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[CallSiteSplitting] Pass list of (BB, Conditions) pairs to splitCallS…
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…ite.

This removes some duplication from splitCallSite and makes it easier to
add additional code dealing with each predecessor. It also allows us to
split for more than 2 predecessors, although that is not enabled for
now.

Reviewers: junbuml, mcrosier, davidxl, davide

Reviewed By: junbuml

Differential Revision: https://reviews.llvm.org/D41858

llvm-svn: 322599
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@fhahn
fhahn committed Jan 16, 2018
1 parent 3c66e2c commit c6c89bf
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Showing 5 changed files with 163 additions and 168 deletions.
147 changes: 71 additions & 76 deletions llvm/lib/Transforms/Scalar/CallSiteSplitting.cpp
View file
Expand Up @@ -73,9 +73,7 @@ using namespace PatternMatch;

STATISTIC(NumCallSiteSplit, "Number of call-site split");

static void addNonNullAttribute(Instruction *CallI, Instruction *NewCallI,
Value *Op) {
CallSite CS(NewCallI);
static void addNonNullAttribute(CallSite CS, Value *Op) {
unsigned ArgNo = 0;
for (auto &I : CS.args()) {
if (&*I == Op)
Expand All @@ -84,9 +82,8 @@ static void addNonNullAttribute(Instruction *CallI, Instruction *NewCallI,
}
}

static void setConstantInArgument(Instruction *CallI, Instruction *NewCallI,
Value *Op, Constant *ConstValue) {
CallSite CS(NewCallI);
static void setConstantInArgument(CallSite CS, Value *Op,
Constant *ConstValue) {
unsigned ArgNo = 0;
for (auto &I : CS.args()) {
if (&*I == Op)
Expand All @@ -111,11 +108,13 @@ static bool isCondRelevantToAnyCallArgument(ICmpInst *Cmp, CallSite CS) {
return false;
}

typedef std::pair<ICmpInst *, unsigned> ConditionTy;
typedef SmallVector<ConditionTy, 2> ConditionsTy;

/// If From has a conditional jump to To, add the condition to Conditions,
/// if it is relevant to any argument at CS.
static void
recordCondition(const CallSite &CS, BasicBlock *From, BasicBlock *To,
SmallVectorImpl<std::pair<ICmpInst *, unsigned>> &Conditions) {
static void recordCondition(CallSite CS, BasicBlock *From, BasicBlock *To,
ConditionsTy &Conditions) {
auto *BI = dyn_cast<BranchInst>(From->getTerminator());
if (!BI || !BI->isConditional())
return;
Expand All @@ -136,9 +135,8 @@ recordCondition(const CallSite &CS, BasicBlock *From, BasicBlock *To,
/// Record ICmp conditions relevant to any argument in CS following Pred's
/// single successors. If there are conflicting conditions along a path, like
/// x == 1 and x == 0, the first condition will be used.
static void
recordConditions(const CallSite &CS, BasicBlock *Pred,
SmallVectorImpl<std::pair<ICmpInst *, unsigned>> &Conditions) {
static void recordConditions(CallSite CS, BasicBlock *Pred,
ConditionsTy &Conditions) {
recordCondition(CS, Pred, CS.getInstruction()->getParent(), Conditions);
BasicBlock *From = Pred;
BasicBlock *To = Pred;
Expand All @@ -150,24 +148,17 @@ recordConditions(const CallSite &CS, BasicBlock *Pred,
}
}

static Instruction *
addConditions(CallSite &CS,
SmallVectorImpl<std::pair<ICmpInst *, unsigned>> &Conditions) {
if (Conditions.empty())
return nullptr;

Instruction *NewCI = CS.getInstruction()->clone();
static void addConditions(CallSite CS, const ConditionsTy &Conditions) {
for (auto &Cond : Conditions) {
Value *Arg = Cond.first->getOperand(0);
Constant *ConstVal = cast<Constant>(Cond.first->getOperand(1));
if (Cond.second == ICmpInst::ICMP_EQ)
setConstantInArgument(CS.getInstruction(), NewCI, Arg, ConstVal);
setConstantInArgument(CS, Arg, ConstVal);
else if (ConstVal->getType()->isPointerTy() && ConstVal->isNullValue()) {
assert(Cond.second == ICmpInst::ICMP_NE);
addNonNullAttribute(CS.getInstruction(), NewCI, Arg);
addNonNullAttribute(CS, Arg);
}
}
return NewCI;
}

static SmallVector<BasicBlock *, 2> getTwoPredecessors(BasicBlock *BB) {
Expand Down Expand Up @@ -200,14 +191,17 @@ static bool canSplitCallSite(CallSite CS) {
return CallSiteBB->canSplitPredecessors();
}

