agree on the
+ // number of arguments.
+ if (CS.arg_size() != NumParams && !Callee->isVarArg()) {
+ if (FailureReason)
+ *FailureReason = "The number of arguments mismatch";
+ return false;
+ }
+
+ // Check the argument types. The callee's formal argument types must be
+ // bitcast compatible with the corresponding actual argument types of the call
+ // site.
+ for (unsigned I = 0; I < NumParams; ++I) {
+ Type *FormalTy = Callee->getFunctionType()->getFunctionParamType(I);
+ Type *ActualTy = CS.getArgument(I)->getType();
+ if (FormalTy == ActualTy)
+ continue;
+ if (!CastInst::isBitOrNoopPointerCastable(ActualTy, FormalTy, DL)) {
+ if (FailureReason)
+ *FailureReason = "Argument type mismatch";
+ return false;
+ }
+ }
+
+ return true;
+}
+
+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 (but don't
+ // change the type).
+ cast<CallBase>(CS.getInstruction())->setCalledOperand(Callee);
+
+ // Since the call site will no longer be direct, we must clear metadata that
+ // is only appropriate for indirect calls. This includes !prof and !callees
+ // metadata.
+ CS.getInstruction()->setMetadata(LLVMContext::MD_prof, nullptr);
+ CS.getInstruction()->setMetadata(LLVMContext::MD_callees, nullptr);
+
+ // If the function type of the call site matches that of the callee, no
+ // additional work is required.
+ if (CS.getFunctionType() == Callee->getFunctionType())
+ return CS.getInstruction();
+
+ // Save the return types of the call site and callee.
+ Type *CallSiteRetTy = CS.getInstruction()->getType();
+ Type *CalleeRetTy = Callee->getReturnType();
+
+ // Change the function type of the call site the match that of the callee.
+ CS.mutateFunctionType(Callee->getFunctionType());
+
+ // Inspect the arguments of the call site. If an argument's type doesn't
+ // match the corresponding formal argument's type in the callee, bitcast it
+ // to the correct type.
+ auto CalleeType = Callee->getFunctionType();
+ auto CalleeParamNum = CalleeType->getNumParams();
+
+ LLVMContext &Ctx = Callee->getContext();
+ const AttributeList &CallerPAL = CS.getAttributes();
+ // The new list of argument attributes.
+ SmallVector<AttributeSet, 4> NewArgAttrs;
+ bool AttributeChanged = false;
+
+ for (unsigned ArgNo = 0; ArgNo < CalleeParamNum; ++ArgNo) {
+ auto *Arg = CS.getArgument(ArgNo);
+ Type *FormalTy = CalleeType->getParamType(ArgNo);
+ Type *ActualTy = Arg->getType();
+ if (FormalTy != ActualTy) {
+ auto *Cast = CastInst::CreateBitOrPointerCast(Arg, FormalTy, "",
+ CS.getInstruction());
+ CS.setArgument(ArgNo, Cast);
+
+ // Remove any incompatible attributes for the argument.
+ AttrBuilder ArgAttrs(CallerPAL.getParamAttributes(ArgNo));
+ ArgAttrs.remove(AttributeFuncs::typeIncompatible(FormalTy));
+
+ // If byval is used, this must be a pointer type, and the byval type must
+ // match the element type. Update it if present.
+ if (ArgAttrs.getByValType()) {
+ Type *NewTy = Callee->getParamByValType(ArgNo);
+ ArgAttrs.addByValAttr(
+ NewTy ? NewTy : cast<PointerType>(FormalTy)->getElementType());
+ }
+
+ NewArgAttrs.push_back(AttributeSet::get(Ctx, ArgAttrs));
+ AttributeChanged = true;
+ } else
+ NewArgAttrs.push_back(CallerPAL.getParamAttributes(ArgNo));
+ }
+
+ // If the return type of the call site doesn't match that of the callee, cast
+ // the returned value to the appropriate type.
+ // Remove any incompatible return value attribute.
+ AttrBuilder RAttrs(CallerPAL, AttributeList::ReturnIndex);
+ if (!CallSiteRetTy->isVoidTy() && CallSiteRetTy != CalleeRetTy) {
+ createRetBitCast(CS, CallSiteRetTy, RetBitCast);
+ RAttrs.remove(AttributeFuncs::typeIncompatible(CalleeRetTy));
+ AttributeChanged = true;
+ }
+
+ // Set the new callsite attribute.
+ if (AttributeChanged)
+ CS.setAttributes(AttributeList::get(Ctx, CallerPAL.getFnAttributes(),
+ AttributeSet::get(Ctx, RAttrs),
+ NewArgAttrs));
+
+ return CS.getInstruction();
+}
+
+Instruction *llvm::promoteCallWithIfThenElse(CallSite CS, Function *Callee,
+ MDNode *BranchWeights) {
+
+ // 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.
+ Instruction *NewInst = versionCallSite(CS, Callee, BranchWeights);
+
+ // Promote 'NewInst' so that it directly calls the desired function.
+ return promoteCall(CallSite(NewInst), Callee);
+}
+
+#undef DEBUG_TYPE
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