[Reland][InstCombine] Iterative replacement in PtrReplacer #144626
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This patch enhances the PtrReplacer as follows: 1. Users are now collected iteratively to be generous on the stack. In the case of PHIs with incoming values which have not yet been visited, they are pushed back into the stack for reconsideration. 2. Replace users of the pointer root in a reverse-postorder traversal, instead of a simple traversal over the collected users. This reordering ensures that the uses of an instruction are replaced before replacing the instruction itself. 3. During the replacement of PHI, use the same incoming value if it does not have a replacement. This patch specifically fixes the case when an incoming value of a PHI is addrspacecasted.
llvmbot
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backend:AMDGPU
llvm:instcombine
|
@llvm/pr-subscribers-llvm-transforms @llvm/pr-subscribers-backend-amdgpu Author: Anshil Gandhi (gandhi56) ChangesThis patch enhances the PtrReplacer as follows:
This patch specifically fixes the case when an incoming value of a PHI is addrspacecasted. This is a reland of #137215. Full diff: https://github.com/llvm/llvm-project/pull/144626.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index c29cba6f675c5..8267cad94938c 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -244,11 +244,10 @@ class PointerReplacer {
void replacePointer(Value *V);
private:
- bool collectUsersRecursive(Instruction &I);
void replace(Instruction *I);
- Value *getReplacement(Value *I);
+ Value *getReplacement(Value *V) const { return WorkMap.lookup(V); }
bool isAvailable(Instruction *I) const {
- return I == &Root || Worklist.contains(I);
+ return I == &Root || UsersToReplace.contains(I);
}
bool isEqualOrValidAddrSpaceCast(const Instruction *I,
@@ -260,8 +259,7 @@ class PointerReplacer {
return (FromAS == ToAS) || IC.isValidAddrSpaceCast(FromAS, ToAS);
}
- SmallPtrSet<Instruction *, 32> ValuesToRevisit;
- SmallSetVector<Instruction *, 4> Worklist;
+ SmallSetVector<Instruction *, 32> UsersToReplace;
MapVector<Value *, Value *> WorkMap;
InstCombinerImpl &IC;
Instruction &Root;
@@ -270,72 +268,79 @@ class PointerReplacer {
} // end anonymous namespace
bool PointerReplacer::collectUsers() {
- if (!collectUsersRecursive(Root))
- return false;
-
- // Ensure that all outstanding (indirect) users of I
- // are inserted into the Worklist. Return false
- // otherwise.
- return llvm::set_is_subset(ValuesToRevisit, Worklist);
-}
+ SmallVector<Instruction *> Worklist;
+ SmallSetVector<Instruction *, 32> ValuesToRevisit;
+
+ auto PushUsersToWorklist = [&](Instruction *Inst) {
+ for (auto *U : Inst->users())
+ if (auto *I = dyn_cast<Instruction>(U))
+ if (!isAvailable(I) && !ValuesToRevisit.contains(I))
+ Worklist.emplace_back(I);
+ };
-bool PointerReplacer::collectUsersRecursive(Instruction &I) {
- for (auto *U : I.users()) {
- auto *Inst = cast<Instruction>(&*U);
+ PushUsersToWorklist(&Root);
+ while (!Worklist.empty()) {
+ Instruction *Inst = Worklist.pop_back_val();
if (auto *Load = dyn_cast<LoadInst>(Inst)) {
if (Load->isVolatile())
return false;
- Worklist.insert(Load);
+ UsersToReplace.insert(Load);
} else if (auto *PHI = dyn_cast<PHINode>(Inst)) {
- // All incoming values must be instructions for replacability
- if (any_of(PHI->incoming_values(),
- [](Value *V) { return !isa<Instruction>(V); }))
- return false;
-
- // If at least one incoming value of the PHI is not in Worklist,
- // store the PHI for revisiting and skip this iteration of the
- // loop.