/// Return true if the CS is split into its new predecessors which are directly
/// hooked to each of its original predecessors pointed by PredBB1 and PredBB2.
/// CallInst1 and CallInst2 will be the new call-sites placed in the new
/// predecessors split for PredBB1 and PredBB2, respectively.
/// Return true if the CS is split into its new predecessors.
///
/// For each (predecessor, conditions from predecessors) pair, it will split the
/// basic block containing the call site, hook it up to the predecessor and
/// replace the call instruction with new call instructions, which contain
/// constraints based on the conditions from their predecessors.
/// For example, in the IR below with an OR condition, the call-site can
/// be split. Assuming PredBB1=Header and PredBB2=TBB, CallInst1 will be the
/// call-site placed between Header and Tail, and CallInst2 will be the
/// call-site between TBB and Tail.
/// be split. In this case, Preds for Tail is [(Header, a == null),
/// (TBB, a != null, b == null)]. Tail is replaced by 2 split blocks, containing
/// CallInst1, which has constraints based on the conditions from Head and
/// CallInst2, which has constraints based on the conditions coming from TBB.
///
/// From :
///
Expand Down Expand Up @@ -240,55 +234,50 @@ static bool canSplitCallSite(CallSite CS) {
/// Note that in case any arguments at the call-site are constrained by its
/// predecessors, new call-sites with more constrained arguments will be
/// created in createCallSitesOnPredicatedArgument().
static void splitCallSite(CallSite CS, BasicBlock *PredBB1, BasicBlock *PredBB2,
Instruction *CallInst1, Instruction *CallInst2) {
static void splitCallSite(
CallSite CS,
const SmallVectorImpl<std::pair<BasicBlock *, ConditionsTy>> &Preds) {
Instruction *Instr = CS.getInstruction();
BasicBlock *TailBB = Instr->getParent();
assert(Instr == (TailBB->getFirstNonPHIOrDbg()) && "Unexpected call-site");

BasicBlock *SplitBlock1 =
SplitBlockPredecessors(TailBB, PredBB1, ".predBB1.split");
BasicBlock *SplitBlock2 =
SplitBlockPredecessors(TailBB, PredBB2, ".predBB2.split");

assert((SplitBlock1 && SplitBlock2) && "Unexpected new basic block split.");

if (!CallInst1)
CallInst1 = Instr->clone();
if (!CallInst2)
CallInst2 = Instr->clone();

CallInst1->insertBefore(&*SplitBlock1->getFirstInsertionPt());
CallInst2->insertBefore(&*SplitBlock2->getFirstInsertionPt());
PHINode *CallPN = nullptr;
if (Instr->getNumUses())
CallPN = PHINode::Create(Instr->getType(), Preds.size(), "phi.call");

CallSite CS1(CallInst1);
CallSite CS2(CallInst2);

// Handle PHIs used as arguments in the call-site.
for (PHINode &PN : TailBB->phis()) {
unsigned ArgNo = 0;
for (auto &CI : CS.args()) {
if (&*CI == &PN) {
CS1.setArgument(ArgNo, PN.getIncomingValueForBlock(SplitBlock1));
CS2.setArgument(ArgNo, PN.getIncomingValueForBlock(SplitBlock2));
DEBUG(dbgs() << "split call-site : " << *Instr << " into \n");
for (const auto &P : Preds) {
BasicBlock *PredBB = P.first;
BasicBlock *SplitBlock =
SplitBlockPredecessors(TailBB, PredBB, ".predBB.split");
assert(SplitBlock && "Unexpected new basic block split.");

Instruction *NewCI = Instr->clone();
CallSite NewCS(NewCI);
addConditions(NewCS, P.second);
NewCI->insertBefore(&*SplitBlock->getFirstInsertionPt());

// Handle PHIs used as arguments in the call-site.
for (PHINode &PN : TailBB->phis()) {
unsigned ArgNo = 0;
for (auto &CI : CS.args()) {
if (&*CI == &PN) {
NewCS.setArgument(ArgNo, PN.getIncomingValueForBlock(SplitBlock));
}
++ArgNo;
}
++ArgNo;
}
DEBUG(dbgs() << " " << *NewCI << " in " << SplitBlock->getName()
<< "\n");
if (CallPN)
CallPN->addIncoming(NewCI, SplitBlock);
}

