[llvm] 1828312 - [Attributor] Add AAExecutionDomainInfo interface to OpenMPOpt
Joseph Huber via llvm-commits
llvm-commits at lists.llvm.org
Mon May 3 16:24:49 PDT 2021
Author: Joseph Huber
Date: 2021-05-03T19:24:19-04:00
New Revision: 182831258bfe520140956a4da6c8c6177d37299a
URL: https://github.com/llvm/llvm-project/commit/182831258bfe520140956a4da6c8c6177d37299a
DIFF: https://github.com/llvm/llvm-project/commit/182831258bfe520140956a4da6c8c6177d37299a.diff
LOG: [Attributor] Add AAExecutionDomainInfo interface to OpenMPOpt
Summary:
Add the AAExecutionDomainInfo attributor instance to OpenMPOpt.
This will infer information relating to domain information that an
instruction might be expecting in. Right now this only includes a very
crude check for instructions that will be executed by the master thread
by comparing a thread-id function with a constant zero.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D101578
Added:
llvm/test/Transforms/OpenMP/single_threaded_execution.ll
Modified:
llvm/lib/Transforms/IPO/OpenMPOpt.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/IPO/OpenMPOpt.cpp b/llvm/lib/Transforms/IPO/OpenMPOpt.cpp
index e2b277e3b5b90..4ea2e848e3903 100644
--- a/llvm/lib/Transforms/IPO/OpenMPOpt.cpp
+++ b/llvm/lib/Transforms/IPO/OpenMPOpt.cpp
@@ -15,6 +15,7 @@
#include "llvm/Transforms/IPO/OpenMPOpt.h"
#include "llvm/ADT/EnumeratedArray.h"
+#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/CallGraphSCCPass.h"
@@ -78,6 +79,36 @@ static constexpr auto TAG = "[" DEBUG_TYPE "]";
namespace {
+struct AAExecutionDomain
+ : public StateWrapper<BooleanState, AbstractAttribute> {
+ using Base = StateWrapper<BooleanState, AbstractAttribute>;
+ AAExecutionDomain(const IRPosition &IRP, Attributor &A) : Base(IRP) {}
+
+ /// Create an abstract attribute view for the position \p IRP.
+ static AAExecutionDomain &createForPosition(const IRPosition &IRP,
+ Attributor &A);
+
+ /// See AbstractAttribute::getName().
+ const std::string getName() const override { return "AAExecutionDomain"; }
+
+ /// See AbstractAttribute::getIdAddr().
+ const char *getIdAddr() const override { return &ID; }
+
+ /// Check if an instruction is executed by a single thread.
+ virtual bool isSingleThreadExecution(const Instruction &) const = 0;
+
+ virtual bool isSingleThreadExecution(const BasicBlock &) const = 0;
+
+ /// This function should return true if the type of the \p AA is
+ /// AAExecutionDomain.
+ static bool classof(const AbstractAttribute *AA) {
+ return (AA->getIdAddr() == &ID);
+ }
+
+ /// Unique ID (due to the unique address)
+ static const char ID;
+};
+
struct AAICVTracker;
/// OpenMP specific information. For now, stores RFIs and ICVs also needed for
@@ -506,6 +537,8 @@ struct OpenMPOpt {
<< OMPInfoCache.ModuleSlice.size() << " functions\n");
if (IsModulePass) {
+ Changed |= runAttributor();
+
if (remarksEnabled())
analysisGlobalization();
} else {
@@ -1606,6 +1639,11 @@ struct OpenMPOpt {
GetterRFI.foreachUse(SCC, CreateAA);
}
+
+ for (auto &F : M) {
+ if (!F.isDeclaration())
+ A.getOrCreateAAFor<AAExecutionDomain>(IRPosition::function(F));
+ }
}
};
@@ -2244,9 +2282,136 @@ struct AAICVTrackerCallSiteReturned : AAICVTracker {
return Changed;
}
};
+
+struct AAExecutionDomainFunction : public AAExecutionDomain {
+ AAExecutionDomainFunction(const IRPosition &IRP, Attributor &A)
+ : AAExecutionDomain(IRP, A) {}
+
+ const std::string getAsStr() const override {
+ return "[AAExecutionDomain] " + std::to_string(SingleThreadedBBs.size()) +
+ "/" + std::to_string(NumBBs) + " BBs thread 0 only.";
+ }
+
+ /// See AbstractAttribute::trackStatistics().