- if (any_of(PHI->incoming_values(), [this](Value *V) {
- return !isAvailable(cast<Instruction>(V));
+ /// TODO: Handle poison and null pointers for PHI and select.
+ // If all incoming values are available, mark this PHI as
+ // replacable and push it's users into the worklist.
+ bool IsReplacable = true;
+ if (all_of(PHI->incoming_values(), [&](Value *V) {
+ if (!isa<Instruction>(V))
+ return IsReplacable = false;
+ return isAvailable(cast<Instruction>(V));
})) {
- ValuesToRevisit.insert(Inst);
+ UsersToReplace.insert(PHI);
+ PushUsersToWorklist(PHI);
continue;
}
- Worklist.insert(PHI);
- if (!collectUsersRecursive(*PHI))
- return false;
- } else if (auto *SI = dyn_cast<SelectInst>(Inst)) {
- if (!isa<Instruction>(SI->getTrueValue()) ||
- !isa<Instruction>(SI->getFalseValue()))
+ // Either an incoming value is not an instruction or not all
+ // incoming values are available. If this PHI was already
+ // visited prior to this iteration, return false.
+ if (!IsReplacable || !ValuesToRevisit.insert(PHI))
return false;
- if (!isAvailable(cast<Instruction>(SI->getTrueValue())) ||
- !isAvailable(cast<Instruction>(SI->getFalseValue()))) {
- ValuesToRevisit.insert(Inst);
- continue;
+ // Push PHI back into the stack, followed by unavailable
+ // incoming values.
+ Worklist.emplace_back(PHI);
+ for (unsigned Idx = 0; Idx < PHI->getNumIncomingValues(); ++Idx) {
+ auto *IncomingValue = cast<Instruction>(PHI->getIncomingValue(Idx));
+ if (UsersToReplace.contains(IncomingValue))
+ continue;
+ if (!ValuesToRevisit.insert(IncomingValue))
+ return false;
+ Worklist.emplace_back(IncomingValue);
}
- Worklist.insert(SI);
- if (!collectUsersRecursive(*SI))
- return false;
- } else if (isa<GetElementPtrInst>(Inst)) {
- Worklist.insert(Inst);
- if (!collectUsersRecursive(*Inst))
+ } else if (auto *SI = dyn_cast<SelectInst>(Inst)) {
+ auto *TrueInst = dyn_cast<Instruction>(SI->getTrueValue());
+ auto *FalseInst = dyn_cast<Instruction>(SI->getFalseValue());
+ if (!TrueInst || !FalseInst)
return false;
+
+ UsersToReplace.insert(SI);
+ PushUsersToWorklist(SI);
+ } else if (auto *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
+ UsersToReplace.insert(GEP);
+ PushUsersToWorklist(GEP);
} else if (auto *MI = dyn_cast<MemTransferInst>(Inst)) {
if (MI->isVolatile())
return false;
- Worklist.insert(Inst);
+ UsersToReplace.insert(Inst);
} else if (isEqualOrValidAddrSpaceCast(Inst, FromAS)) {
- Worklist.insert(Inst);
- if (!collectUsersRecursive(*Inst))
- return false;
+ UsersToReplace.insert(Inst);
+ PushUsersToWorklist(Inst);
} else if (Inst->isLifetimeStartOrEnd()) {
continue;
} else {
// TODO: For arbitrary uses with address space mismatches, should we check
// if we can introduce a valid addrspacecast?
- LLVM_DEBUG(dbgs() << "Cannot handle pointer user: " << *U << '\n');
+ LLVM_DEBUG(dbgs() << "Cannot handle pointer user: " << *Inst << '\n');
return false;
}
}
@@ -343,7 +348,39 @@ bool PointerReplacer::collectUsersRecursive(Instruction &I) {
return true;
}
-Value *PointerReplacer::getReplacement(Value *V) { return WorkMap.lookup(V); }
+void PointerReplacer::replacePointer(Value *V) {
+ assert(cast<PointerType>(Root.getType()) != cast<PointerType>(V->getType()) &&
+ "Invalid usage");
+ WorkMap[&Root] = V;
+ SmallVector<Instruction *> Worklist;
+ SetVector<Instruction *> PostOrderWorklist;
+ SmallPtrSet<Instruction *, 32> Visited;
+
+ // Perform a postorder traversal of the users of Root.