// Replace users of the original call with a PHI mering call-sites split.
if (Instr->getNumUses()) {
PHINode *PN = PHINode::Create(Instr->getType(), 2, "phi.call",
TailBB->getFirstNonPHI());
PN->addIncoming(CallInst1, SplitBlock1);
PN->addIncoming(CallInst2, SplitBlock2);
Instr->replaceAllUsesWith(PN);
if (CallPN) {
CallPN->insertBefore(TailBB->getFirstNonPHI());
Instr->replaceAllUsesWith(CallPN);
}
DEBUG(dbgs() << "split call-site : " << *Instr << " into \n");
DEBUG(dbgs() << " " << *CallInst1 << " in " << SplitBlock1->getName()
<< "\n");
DEBUG(dbgs() << " " << *CallInst2 << " in " << SplitBlock2->getName()
<< "\n");

Instr->eraseFromParent();
NumCallSiteSplit++;
}
Expand Down Expand Up @@ -326,7 +315,9 @@ static bool tryToSplitOnPHIPredicatedArgument(CallSite CS) {
return false;

auto Preds = getTwoPredecessors(CS.getInstruction()->getParent());
splitCallSite(CS, Preds[0], Preds[1], nullptr, nullptr);
SmallVector<std::pair<BasicBlock *, ConditionsTy>, 2> PredsCS = {
{Preds[0], {}}, {Preds[1], {}}};
splitCallSite(CS, PredsCS);
return true;
}

Expand All @@ -335,16 +326,20 @@ static bool tryToSplitOnPredicatedArgument(CallSite CS) {
if (Preds[0] == Preds[1])
return false;

SmallVector<std::pair<ICmpInst *, unsigned>, 2> C1, C2;
recordConditions(CS, Preds[0], C1);
recordConditions(CS, Preds[1], C2);
SmallVector<std::pair<BasicBlock *, ConditionsTy>, 2> PredsCS;
for (auto *Pred : make_range(Preds.rbegin(), Preds.rend())) {
ConditionsTy Conditions;
recordConditions(CS, Pred, Conditions);
PredsCS.push_back({Pred, Conditions});
}

Instruction *CallInst1 = addConditions(CS, C1);
Instruction *CallInst2 = addConditions(CS, C2);
if (!CallInst1 && !CallInst2)
if (std::all_of(PredsCS.begin(), PredsCS.end(),
[](const std::pair<BasicBlock *, ConditionsTy> &P) {
return P.second.empty();
}))
return false;

splitCallSite(CS, Preds[1], Preds[0], CallInst2, CallInst1);
splitCallSite(CS, PredsCS);
return true;
}

Expand Down
40 changes: 20 additions & 20 deletions llvm/test/Transforms/CallSiteSplitting/callsite-no-or-structure.ll
View file
Expand Up @@ -3,15 +3,15 @@

; CHECK-LABEL: @test_simple
; CHECK-LABEL: Header:
; CHECK-NEXT: br i1 undef, label %Tail.predBB1.split
; CHECK-NEXT: br i1 undef, label %Tail.predBB.split
; CHECK-LABEL: TBB:
; CHECK: br i1 %cmp, label %Tail.predBB2.split
; CHECK-LABEL: Tail.predBB1.split:
; CHECK: br i1 %cmp, label %Tail.predBB.split1
; CHECK-LABEL: Tail.predBB.split:
; CHECK: %[[CALL1:.*]] = call i32 @callee(i32* %a, i32 %v, i32 %p)
; CHECK-LABEL: Tail.predBB2.split:
; CHECK-LABEL: Tail.predBB.split1:
; CHECK: %[[CALL2:.*]] = call i32 @callee(i32* null, i32 %v, i32 %p)
; CHECK-LABEL: Tail
; CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB1.split ], [ %[[CALL2]], %Tail.predBB2.split ]
; CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB.split ], [ %[[CALL2]], %Tail.predBB.split1 ]
; CHECK: ret i32 %[[MERGED]]
define i32 @test_simple(i32* %a, i32 %v, i32 %p) {
Header:
Expand All @@ -31,15 +31,15 @@ End:

; CHECK-LABEL: @test_eq_eq_eq_untaken
; CHECK-LABEL: Header:
; CHECK: br i1 %tobool1, label %TBB1, label %Tail.predBB1.split
; CHECK: br i1 %tobool1, label %TBB1, label %Tail.predBB.split
; CHECK-LABEL: TBB2:
; CHECK: br i1 %cmp2, label %Tail.predBB2.split, label %End
; CHECK-LABEL: Tail.predBB1.split:
; CHECK: br i1 %cmp2, label %Tail.predBB.split1, label %End
; CHECK-LABEL: Tail.predBB.split:
; CHECK: %[[CALL1:.*]] = call i32 @callee(i32* nonnull %a, i32 %v, i32 %p)
; CHECK-LABEL: Tail.predBB2.split:
; CHECK-LABEL: Tail.predBB.split1:
; CHECK: %[[CALL2:.*]] = call i32 @callee(i32* null, i32 1, i32 99)
; CHECK-LABEL: Tail
; CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB1.split ], [ %[[CALL2]], %Tail.predBB2.split ]
; CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB.split ], [ %[[CALL2]], %Tail.predBB.split1 ]
; CHECK: ret i32 %[[MERGED]]
define i32 @test_eq_eq_eq_untaken2(i32* %a, i32 %v, i32 %p) {
Header:
Expand All @@ -64,15 +64,15 @@ End:

