[IR] De-virtualize ~Value to save a vptr
Summary:
Implements PR889
Removing the virtual table pointer from Value saves 1% of RSS when doing
LTO of llc on Linux. The impact on time was positive, but too noisy to
conclusively say that performance improved. Here is a link to the
spreadsheet with the original data:
https://docs.google.com/spreadsheets/d/1F4FHir0qYnV0MEp2sYYp_BuvnJgWlWPhWOwZ6LbW7W4/edit?usp=sharing
This change makes it invalid to directly delete a Value, User, or
Instruction pointer. Instead, such code can be rewritten to a null check
and a call Value::deleteValue(). Value objects tend to have their
lifetimes managed through iplist, so for the most part, this isn't a big
deal. However, there are some places where LLVM deletes values, and
those places had to be migrated to deleteValue. I have also created
llvm::unique_value, which has a custom deleter, so it can be used in
place of std::unique_ptr<Value>.
I had to add the "DerivedUser" Deleter escape hatch for MemorySSA, which
derives from User outside of lib/IR. Code in IR cannot include MemorySSA
headers or call the MemoryAccess object destructors without introducing
a circular dependency, so we need some level of indirection.
Unfortunately, no class derived from User may have any virtual methods,
because adding a virtual method would break User::getHungOffOperands(),
which assumes that it can find the use list immediately prior to the
User object. I've added a static_assert to the appropriate OperandTraits
templates to help people avoid this trap.
Reviewers: chandlerc, mehdi_amini, pete, dberlin, george.burgess.iv
Reviewed By: chandlerc
Subscribers: krytarowski, eraman, george.burgess.iv, mzolotukhin, Prazek, nlewycky, hans, inglorion, pcc, tejohnson, dberlin, llvm-commits
Differential Revision: https://reviews.llvm.org/D31261
llvm-svn: 303362
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index c04646e..0490d93 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -2057,7 +2057,7 @@
if (!performScalarPREInsertion(PREInstr, PREPred, ValNo)) {
// If we failed insertion, make sure we remove the instruction.
DEBUG(verifyRemoved(PREInstr));
- delete PREInstr;
+ PREInstr->deleteValue();
return false;
}
}
diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 54ab80e..ada22ae 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -1906,7 +1906,7 @@
{BB->getModule()->getDataLayout(), TLI, nullptr, nullptr, New})) {
ValueMapping[&*BI] = IV;
if (!New->mayHaveSideEffects()) {
- delete New;
+ New->deleteValue();
New = nullptr;
}
} else {
diff --git a/llvm/lib/Transforms/Scalar/LoopRotation.cpp b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
index 2ba9265..7312d97 100644
--- a/llvm/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
@@ -347,7 +347,7 @@
// in the map.
ValueMap[Inst] = V;
if (!C->mayHaveSideEffects()) {
- delete C;
+ C->deleteValue();
C = nullptr;
}
} else {
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index 53320bf..a20890b2 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -1582,7 +1582,7 @@
}
// No need for extra uses anymore.
- delete DummyInst;
+ DummyInst->deleteValue();
unsigned NumAddedValues = NewMulOps.size();
Value *V = EmitAddTreeOfValues(I, NewMulOps);
diff --git a/llvm/lib/Transforms/Scalar/SROA.cpp b/llvm/lib/Transforms/Scalar/SROA.cpp
index ed7df09..24bd0a2 100644
--- a/llvm/lib/Transforms/Scalar/SROA.cpp
+++ b/llvm/lib/Transforms/Scalar/SROA.cpp
@@ -2443,7 +2443,7 @@
"insert");
LI.replaceAllUsesWith(V);
Placeholder->replaceAllUsesWith(&LI);
- delete Placeholder;
+ Placeholder->deleteValue();
} else {
LI.replaceAllUsesWith(V);
}
diff --git a/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
index 2be3f5c..8b8d659 100644
--- a/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/StraightLineStrengthReduce.cpp
@@ -693,7 +693,7 @@
UnlinkedInst->setOperand(I, nullptr);
RecursivelyDeleteTriviallyDeadInstructions(Op);
}
- delete UnlinkedInst;
+ UnlinkedInst->deleteValue();
}
bool Ret = !UnlinkedInstructions.empty();
UnlinkedInstructions.clear();
diff --git a/llvm/lib/Transforms/Utils/CloneFunction.cpp b/llvm/lib/Transforms/Utils/CloneFunction.cpp
index 4aa26fd..bf2ab7c 100644
--- a/llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ b/llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -317,7 +317,7 @@
if (!NewInst->mayHaveSideEffects()) {
VMap[&*II] = V;
- delete NewInst;
+ NewInst->deleteValue();
continue;
}
}
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index b44bc74..5a04cac 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2235,7 +2235,7 @@
if (!BBI->use_empty())
TranslateMap[&*BBI] = V;
if (!N->mayHaveSideEffects()) {
- delete N; // Instruction folded away, don't need actual inst
+ N->deleteValue(); // Instruction folded away, don't need actual inst
N = nullptr;
}
} else {
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 64013d6..e6f78e6 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -578,12 +578,12 @@
void eraseInstruction(Instruction *I) {
I->removeFromParent();
I->dropAllReferences();
- DeletedInstructions.push_back(std::unique_ptr<Instruction>(I));
+ DeletedInstructions.emplace_back(I);
}
/// Temporary store for deleted instructions. Instructions will be deleted
/// eventually when the BoUpSLP is destructed.
- SmallVector<std::unique_ptr<Instruction>, 8> DeletedInstructions;
+ SmallVector<unique_value, 8> DeletedInstructions;
/// A list of values that need to extracted out of the tree.
/// This list holds pairs of (Internal Scalar : External User). External User