+ void trackStatistics() const override {}
+
+ void initialize(Attributor &A) override {
+ Function *F = getAnchorScope();
+ for (const auto &BB : *F)
+ SingleThreadedBBs.insert(&BB);
+ NumBBs = SingleThreadedBBs.size();
+ }
+
+ ChangeStatus manifest(Attributor &A) override {
+ LLVM_DEBUG({
+ for (const BasicBlock *BB : SingleThreadedBBs)
+ dbgs() << TAG << " Basic block @" << getAnchorScope()->getName() << " "
+ << BB->getName() << " is executed by a single thread.\n";
+ });
+ return ChangeStatus::UNCHANGED;
+ }
+
+ ChangeStatus updateImpl(Attributor &A) override;
+
+ /// Check if an instruction is executed by a single thread.
+ bool isSingleThreadExecution(const Instruction &I) const override {
+ return isSingleThreadExecution(*I.getParent());
+ }
+
+ bool isSingleThreadExecution(const BasicBlock &BB) const override {
+ return SingleThreadedBBs.contains(&BB);
+ }
+
+ /// Set of basic blocks that are executed by a single thread.
+ DenseSet<const BasicBlock *> SingleThreadedBBs;
+
+ /// Total number of basic blocks in this function.
+ long unsigned NumBBs;
+};
+
+ChangeStatus AAExecutionDomainFunction::updateImpl(Attributor &A) {
+ auto &OMPInfoCache = static_cast<OMPInformationCache &>(A.getInfoCache());
+ Function *F = getAnchorScope();
+ ReversePostOrderTraversal<Function *> RPOT(F);
+ auto NumSingleThreadedBBs = SingleThreadedBBs.size();
+
+ bool AllCallSitesKnown;
+ auto PredForCallSite = [&](AbstractCallSite ACS) {
+ const auto &ExecutionDomainAA = A.getAAFor<AAExecutionDomain>(
+ *this, IRPosition::function(*ACS.getInstruction()->getFunction()),
+ DepClassTy::REQUIRED);
+ return ExecutionDomainAA.isSingleThreadExecution(*ACS.getInstruction());
+ };
+
+ if (!A.checkForAllCallSites(PredForCallSite, *this,
+ /* RequiresAllCallSites */ true,
+ AllCallSitesKnown))
+ SingleThreadedBBs.erase(&F->getEntryBlock());
+
+ // Check if the edge into the successor block compares a thread-id function to
+ // a constant zero.
+ // TODO: Use AAValueSimplify to simplify and propogate constants.
+ // TODO: Check more than a single use for thread ID's.
+ auto IsSingleThreadOnly = [&](BranchInst *Edge, BasicBlock *SuccessorBB) {
+ if (!Edge || !Edge->isConditional())
+ return false;
+ if (Edge->getSuccessor(0) != SuccessorBB)
+ return false;
+
+ auto *Cmp = dyn_cast<CmpInst>(Edge->getCondition());
+ if (!Cmp || !Cmp->isTrueWhenEqual() || !Cmp->isEquality())
+ return false;
+
+ ConstantInt *C = dyn_cast<ConstantInt>(Cmp->getOperand(1));
+ if (!C || !C->isZero())
+ return false;
+
+ if (auto *CB = dyn_cast<CallBase>(Cmp->getOperand(0))) {
+ RuntimeFunction ThreadNumRuntimeIDs[] = {OMPRTL_omp_get_thread_num,
+ OMPRTL___kmpc_master,
+ OMPRTL___kmpc_global_thread_num};
+
+ for (const auto ThreadNumRuntimeID : ThreadNumRuntimeIDs) {
+ auto &RFI = OMPInfoCache.RFIs[ThreadNumRuntimeID];
+ if (CB->getCalledFunction() == RFI.Declaration)
+ return true;
+ }
+ }
+
+ return false;
+ };
+
+ // Merge all the predecessor states into the current basic block. A basic
+ // block is executed by a single thread if all of its predecessors are.