+ Worklist.push_back(&Root);
+ while (!Worklist.empty()) {
+ Instruction *I = Worklist.back();
+
+ // If I has not been processed before, push each of its
+ // replacable users into the worklist.
+ if (Visited.insert(I).second) {
+ for (auto *U : I->users()) {
+ auto *UserInst = cast<Instruction>(U);
+ if (UsersToReplace.contains(UserInst))
+ Worklist.push_back(UserInst);
+ }
+ // Otherwise, users of I have already been pushed into
+ // the PostOrderWorklist. Push I as well.
+ } else {
+ PostOrderWorklist.insert(I);
+ Worklist.pop_back();
+ }
+ }
+
+ // Replace pointers in reverse-postorder.
+ for (Instruction *I : reverse(PostOrderWorklist))
+ replace(I);
+}
void PointerReplacer::replace(Instruction *I) {
if (getReplacement(I))
@@ -365,13 +402,15 @@ void PointerReplacer::replace(Instruction *I) {
// replacement (new value).
WorkMap[NewI] = NewI;
} else if (auto *PHI = dyn_cast<PHINode>(I)) {
- Type *NewTy = getReplacement(PHI->getIncomingValue(0))->getType();
- auto *NewPHI = PHINode::Create(NewTy, PHI->getNumIncomingValues(),
- PHI->getName(), PHI->getIterator());
- for (unsigned int I = 0; I < PHI->getNumIncomingValues(); ++I)
- NewPHI->addIncoming(getReplacement(PHI->getIncomingValue(I)),
- PHI->getIncomingBlock(I));
- WorkMap[PHI] = NewPHI;
+ // Create a new PHI by replacing any incoming value that is a user of the
+ // root pointer and has a replacement.
+ Value *V = WorkMap.lookup(PHI->getIncomingValue(0));
+ PHI->mutateType(V ? V->getType() : PHI->getIncomingValue(0)->getType());
+ for (unsigned int I = 0; I < PHI->getNumIncomingValues(); ++I) {
+ Value *V = WorkMap.lookup(PHI->getIncomingValue(I));
+ PHI->setIncomingValue(I, V ? V : PHI->getIncomingValue(I));
+ }
+ WorkMap[PHI] = PHI;
} else if (auto *GEP = dyn_cast<GetElementPtrInst>(I)) {
auto *V = getReplacement(GEP->getPointerOperand());
assert(V && "Operand not replaced");
@@ -435,18 +474,6 @@ void PointerReplacer::replace(Instruction *I) {
}
}
-void PointerReplacer::replacePointer(Value *V) {
-#ifndef NDEBUG
- auto *PT = cast<PointerType>(Root.getType());
- auto *NT = cast<PointerType>(V->getType());
- assert(PT != NT && "Invalid usage");
-#endif
- WorkMap[&Root] = V;
-
- for (Instruction *Workitem : Worklist)
- replace(Workitem);
-}
-
Instruction *InstCombinerImpl::visitAllocaInst(AllocaInst &AI) {
if (auto *I = simplifyAllocaArraySize(*this, AI, DT))
return I;
diff --git a/llvm/test/Transforms/InstCombine/AMDGPU/ptr-replace-alloca.ll b/llvm/test/Transforms/InstCombine/AMDGPU/ptr-replace-alloca.ll
new file mode 100644
index 0000000000000..538cc19f9722e
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/AMDGPU/ptr-replace-alloca.ll
@@ -0,0 +1,79 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -mtriple=amdgcn-amd-amdhsa -passes=instcombine -S < %s | FileCheck %s
+
+%struct.type = type { [256 x <2 x i64>] }
+@g1 = external hidden addrspace(3) global %struct.type, align 16
+
+; This test requires the PtrReplacer to replace users in an RPO traversal.
