[llvm-branch-commits] [llvm] bc849e5 - Revert "[FuncSpec] Add Phi nodes to the InstCostVisitor."
Alexandros Lamprineas via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Wed Jul 26 11:53:21 PDT 2023
Author: Alexandros Lamprineas
Date: 2023-07-26T19:10:55+01:00
New Revision: bc849e525f80208d8449480d66f8f432441810db
URL: https://github.com/llvm/llvm-project/commit/bc849e525f80208d8449480d66f8f432441810db
DIFF: https://github.com/llvm/llvm-project/commit/bc849e525f80208d8449480d66f8f432441810db.diff
LOG: Revert "[FuncSpec] Add Phi nodes to the InstCostVisitor."
This reverts commit 03f1d09fe484f6c924434bc9c888e022b3514455
because of a crash reported on https://reviews.llvm.org/D154852
Added:
Modified:
llvm/include/llvm/Transforms/IPO/FunctionSpecialization.h
llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
llvm/unittests/Transforms/IPO/FunctionSpecializationTest.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Transforms/IPO/FunctionSpecialization.h b/llvm/include/llvm/Transforms/IPO/FunctionSpecialization.h
index 4e78d9db024c56..f780385f7f67da 100644
--- a/llvm/include/llvm/Transforms/IPO/FunctionSpecialization.h
+++ b/llvm/include/llvm/Transforms/IPO/FunctionSpecialization.h
@@ -126,15 +126,6 @@ class InstCostVisitor : public InstVisitor<InstCostVisitor, Constant *> {
SCCPSolver &Solver;
ConstMap KnownConstants;
- // Basic blocks known to be unreachable after constant propagation.
- DenseSet<BasicBlock *> DeadBlocks;
- // PHI nodes we have visited before.
- DenseSet<Instruction *> VisitedPHIs;
- // PHI nodes we have visited once without successfully constant folding them.
- // Once the InstCostVisitor has processed all the specialization arguments,
- // it should be possible to determine whether those PHIs can be folded
- // (some of their incoming values may have become constant or dead).
- SmallVector<Instruction *> PendingPHIs;
ConstMap::iterator LastVisited;
@@ -143,10 +134,7 @@ class InstCostVisitor : public InstVisitor<InstCostVisitor, Constant *> {
TargetTransformInfo &TTI, SCCPSolver &Solver)
: DL(DL), BFI(BFI), TTI(TTI), Solver(Solver) {}
- Cost getUserBonus(Instruction *User, Value *Use = nullptr,
- Constant *C = nullptr);
-
- Cost getBonusFromPendingPHIs();
+ Cost getUserBonus(Instruction *User, Value *Use, Constant *C);
private:
friend class InstVisitor<InstCostVisitor, Constant *>;
@@ -155,7 +143,6 @@ class InstCostVisitor : public InstVisitor<InstCostVisitor, Constant *> {
Cost estimateBranchInst(BranchInst &I);
Constant *visitInstruction(Instruction &I) { return nullptr; }
- Constant *visitPHINode(PHINode &I);
Constant *visitFreezeInst(FreezeInst &I);
Constant *visitCallBase(CallBase &I);
Constant *visitLoadInst(LoadInst &I);
diff --git a/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp b/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
index 3d6c501e45968e..ac5dbc7cfb2a56 100644
--- a/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
@@ -78,11 +78,6 @@ static cl::opt<unsigned> MaxClones(
"The maximum number of clones allowed for a single function "
"specialization"));
-static cl::opt<unsigned> MaxIncomingPhiValues(
- "funcspec-max-incoming-phi-values", cl::init(4), cl::Hidden, cl::desc(
- "The maximum number of incoming values a PHI node can have to be "
- "considered during the specialization bonus estimation"));
-
static cl::opt<unsigned> MinFunctionSize(
"funcspec-min-function-size", cl::init(100), cl::Hidden, cl::desc(
"Don't specialize functions that have less than this number of "
@@ -109,7 +104,6 @@ static cl::opt<bool> SpecializeLiteralConstant(
// the combination of size and latency savings in comparison to the non
// specialized version of the function.
static Cost estimateBasicBlocks(SmallVectorImpl<BasicBlock *> &WorkList,
- DenseSet<BasicBlock *> &DeadBlocks,
ConstMap &KnownConstants, SCCPSolver &Solver,
BlockFrequencyInfo &BFI,
TargetTransformInfo &TTI) {
@@ -124,12 +118,6 @@ static Cost estimateBasicBlocks(SmallVectorImpl<BasicBlock *> &WorkList,
if (!Weight)
continue;
- // These blocks are considered dead as far as the InstCostVisitor is
- // concerned. They haven't been proven dead yet by the Solver, but
- // may become if we propagate the constant specialization arguments.
