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[Attributor][NFC] Ignore benign uses in AAMemoryBehaviorFloating 

In AAMemoryBehaviorFloating we used to track benign uses in a SetVector.
With this change we look through benign uses eagerly to reduce the
number of elements (=Uses) we look at during an update.

The test does actually not fail prior to this commit but I already wrote
it so I kept it.
This commit is contained in:
Johannes Doerfert 2020-09-07 17:55:05 -05:00
parent 66e4f07198
commit 957094e31b
2 changed files with 78 additions and 9 deletions
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41
llvm/lib/Transforms/IPO/AttributorAttributes.cpp
View File

@ -5861,9 +5861,7 @@ struct AAMemoryBehaviorFloating : AAMemoryBehaviorImpl {
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AAMemoryBehaviorImpl::initialize(A);
// Initialize the use vector with all direct uses of the associated value.
for (const Use &U : getAssociatedValue().uses())
Uses.insert(&U);
addUsesOf(A, getAssociatedValue());
}
/// See AbstractAttribute::updateImpl(...).
@ -5889,8 +5887,14 @@ private:
void analyzeUseIn(Attributor &A, const Use *U, const Instruction *UserI);
protected:
/// Add the uses of \p V to the `Uses` set we look at during the update step.
void addUsesOf(Attributor &A, const Value &V);
/// Container for (transitive) uses of the associated argument.
SetVector<const Use *> Uses;
SmallVector<const Use *, 8> Uses;
/// Set to remember the uses we already traversed.
SmallPtrSet<const Use *, 8> Visited;
};
/// Memory behavior attribute for function argument.
@ -5915,9 +5919,7 @@ struct AAMemoryBehaviorArgument : AAMemoryBehaviorFloating {
if (!Arg || !A.isFunctionIPOAmendable(*(Arg->getParent()))) {
indicatePessimisticFixpoint();
} else {
// Initialize the use vector with all direct uses of the associated value.
for (const Use &U : Arg->uses())
Uses.insert(&U);
addUsesOf(A, *Arg);
}
}
@ -6169,8 +6171,7 @@ ChangeStatus AAMemoryBehaviorFloating::updateImpl(Attributor &A) {
// Check if the users of UserI should also be visited.
if (followUsersOfUseIn(A, U, UserI))
for (const Use &UserIUse : UserI->uses())
Uses.insert(&UserIUse);
addUsesOf(A, *UserI);
// If UserI might touch memory we analyze the use in detail.
if (UserI->mayReadOrWriteMemory())
@ -6181,6 +6182,28 @@ ChangeStatus AAMemoryBehaviorFloating::updateImpl(Attributor &A) {
: ChangeStatus::UNCHANGED;
}
void AAMemoryBehaviorFloating::addUsesOf(Attributor &A, const Value &V) {
SmallVector<const Use *, 8> WL;
for (const Use &U : V.uses())
WL.push_back(&U);
while (!WL.empty()) {
const Use *U = WL.pop_back_val();
if (!Visited.insert(U).second)
continue;
const Instruction *UserI = cast<Instruction>(U->getUser());
if (UserI->mayReadOrWriteMemory()) {
Uses.push_back(U);
continue;
}
if (!followUsersOfUseIn(A, U, UserI))
continue;
for (const Use &UU : UserI->uses())
WL.push_back(&UU);
}
}
bool AAMemoryBehaviorFloating::followUsersOfUseIn(Attributor &A, const Use *U,
const Instruction *UserI) {
// The loaded value is unrelated to the pointer argument, no need to

46
llvm/test/Transforms/Attributor/readattrs.ll
View File

@ -403,3 +403,49 @@ define void @ptr_uses(i8* %ptr) {
call void @val_use(i8 %call_val)
ret void
}
define void @ptr_use_chain(i8* %ptr) {
; CHECK-LABEL: define {{[^@]+}}@ptr_use_chain
; CHECK-SAME: (i8* [[PTR:%.*]])
; CHECK-NEXT: [[BC0:%.*]] = bitcast i8* [[PTR]] to i32*
; CHECK-NEXT: [[BC1:%.*]] = bitcast i32* [[BC0]] to i8*
; CHECK-NEXT: [[BC2:%.*]] = bitcast i8* [[BC1]] to i32*
; CHECK-NEXT: [[BC3:%.*]] = bitcast i32* [[BC2]] to i8*
; CHECK-NEXT: [[BC4:%.*]] = bitcast i8* [[BC3]] to i32*
; CHECK-NEXT: [[BC5:%.*]] = bitcast i32* [[BC4]] to i8*
; CHECK-NEXT: [[BC6:%.*]] = bitcast i8* [[BC5]] to i32*
; CHECK-NEXT: [[BC7:%.*]] = bitcast i32* [[BC6]] to i8*
; CHECK-NEXT: [[BC8:%.*]] = bitcast i8* [[BC7]] to i32*
; CHECK-NEXT: [[BC9:%.*]] = bitcast i32* [[BC8]] to i8*
; CHECK-NEXT: [[ABC2:%.*]] = bitcast i8* [[BC9]] to i32*
; CHECK-NEXT: [[ABC3:%.*]] = bitcast i32* [[ABC2]] to i8*
; CHECK-NEXT: [[ABC4:%.*]] = bitcast i8* [[ABC3]] to i32*
; CHECK-NEXT: [[ABC5:%.*]] = bitcast i32* [[ABC4]] to i8*
; CHECK-NEXT: [[ABC6:%.*]] = bitcast i8* [[ABC5]] to i32*
; CHECK-NEXT: [[ABC7:%.*]] = bitcast i32* [[ABC6]] to i8*
; CHECK-NEXT: [[ABC8:%.*]] = bitcast i8* [[ABC7]] to i32*
; CHECK-NEXT: [[ABC9:%.*]] = bitcast i32* [[ABC8]] to i8*
; CHECK-NEXT: call void @escape_i8(i8* [[ABC9]])
; CHECK-NEXT: ret void
;
%bc0 = bitcast i8* %ptr to i32*
%bc1 = bitcast i32* %bc0 to i8*
%bc2 = bitcast i8* %bc1 to i32*
%bc3 = bitcast i32* %bc2 to i8*
%bc4 = bitcast i8* %bc3 to i32*
%bc5 = bitcast i32* %bc4 to i8*
%bc6 = bitcast i8* %bc5 to i32*
%bc7 = bitcast i32* %bc6 to i8*
%bc8 = bitcast i8* %bc7 to i32*
%bc9 = bitcast i32* %bc8 to i8*
%abc2 = bitcast i8* %bc9 to i32*
%abc3 = bitcast i32* %abc2 to i8*
%abc4 = bitcast i8* %abc3 to i32*
%abc5 = bitcast i32* %abc4 to i8*
%abc6 = bitcast i8* %abc5 to i32*
%abc7 = bitcast i32* %abc6 to i8*
%abc8 = bitcast i8* %abc7 to i32*
%abc9 = bitcast i32* %abc8 to i8*
call void @escape_i8(i8* %abc9)
ret void
}