+; Furthermore, %ptr.else need not to be replaced so it must be retained in
+; %ptr.sink.
+define <2 x i64> @func(ptr addrspace(4) byref(%struct.type) align 16 %0, i1 %cmp.0) {
+; CHECK-LABEL: define <2 x i64> @func(
+; CHECK-SAME: ptr addrspace(4) byref([[STRUCT_TYPE:%.*]]) align 16 [[TMP0:%.*]], i1 [[CMP_0:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: br i1 [[CMP_0]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
+; CHECK: [[IF_THEN]]:
+; CHECK-NEXT: [[VAL_THEN:%.*]] = addrspacecast ptr addrspace(4) [[TMP0]] to ptr
+; CHECK-NEXT: br label %[[SINK:.*]]
+; CHECK: [[IF_ELSE]]:
+; CHECK-NEXT: [[PTR_ELSE:%.*]] = load ptr, ptr addrspace(3) getelementptr inbounds nuw (i8, ptr addrspace(3) @g1, i32 32), align 16
+; CHECK-NEXT: br label %[[SINK]]
+; CHECK: [[SINK]]:
+; CHECK-NEXT: [[PTR_SINK:%.*]] = phi ptr [ [[PTR_ELSE]], %[[IF_ELSE]] ], [ [[VAL_THEN]], %[[IF_THEN]] ]
+; CHECK-NEXT: [[VAL_SINK:%.*]] = load <2 x i64>, ptr [[PTR_SINK]], align 16
+; CHECK-NEXT: ret <2 x i64> [[VAL_SINK]]
+;
+entry:
+ %coerce = alloca %struct.type, align 16, addrspace(5)
+ call void @llvm.memcpy.p5.p4.i64(ptr addrspace(5) align 16 %coerce, ptr addrspace(4) align 16 %0, i64 4096, i1 false)
+ br i1 %cmp.0, label %if.then, label %if.else
+
+if.then: ; preds = %entry
+ %ptr.then = getelementptr inbounds i8, ptr addrspace(5) %coerce, i64 0
+ %val.then = addrspacecast ptr addrspace(5) %ptr.then to ptr
+ br label %sink
+
+if.else: ; preds = %entry
+ %ptr.else = load ptr, ptr addrspace(3) getelementptr inbounds nuw (i8, ptr addrspace(3) @g1, i32 32), align 16
+ %val.else = getelementptr inbounds nuw i8, ptr %ptr.else, i64 0
+ br label %sink
+
+sink:
+ %ptr.sink = phi ptr [ %val.else, %if.else ], [ %val.then, %if.then ]
+ %val.sink = load <2 x i64>, ptr %ptr.sink, align 16
+ ret <2 x i64> %val.sink
+}
+
+define <2 x i64> @func_phi_loop(ptr addrspace(4) byref(%struct.type) align 16 %0, i1 %cmp.0) {
+; CHECK-LABEL: define <2 x i64> @func_phi_loop(
+; CHECK-SAME: ptr addrspace(4) byref([[STRUCT_TYPE:%.*]]) align 16 [[TMP0:%.*]], i1 [[CMP_0:%.*]]) {
+; CHECK-NEXT: [[ENTRY:.*]]:
+; CHECK-NEXT: [[VAL_0:%.*]] = addrspacecast ptr addrspace(4) [[TMP0]] to ptr
+; CHECK-NEXT: br label %[[LOOP:.*]]
+; CHECK: [[LOOP]]:
+; CHECK-NEXT: [[PTR_PHI_R:%.*]] = phi ptr [ [[PTR_1:%.*]], %[[LOOP]] ], [ [[VAL_0]], %[[ENTRY]] ]
+; CHECK-NEXT: [[PTR_1]] = load ptr, ptr addrspace(3) getelementptr inbounds nuw (i8, ptr addrspace(3) @g1, i32 32), align 16
+; CHECK-NEXT: br i1 [[CMP_0]], label %[[LOOP]], label %[[SINK:.*]]
+; CHECK: [[SINK]]:
+; CHECK-NEXT: [[VAL_SINK:%.*]] = load <2 x i64>, ptr [[PTR_PHI_R]], align 16
+; CHECK-NEXT: ret <2 x i64> [[VAL_SINK]]
+;
+entry:
+ %coerce = alloca %struct.type, align 16, addrspace(5)
+ call void @llvm.memcpy.p5.p4.i64(ptr addrspace(5) align 16 %coerce, ptr addrspace(4) align 16 %0, i64 4096, i1 false)
+ %ptr.0 = getelementptr inbounds i8, ptr addrspace(5) %coerce, i64 0
+ %val.0 = addrspacecast ptr addrspace(5) %ptr.0 to ptr
+ br label %loop
+
+loop:
+ %ptr.phi = phi ptr [ %val.1, %loop ], [ %val.0, %entry ]