+ auto MergePredecessorStates = [&](BasicBlock *BB) {
+ if (pred_begin(BB) == pred_end(BB))
+ return SingleThreadedBBs.contains(BB);
+
+ bool IsSingleThreaded = true;
+ for (auto PredBB = pred_begin(BB), PredEndBB = pred_end(BB);
+ PredBB != PredEndBB; ++PredBB) {
+ if (!IsSingleThreadOnly(dyn_cast<BranchInst>((*PredBB)->getTerminator()),
+ BB))
+ IsSingleThreaded &= SingleThreadedBBs.contains(*PredBB);
+ }
+
+ return IsSingleThreaded;
+ };
+
+ for (auto *BB : RPOT) {
+ if (!MergePredecessorStates(BB))
+ SingleThreadedBBs.erase(BB);
+ }
+
+ return (NumSingleThreadedBBs == SingleThreadedBBs.size())
+ ? ChangeStatus::UNCHANGED
+ : ChangeStatus::CHANGED;
+}
+
} // namespace
const char AAICVTracker::ID = 0;
+const char AAExecutionDomain::ID = 0;
AAICVTracker &AAICVTracker::createForPosition(const IRPosition &IRP,
Attributor &A) {
@@ -2274,6 +2439,27 @@ AAICVTracker &AAICVTracker::createForPosition(const IRPosition &IRP,
return *AA;
}
+AAExecutionDomain &AAExecutionDomain::createForPosition(const IRPosition &IRP,
+ Attributor &A) {
+ AAExecutionDomainFunction *AA = nullptr;
+ switch (IRP.getPositionKind()) {
+ case IRPosition::IRP_INVALID:
+ case IRPosition::IRP_FLOAT:
+ case IRPosition::IRP_ARGUMENT:
+ case IRPosition::IRP_CALL_SITE_ARGUMENT:
+ case IRPosition::IRP_RETURNED:
+ case IRPosition::IRP_CALL_SITE_RETURNED:
+ case IRPosition::IRP_CALL_SITE:
+ llvm_unreachable(
+ "AAExecutionDomain can only be created for function position!");
+ case IRPosition::IRP_FUNCTION:
+ AA = new (A.Allocator) AAExecutionDomainFunction(IRP, A);
+ break;
+ }
+
+ return *AA;
+}
+
PreservedAnalyses OpenMPOptPass::run(Module &M, ModuleAnalysisManager &AM) {
if (!containsOpenMP(M, OMPInModule))
return PreservedAnalyses::all();
diff --git a/llvm/test/Transforms/OpenMP/single_threaded_execution.ll b/llvm/test/Transforms/OpenMP/single_threaded_execution.ll
new file mode 100644
index 0000000000000..acafadbfd702c
--- /dev/null
+++ b/llvm/test/Transforms/OpenMP/single_threaded_execution.ll
@@ -0,0 +1,43 @@
+; RUN: opt -passes=openmp-opt-cgscc -debug-only=openmp-opt -disable-output < %s 2>&1 | FileCheck %s
+; ModuleID = 'single_threaded_exeuction.c'
+
+%struct.ident_t = type { i32, i32, i32, i32, i8* }
+
+ at .str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
+ at 0 = private unnamed_addr constant [23 x i8] c";unknown;unknown;0;0;;\00", align 1
+ at 1 = private unnamed_addr constant %struct.ident_t { i32 0, i32 2, i32 0, i32 0, i8* getelementptr inbounds ([23 x i8], [23 x i8]* @0, i32 0, i32 0) }, align 8
+
+; CHECK: [openmp-opt] Basic block @bar entry is executed by a single thread.
+; Function Attrs: noinline nounwind uwtable
+define internal void @bar() {
+entry:
+ ret void
+}
+
+; CHECK-NOT: [openmp-opt] Basic block @foo entry is executed by a single thread.
+; CHECK: [openmp-opt] Basic block @foo if.then is executed by a single thread.
+; CHECK-NOT: [openmp-opt] Basic block @foo if.end is executed by a single thread.
+; Function Attrs: noinline nounwind uwtable
+define dso_local void @foo() {
+entry:
+ %call = call i32 @omp_get_thread_num()
+ %cmp = icmp eq i32 %call, 0
+ br i1 %cmp, label %if.then, label %if.end
+
+if.then:
+ call void @bar()
+ br label %if.end
+
+if.end:
+ ret void
+}
+
+declare dso_local i32 @omp_get_thread_num()
+
+!llvm.module.flags = !{!0}
+!llvm.ident = !{!1}
+
+!0 = !{i32 1, !"wchar_size", i32 4}
+!1 = !{!"clang version 13.0.0"}
+!2 = !{!3}
+!3 = !{i64 2, i64 -1, i64 -1, i1 true}
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