; CHECK-LABEL: @test_eq_ne_eq_untaken
; CHECK-LABEL: Header:
; CHECK: br i1 %tobool1, label %TBB1, label %Tail.predBB1.split
; CHECK: br i1 %tobool1, label %TBB1, label %Tail.predBB.split
; CHECK-LABEL: TBB2:
; CHECK: br i1 %cmp2, label %Tail.predBB2.split, label %End
; CHECK-LABEL: Tail.predBB1.split:
; CHECK: br i1 %cmp2, label %Tail.predBB.split1, label %End
; CHECK-LABEL: Tail.predBB.split:
; CHECK: %[[CALL1:.*]] = call i32 @callee(i32* nonnull %a, i32 %v, i32 %p)
; CHECK-LABEL: Tail.predBB2.split:
; CHECK-LABEL: Tail.predBB.split1:
; CHECK: %[[CALL2:.*]] = call i32 @callee(i32* null, i32 %v, i32 99)
; CHECK-LABEL: Tail
; CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB1.split ], [ %[[CALL2]], %Tail.predBB2.split ]
; CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB.split ], [ %[[CALL2]], %Tail.predBB.split1 ]
; CHECK: ret i32 %[[MERGED]]
define i32 @test_eq_ne_eq_untaken(i32* %a, i32 %v, i32 %p) {
Header:
Expand All @@ -97,17 +97,17 @@ End:

; CHECK-LABEL: @test_header_header2_tbb
; CHECK: Header2:
; CHECK:br i1 %tobool2, label %Tail.predBB1.split, label %TBB1
; CHECK:br i1 %tobool2, label %Tail.predBB.split, label %TBB1
; CHECK-LABEL: TBB2:
; CHECK: br i1 %cmp2, label %Tail.predBB2.split, label %End
; CHECK-LABEL: Tail.predBB1.split:
; CHECK: br i1 %cmp2, label %Tail.predBB.split1, label %End
; CHECK-LABEL: Tail.predBB.split:
; CHECK: %[[CALL1:.*]] = call i32 @callee(i32* nonnull %a, i32 %v, i32 10)
; CHECK-LABEL: Tail.predBB2.split:
; CHECK-LABEL: Tail.predBB.split1:
; NOTE: CallSiteSplitting cannot infer that %a is null here, as it currently
; only supports recording conditions along a single predecessor path.
; CHECK: %[[CALL2:.*]] = call i32 @callee(i32* %a, i32 1, i32 99)
; CHECK-LABEL: Tail
; CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB1.split ], [ %[[CALL2]], %Tail.predBB2.split ]
; CHECK: %[[MERGED:.*]] = phi i32 [ %[[CALL1]], %Tail.predBB.split ], [ %[[CALL2]], %Tail.predBB.split1 ]
; CHECK: ret i32 %[[MERGED]]
define i32 @test_header_header2_tbb(i32* %a, i32 %v, i32 %p) {
Header:
Expand Down
6 changes: 3 additions & 3 deletions llvm/test/Transforms/CallSiteSplitting/callsite-split-debug.ll
View file
Expand Up @@ -48,10 +48,10 @@ attributes #0 = { nounwind readnone speculatable }
; CallSiteBB.

; CHECK-LABEL: @foo
; CHECK-LABEL: CallsiteBB.predBB1.split:
; CHECK-LABEL: CallsiteBB.predBB.split:
; CHECK: [[TMP1:%[0-9]+]] = call i16 @bar(i16 1, i16 5)
; CHECK-LABEL: CallsiteBB.predBB2.split:
; CHECK-LABEL: CallsiteBB.predBB.split1:
; CHECK: [[TMP2:%[0-9]+]] = call i16 @bar(i16 0, i16 5)
; CHECK-LABEL: CallsiteBB
; CHECK: %phi.call = phi i16 [ [[TMP1]], %CallsiteBB.predBB1.split ], [ [[TMP2]], %CallsiteBB.predBB2.split
; CHECK: %phi.call = phi i16 [ [[TMP1]], %CallsiteBB.predBB.split ], [ [[TMP2]], %CallsiteBB.predBB.split1

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