[llvm] r315272 - Renable r314928
Xinliang David Li via llvm-commits
llvm-commits at lists.llvm.org
Wed May 16 22:06:45 PDT 2018
Some kind of limit is probably needed. I can take a look at it if you do
not beat me to it.
David
On Wed, May 16, 2018 at 6:57 PM Mikhail Zolotukhin <mzolotukhin at apple.com>
wrote:
> Hi David,
>
> We found a huge compile time regression in an internal clang build caused
> by this change. I looked at the change and it seems that we’re scanning all
> phi-nodes in the basic block for every phi, which makes the algorithm
> quadratic. Of course, it’s not always the case, but as our build showed,
> it’s quite possible. How can we address it?
>
> Here is a simple script to expose the issue:
>
>
> Usage:
> > for i in `seq 4000 2000 20000`; do echo $i; python genphis.py $i | time
> opt -instcombine -o /dev/null; done
>
> 4000
> 0.20 real 0.16 user 0.00 sys
> 6000
> 0.37 real 0.32 user 0.00 sys
> 8000
> 0.98 real 0.92 user 0.01 sys
> 10000
> 2.65 real 2.58 user 0.01 sys
> 12000
> 3.79 real 3.71 user 0.02 sys
> 14000
> 5.08 real 4.99 user 0.02 sys
> 16000
> 6.80 real 6.71 user 0.03 sys
> 18000
> 8.41 real 8.31 user 0.03 sys
> 20000
> 10.43 real 10.31 user 0.04 sys
>
>
> Thanks,
> Michael
>
> On Oct 9, 2017, at 10:07 PM, Xinliang David Li via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
> Author: davidxl
> Date: Mon Oct 9 22:07:54 2017
> New Revision: 315272
>
> URL: http://llvm.org/viewvc/llvm-project?rev=315272&view=rev
> Log:
> Renable r314928
>
>
> Eliminate inttype phi with inttoptr/ptrtoint.
>
> This version fixed a bug in finding the matching
> phi -- the order of the incoming blocks may be
> different (triggered in self build on Windows).
> A new test case is added.
>
> Added:
> llvm/trunk/test/Transforms/InstCombine/intptr1.ll
> - copied unchanged from r315107,
> llvm/trunk/test/Transforms/InstCombine/intptr1.ll
> llvm/trunk/test/Transforms/InstCombine/intptr2.ll
> - copied unchanged from r315107,
> llvm/trunk/test/Transforms/InstCombine/intptr2.ll
> llvm/trunk/test/Transforms/InstCombine/intptr3.ll
> - copied unchanged from r315107,
> llvm/trunk/test/Transforms/InstCombine/intptr3.ll
> llvm/trunk/test/Transforms/InstCombine/intptr4.ll
> - copied unchanged from r315107,
> llvm/trunk/test/Transforms/InstCombine/intptr4.ll
> llvm/trunk/test/Transforms/InstCombine/intptr5.ll
> - copied unchanged from r315107,
> llvm/trunk/test/Transforms/InstCombine/intptr5.ll
> llvm/trunk/test/Transforms/InstCombine/intptr6.ll
> - copied unchanged from r315107,
> llvm/trunk/test/Transforms/InstCombine/intptr6.ll
> llvm/trunk/test/Transforms/InstCombine/intptr7.ll
> Modified:
> llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h
> llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp
>
> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h?rev=315272&r1=315271&r2=315272&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h (original)
> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h Mon Oct 9
> 22:07:54 2017
> @@ -670,6 +670,10 @@ private:
> Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
> Instruction *FoldPHIArgLoadIntoPHI(PHINode &PN);
> Instruction *FoldPHIArgZextsIntoPHI(PHINode &PN);
> + /// If an integer typed PHI has only one use which is an IntToPtr
> operation,
> + /// replace the PHI with an existing pointer typed PHI if it exists.
> Otherwise
> + /// insert a new pointer typed PHI and replace the original one.
> + Instruction *FoldIntegerTypedPHI(PHINode &PN);
>
> /// Helper function for FoldPHIArgXIntoPHI() to set debug location for
> the
> /// folded operation.
>
> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp?rev=315272&r1=315271&r2=315272&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp (original)
> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombinePHI.cpp Mon Oct 9
> 22:07:54 2017
> @@ -40,6 +40,238 @@ void InstCombiner::PHIArgMergedDebugLoc(
> }
> }
>
> +// Replace Integer typed PHI PN if the PHI's value is used as a pointer
> value.