- if (!DeadBlocks.insert(BB).second)
- continue;
-
for (Instruction &I : *BB) {
// Disregard SSA copies.
if (auto *II = dyn_cast<IntrinsicInst>(&I))
@@ -164,19 +152,9 @@ static Constant *findConstantFor(Value *V, ConstMap &KnownConstants) {
return nullptr;
}
-Cost InstCostVisitor::getBonusFromPendingPHIs() {
- Cost Bonus = 0;
- while (!PendingPHIs.empty()) {
- Instruction *Phi = PendingPHIs.pop_back_val();
- Bonus += getUserBonus(Phi);
- }
- return Bonus;
-}
-
Cost InstCostVisitor::getUserBonus(Instruction *User, Value *Use, Constant *C) {
// Cache the iterator before visiting.
- LastVisited = Use ? KnownConstants.insert({Use, C}).first
- : KnownConstants.end();
+ LastVisited = KnownConstants.insert({Use, C}).first;
if (auto *I = dyn_cast<SwitchInst>(User))
return estimateSwitchInst(*I);
@@ -203,15 +181,13 @@ Cost InstCostVisitor::getUserBonus(Instruction *User, Value *Use, Constant *C) {
for (auto *U : User->users())
if (auto *UI = dyn_cast<Instruction>(U))
- if (UI != User && Solver.isBlockExecutable(UI->getParent()))
+ if (Solver.isBlockExecutable(UI->getParent()))
Bonus += getUserBonus(UI, User, C);
return Bonus;
}
Cost InstCostVisitor::estimateSwitchInst(SwitchInst &I) {
- assert(LastVisited != KnownConstants.end() && "Invalid iterator!");
-
if (I.getCondition() != LastVisited->first)
return 0;
@@ -232,13 +208,10 @@ Cost InstCostVisitor::estimateSwitchInst(SwitchInst &I) {
WorkList.push_back(BB);
}
- return estimateBasicBlocks(WorkList, DeadBlocks, KnownConstants, Solver, BFI,
- TTI);
+ return estimateBasicBlocks(WorkList, KnownConstants, Solver, BFI, TTI);
}
Cost InstCostVisitor::estimateBranchInst(BranchInst &I) {
- assert(LastVisited != KnownConstants.end() && "Invalid iterator!");
-
if (I.getCondition() != LastVisited->first)
return 0;
@@ -250,39 +223,10 @@ Cost InstCostVisitor::estimateBranchInst(BranchInst &I) {
Succ->getUniquePredecessor() == I.getParent())
WorkList.push_back(Succ);
- return estimateBasicBlocks(WorkList, DeadBlocks, KnownConstants, Solver, BFI,
- TTI);
-}
-
-Constant *InstCostVisitor::visitPHINode(PHINode &I) {
- if (I.getNumIncomingValues() > MaxIncomingPhiValues)
- return nullptr;
-
- bool Inserted = VisitedPHIs.insert(&I).second;
- Constant *Const = nullptr;
-
- for (unsigned Idx = 0, E = I.getNumIncomingValues(); Idx != E; ++Idx) {
- Value *V = I.getIncomingValue(Idx);
- if (auto *Inst = dyn_cast<Instruction>(V))
- if (Inst == &I || DeadBlocks.contains(I.getIncomingBlock(Idx)))
- continue;
- Constant *C = findConstantFor(V, KnownConstants);
- if (!C) {
- if (Inserted)
- PendingPHIs.push_back(&I);
- return nullptr;
- }
- if (!Const)
- Const = C;
- else if (C != Const)
- return nullptr;
- }
- return Const;
+ return estimateBasicBlocks(WorkList, KnownConstants, Solver, BFI, TTI);
}
Constant *InstCostVisitor::visitFreezeInst(FreezeInst &I) {
- assert(LastVisited != KnownConstants.end() && "Invalid iterator!");
-
if (isGuaranteedNotToBeUndefOrPoison(LastVisited->second))
return LastVisited->second;
return nullptr;
@@ -309,8 +253,6 @@ Constant *InstCostVisitor::visitCallBase(CallBase &I) {
}
Constant *InstCostVisitor::visitLoadInst(LoadInst &I) {
- assert(LastVisited != KnownConstants.end() && "Invalid iterator!");
-
if (isa<ConstantPointerNull>(LastVisited->second))
return nullptr;
return ConstantFoldLoadFromConstPtr(LastVisited->second, I.getType(), DL);
@@ -333,8 +275,6 @@ Constant *InstCostVisitor::visitGetElementPtrInst(GetElementPtrInst &I) {
}
Constant *InstCostVisitor::visitSelectInst(SelectInst &I) {
- assert(LastVisited != KnownConstants.end() && "Invalid iterator!");
-