+ %ptr.1 = load ptr, ptr addrspace(3) getelementptr inbounds nuw (i8, ptr addrspace(3) @g1, i32 32), align 16
+ %val.1 = getelementptr inbounds nuw i8, ptr %ptr.1, i64 0
+ br i1 %cmp.0, label %loop, label %sink
+
+sink:
+ %val.sink = load <2 x i64>, ptr %ptr.phi, align 16
+ ret <2 x i64> %val.sink
+}
+
+declare void @llvm.memcpy.p5.p4.i64(ptr addrspace(5) noalias writeonly captures(none), ptr addrspace(4) noalias readonly captures(none), i64, i1 immarg) #0
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If it is a reland, you probably want to make the title more specific. The description might be about what extra stuff is done on top of the reverted commit. |
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Yup, I am not sure exactly which tests failed previously in the LLVM CI. I re-triggered GitHub CI and internal PSDB. At the moment, there are no changes in this PR. |
gandhi56
changed the title
gandhi56
changed the title
|
I examined the CI failure thoroughly, there were several warnings as the buildbot was configuring cmake. They all indicated that certain Clang/LLVM library targets were required to be static. The following error was also emitted: The warnings and the above error are orthogonal to this patch. I re-ran the internal PSDB and there were no failures there either. I will merge this PR and hope that the buildbots won't complain this time. |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/10/builds/7773 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/11/builds/17767 Here is the relevant piece of the build log for the reference |
|
Hi @gandhi56, it seems this PR failed test and currently breaks our buildbot. Could you please put up a fix? Thanks! bot: https://lab.llvm.org/buildbot/#/builders/10/builds/7773 |
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I will take care of it this weekend. Thanks for the ping. |
|
Thanks! It would be appreciated if you could revert this one while investigating. It will unblock the downstream merge. |
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…Replacer" (#145137) Reverts llvm/llvm-project#144626
Jaddyen
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This patch enhances the PtrReplacer as follows: 1. Users are now collected iteratively to be generous on the stack. In the case of PHIs with incoming values which have not yet been visited, they are pushed back into the stack for reconsideration. 2. Replace users of the pointer root in a reverse-postorder traversal, instead of a simpletraversal over the collected users. This reordering ensures that the uses of an instruction are replaced before replacing the instruction itself. 3. During the replacement of PHI, use the same incoming value if it does not have a replacement. This patch specifically fixes the case when an incoming value of a PHI is addrspacecasted. This is a reland of llvm#137215.
Jaddyen
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This patch enhances the PtrReplacer as follows:
This patch specifically fixes the case when an incoming value of a PHI is addrspacecasted.
This is a reland of #137215.