> +// If there is an existing pointer typed PHI that produces the same value
> as PN,
> +// replace PN and the IntToPtr operation with it. Otherwise, synthesize a
> new
> +// PHI node:
> +//
> +// Case-1:
> +// bb1:
> +// int_init = PtrToInt(ptr_init)
> +// br label %bb2
> +// bb2:
> +// int_val = PHI([int_init, %bb1], [int_val_inc, %bb2]
> +// ptr_val = PHI([ptr_init, %bb1], [ptr_val_inc, %bb2]
> +// ptr_val2 = IntToPtr(int_val)
> +// ...
> +// use(ptr_val2)
> +// ptr_val_inc = ...
> +// inc_val_inc = PtrToInt(ptr_val_inc)
> +//
> +// ==>
> +// bb1:
> +// br label %bb2
> +// bb2:
> +// ptr_val = PHI([ptr_init, %bb1], [ptr_val_inc, %bb2]
> +// ...
> +// use(ptr_val)
> +// ptr_val_inc = ...
> +//
> +// Case-2:
> +// bb1:
> +// int_ptr = BitCast(ptr_ptr)
> +// int_init = Load(int_ptr)
> +// br label %bb2
> +// bb2:
> +// int_val = PHI([int_init, %bb1], [int_val_inc, %bb2]
> +// ptr_val2 = IntToPtr(int_val)
> +// ...
> +// use(ptr_val2)
> +// ptr_val_inc = ...
> +// inc_val_inc = PtrToInt(ptr_val_inc)
> +// ==>
> +// bb1:
> +// ptr_init = Load(ptr_ptr)
> +// br label %bb2
> +// bb2:
> +// ptr_val = PHI([ptr_init, %bb1], [ptr_val_inc, %bb2]
> +// ...
> +// use(ptr_val)
> +// ptr_val_inc = ...
> +// ...
> +//
> +Instruction *InstCombiner::FoldIntegerTypedPHI(PHINode &PN) {
> + if (!PN.getType()->isIntegerTy())
> + return nullptr;
> + if (!PN.hasOneUse())
> + return nullptr;
> +
> + auto *IntToPtr = dyn_cast<IntToPtrInst>(PN.user_back());
> + if (!IntToPtr)
> + return nullptr;
> +
> + // Check if the pointer is actually used as pointer:
> + auto HasPointerUse = [](Instruction *IIP) {
> + for (User *U : IIP->users()) {
> + Value *Ptr = nullptr;
> + if (LoadInst *LoadI = dyn_cast<LoadInst>(U)) {
> + Ptr = LoadI->getPointerOperand();
> + } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
> + Ptr = SI->getPointerOperand();
> + } else if (GetElementPtrInst *GI = dyn_cast<GetElementPtrInst>(U)) {
> + Ptr = GI->getPointerOperand();
> + }
> +
> + if (Ptr && Ptr == IIP)
> + return true;
> + }
> + return false;
> + };
> +
> + if (!HasPointerUse(IntToPtr))
> + return nullptr;
> +
> + if (DL.getPointerSizeInBits(IntToPtr->getAddressSpace()) !=
> + DL.getTypeSizeInBits(IntToPtr->getOperand(0)->getType()))
> + return nullptr;
> +
> + SmallVector<Value *, 4> AvailablePtrVals;
> + for (unsigned i = 0; i != PN.getNumIncomingValues(); ++i) {
> + Value *Arg = PN.getIncomingValue(i);
> +
> + // First look backward:
> + if (auto *PI = dyn_cast<PtrToIntInst>(Arg)) {
> + AvailablePtrVals.emplace_back(PI->getOperand(0));
> + continue;
> + }
> +
> + // Next look forward:
> + Value *ArgIntToPtr = nullptr;
> + for (User *U : Arg->users()) {
> + if (isa<IntToPtrInst>(U) && U->getType() == IntToPtr->getType() &&
> + (DT.dominates(cast<Instruction>(U), PN.getIncomingBlock(i)) ||
> + cast<Instruction>(U)->getParent() == PN.getIncomingBlock(i))) {
> + ArgIntToPtr = U;
> + break;
> + }
> + }
> +
> + if (ArgIntToPtr) {
> + AvailablePtrVals.emplace_back(ArgIntToPtr);
> + continue;
> + }
> +
> + // If Arg is defined by a PHI, allow it. This will also create
> + // more opportunities iteratively.