if (I.getCondition() != LastVisited->first)
return nullptr;
@@ -350,8 +290,6 @@ Constant *InstCostVisitor::visitCastInst(CastInst &I) {
}
Constant *InstCostVisitor::visitCmpInst(CmpInst &I) {
- assert(LastVisited != KnownConstants.end() && "Invalid iterator!");
-
bool Swap = I.getOperand(1) == LastVisited->first;
Value *V = Swap ? I.getOperand(0) : I.getOperand(1);
Constant *Other = findConstantFor(V, KnownConstants);
@@ -365,14 +303,10 @@ Constant *InstCostVisitor::visitCmpInst(CmpInst &I) {
}
Constant *InstCostVisitor::visitUnaryOperator(UnaryOperator &I) {
- assert(LastVisited != KnownConstants.end() && "Invalid iterator!");
-
return ConstantFoldUnaryOpOperand(I.getOpcode(), LastVisited->second, DL);
}
Constant *InstCostVisitor::visitBinaryOperator(BinaryOperator &I) {
- assert(LastVisited != KnownConstants.end() && "Invalid iterator!");
-
bool Swap = I.getOperand(1) == LastVisited->first;
Value *V = Swap ? I.getOperand(0) : I.getOperand(1);
Constant *Other = findConstantFor(V, KnownConstants);
@@ -779,17 +713,13 @@ bool FunctionSpecializer::findSpecializations(Function *F, Cost SpecCost,
AllSpecs[Index].CallSites.push_back(&CS);
} else {
// Calculate the specialisation gain.
- Cost Score = 0;
+ Cost Score = 0 - SpecCost;
InstCostVisitor Visitor = getInstCostVisitorFor(F);
for (ArgInfo &A : S.Args)
Score += getSpecializationBonus(A.Formal, A.Actual, Visitor);
- Score += Visitor.getBonusFromPendingPHIs();
-
- LLVM_DEBUG(dbgs() << "FnSpecialization: Specialization score = "
- << Score << "\n");
// Discard unprofitable specialisations.
- if (!ForceSpecialization && Score <= SpecCost)
+ if (!ForceSpecialization && Score <= 0)
continue;
// Create a new specialisation entry.
diff --git a/llvm/unittests/Transforms/IPO/FunctionSpecializationTest.cpp b/llvm/unittests/Transforms/IPO/FunctionSpecializationTest.cpp
index be6f8fc990b3c7..222311dc040a86 100644
--- a/llvm/unittests/Transforms/IPO/FunctionSpecializationTest.cpp
+++ b/llvm/unittests/Transforms/IPO/FunctionSpecializationTest.cpp
@@ -287,56 +287,3 @@ TEST_F(FunctionSpecializationTest, Misc) {
Bonus = Specializer.getSpecializationBonus(F->getArg(3), Undef, Visitor);
EXPECT_TRUE(Bonus == 0);
}
-
-TEST_F(FunctionSpecializationTest, PhiNode) {
- const char *ModuleString = R"(
- define void @foo(i32 %a, i32 %b, i32 %i) {
- entry:
- br label %loop
- loop:
- switch i32 %i, label %default
- [ i32 1, label %case1
- i32 2, label %case2 ]
- case1:
- %0 = add i32 %a, 1
- br label %bb
- case2:
- %1 = sub i32 %b, 1
- br label %bb
- bb:
- %2 = phi i32 [ %0, %case1 ], [ %1, %case2 ], [ %2, %bb ]
- %3 = icmp eq i32 %2, 2
- br i1 %3, label %bb, label %loop
- default:
- ret void
- }
- )";
-
- Module &M = parseModule(ModuleString);
- Function *F = M.getFunction("foo");
- FunctionSpecializer Specializer = getSpecializerFor(F);
- InstCostVisitor Visitor = Specializer.getInstCostVisitorFor(F);
-
- Constant *One = ConstantInt::get(IntegerType::getInt32Ty(M.getContext()), 1);
-
- auto FuncIter = F->begin();
- for (int I = 0; I < 4; ++I)
- ++FuncIter;
-
- BasicBlock &BB = *FuncIter;
-
- Instruction &Phi = BB.front();
- Instruction &Icmp = *++BB.begin();
-
- Cost Bonus = Specializer.getSpecializationBonus(F->getArg(0), One, Visitor) +
- Specializer.getSpecializationBonus(F->getArg(1), One, Visitor) +
- Specializer.getSpecializationBonus(F->getArg(2), One, Visitor);
- EXPECT_TRUE(Bonus > 0);
-
- // phi + icmp
- Cost Ref = getInstCost(Phi) + getInstCost(Icmp);
- Bonus = Visitor.getBonusFromPendingPHIs();
- EXPECT_EQ(Bonus, Ref);
- EXPECT_TRUE(Bonus > 0);
-}
-
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