> + if (isa<PHINode>(Arg)) {
> + AvailablePtrVals.emplace_back(Arg);
> + continue;
> + }
> +
> + // For a single use integer load:
> + auto *LoadI = dyn_cast<LoadInst>(Arg);
> + if (!LoadI)
> + return nullptr;
> +
> + if (!LoadI->hasOneUse())
> + return nullptr;
> +
> + // Push the integer typed Load instruction into the available
> + // value set, and fix it up later when the pointer typed PHI
> + // is synthesized.
> + AvailablePtrVals.emplace_back(LoadI);
> + }
> +
> + // Now search for a matching PHI
> + auto *BB = PN.getParent();
> + assert(AvailablePtrVals.size() == PN.getNumIncomingValues() &&
> + "Not enough available ptr typed incoming values");
> + PHINode *MatchingPtrPHI = nullptr;
> + for (auto II = BB->begin(), EI =
> BasicBlock::iterator(BB->getFirstNonPHI());
> + II != EI; II++) {
> + PHINode *PtrPHI = dyn_cast<PHINode>(II);
> + if (!PtrPHI || PtrPHI == &PN || PtrPHI->getType() !=
> IntToPtr->getType())
> + continue;
> + MatchingPtrPHI = PtrPHI;
> + for (unsigned i = 0; i != PtrPHI->getNumIncomingValues(); ++i) {
> + if (AvailablePtrVals[i] !=
> + PtrPHI->getIncomingValueForBlock(PN.getIncomingBlock(i))) {
> + MatchingPtrPHI = nullptr;
> + break;
> + }
> + }
> +
> + if (MatchingPtrPHI)
> + break;
> + }
> +
> + if (MatchingPtrPHI) {
> + assert(MatchingPtrPHI->getType() == IntToPtr->getType() &&
> + "Phi's Type does not match with IntToPtr");
> + // The PtrToCast + IntToPtr will be simplified later
> + return CastInst::CreateBitOrPointerCast(MatchingPtrPHI,
> +
> IntToPtr->getOperand(0)->getType());
> + }
> +
> + // If it requires a conversion for every PHI operand, do not do it.
> + if (std::all_of(AvailablePtrVals.begin(), AvailablePtrVals.end(),
> + [&](Value *V) {
> + return (V->getType() != IntToPtr->getType()) ||
> + isa<IntToPtrInst>(V);
> + }))
> + return nullptr;
> +
> + // If any of the operand that requires casting is a terminator
> + // instruction, do not do it.
> + if (std::any_of(AvailablePtrVals.begin(), AvailablePtrVals.end(),
> + [&](Value *V) {
> + return (V->getType() != IntToPtr->getType()) &&
> + isa<TerminatorInst>(V);
> + }))
> + return nullptr;
> +
> + PHINode *NewPtrPHI = PHINode::Create(
> + IntToPtr->getType(), PN.getNumIncomingValues(), PN.getName() +
> ".ptr");
> +
> + InsertNewInstBefore(NewPtrPHI, PN);
> + SmallDenseMap<Value *, Instruction *> Casts;
> + for (unsigned i = 0; i != PN.getNumIncomingValues(); ++i) {
> + auto *IncomingBB = PN.getIncomingBlock(i);
> + auto *IncomingVal = AvailablePtrVals[i];
> +
> + if (IncomingVal->getType() == IntToPtr->getType()) {
> + NewPtrPHI->addIncoming(IncomingVal, IncomingBB);
> + continue;
> + }
> +
> +#ifndef NDEBUG
> + LoadInst *LoadI = dyn_cast<LoadInst>(IncomingVal);
> + assert((isa<PHINode>(IncomingVal) ||
> + IncomingVal->getType()->isPointerTy() ||
> + (LoadI && LoadI->hasOneUse())) &&
> + "Can not replace LoadInst with multiple uses");
> +#endif
> + // Need to insert a BitCast.
> + // For an integer Load instruction with a single use, the load +
> IntToPtr
> + // cast will be simplified into a pointer load:
> + // %v = load i64, i64* %a.ip, align 8
> + // %v.cast = inttoptr i64 %v to float **
> + // ==>
> + // %v.ptrp = bitcast i64 * %a.ip to float **
> + // %v.cast = load float *, float ** %v.ptrp, align 8
> + Instruction *&CI = Casts[IncomingVal];
> + if (!CI) {
> + CI = CastInst::CreateBitOrPointerCast(IncomingVal,
> IntToPtr->getType(),
> + IncomingVal->getName() +
> ".ptr");
> + if (auto *IncomingI = dyn_cast<Instruction>(IncomingVal)) {
> + BasicBlock::iterator InsertPos(IncomingI);
> + InsertPos++;
> + if (isa<PHINode>(IncomingI))
> + InsertPos = IncomingI->getParent()->getFirstInsertionPt();
> + InsertNewInstBefore(CI, *InsertPos);
> + } else {
> + auto *InsertBB = &IncomingBB->getParent()->getEntryBlock();
> + InsertNewInstBefore(CI, *InsertBB->getFirstInsertionPt());
> + }
> + }
> + NewPtrPHI->addIncoming(CI, IncomingBB);
> + }
> +
> + // The PtrToCast + IntToPtr will be simplified later
> + return CastInst::CreateBitOrPointerCast(NewPtrPHI,
> +
> IntToPtr->getOperand(0)->getType());
> +}
> +
> /// If we have something like phi [add (a,b), add(a,c)] and if a/b/c and
> the
> /// adds all have a single use, turn this into a phi and a single binop.
> Instruction *InstCombiner::FoldPHIArgBinOpIntoPHI(PHINode &PN) {
> @@ -903,6 +1135,9 @@ Instruction *InstCombiner::visitPHINode(
> // this PHI only has a single use (a PHI), and if that PHI only has one
> use (a
> // PHI)... break the cycle.
> if (PN.hasOneUse()) {
> + if (Instruction *Result = FoldIntegerTypedPHI(PN))
> + return Result;
> +
> Instruction *PHIUser = cast<Instruction>(PN.user_back());
> if (PHINode *PU = dyn_cast<PHINode>(PHIUser)) {
> SmallPtrSet<PHINode*, 16> PotentiallyDeadPHIs;
>
> Added: llvm/trunk/test/Transforms/InstCombine/intptr7.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/intptr7.ll?rev=315272&view=auto
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/intptr7.ll (added)
> +++ llvm/trunk/test/Transforms/InstCombine/intptr7.ll Mon Oct 9 22:07:54
> 2017
> @@ -0,0 +1,58 @@
> +; RUN: opt < %s -instcombine -S | FileCheck %s
> +
> +define void @matching_phi(i64 %a, float* %b, i1 %cond) {
> +; CHECK-LABEL: @matching_phi
> +entry:
> + %cmp1 = icmp eq i1 %cond, 0
> + %add.int = add i64 %a, 1
> + %add = inttoptr i64 %add.int to float *
> +
> + %addb = getelementptr inbounds float, float* %b, i64 2
> + %addb.int = ptrtoint float* %addb to i64
> + br i1 %cmp1, label %A, label %B
> +A:
> + br label %C
> +B:
> + store float 1.0e+01, float* %add, align 4
> + br label %C
> +
> +C:
> + %a.addr.03 = phi float* [ %addb, %A ], [ %add, %B ]
> + %b.addr.02 = phi i64 [ %addb.int, %A ], [ %add.int, %B ]
> + %tmp = inttoptr i64 %b.addr.02 to float*
> +; CHECK: %a.addr.03 = phi
> +; CHECK-NEXT: = load
> + %tmp1 = load float, float* %tmp, align 4
> + %mul.i = fmul float %tmp1, 4.200000e+01
> + store float %mul.i, float* %a.addr.03, align 4
> + ret void
> +}
> +
> +define void @no_matching_phi(i64 %a, float* %b, i1 %cond) {
> +; CHECK-LABEL: @no_matching_phi
> +entry:
> + %cmp1 = icmp eq i1 %cond, 0
> + %add.int = add i64 %a, 1
> + %add = inttoptr i64 %add.int to float *
> +
> + %addb = getelementptr inbounds float, float* %b, i64 2
> + %addb.int = ptrtoint float* %addb to i64
> + br i1 %cmp1, label %A, label %B
> +A:
> + br label %C
> +B:
> + store float 1.0e+01, float* %add, align 4
> + br label %C
> +
> +C:
> + %a.addr.03 = phi float* [ %addb, %A ], [ %add, %B ]
> + %b.addr.02 = phi i64 [ %addb.int, %B ], [ %add.int, %A ]
> + %tmp = inttoptr i64 %b.addr.02 to float*
> + %tmp1 = load float, float* %tmp, align 4
> +; CHECK: %a.addr.03 = phi
> +; CHECK-NEXT: %b.addr.02.ptr = phi
> +; CHECK-NEXT: = load
> + %mul.i = fmul float %tmp1, 4.200000e+01
> + store float %mul.i, float* %a.addr.03, align 4
> + ret void
> +}
>
>
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