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[GVN] MemorySSA for GVN: add optional AllowMemorySSA #120982

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Merged
merged 1 commit into from
Jan 10, 2025
Merged

[GVN] MemorySSA for GVN: add optional AllowMemorySSA #120982

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13 changes: 10 additions & 3 deletions llvm/include/llvm/Transforms/Scalar/GVN.h
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Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,7 @@ struct GVNOptions {
std::optional<bool> AllowLoadInLoopPRE;
std::optional<bool> AllowLoadPRESplitBackedge;
std::optional<bool> AllowMemDep;
std::optional<bool> AllowMemorySSA;

GVNOptions() = default;

Expand Down Expand Up @@ -108,6 +109,12 @@ struct GVNOptions {
AllowMemDep = MemDep;
return *this;
}

/// Enables or disables use of MemorySSA.
GVNOptions &setMemorySSA(bool MemSSA) {
AllowMemorySSA = MemSSA;
return *this;
}
};

/// The core GVN pass object.
Expand Down Expand Up @@ -144,6 +151,7 @@ class GVNPass : public PassInfoMixin<GVNPass> {
bool isLoadInLoopPREEnabled() const;
bool isLoadPRESplitBackedgeEnabled() const;
bool isMemDepEnabled() const;
bool isMemorySSAEnabled() const;

/// This class holds the mapping between values and value numbers. It is used
/// as an efficient mechanism to determine the expression-wise equivalence of
Expand Down Expand Up @@ -383,9 +391,8 @@ class GVNPass : public PassInfoMixin<GVNPass> {
void assignBlockRPONumber(Function &F);
};

/// Create a legacy GVN pass. This also allows parameterizing whether or not
/// MemDep is enabled.
FunctionPass *createGVNPass(bool NoMemDepAnalysis = false);
/// Create a legacy GVN pass.
FunctionPass *createGVNPass();

/// A simple and fast domtree-based GVN pass to hoist common expressions
/// from sibling branches.
Expand Down
2 changes: 2 additions & 0 deletions llvm/lib/Passes/PassBuilder.cpp
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Expand Up @@ -1042,6 +1042,8 @@ Expected<GVNOptions> parseGVNOptions(StringRef Params) {
Result.setLoadPRESplitBackedge(Enable);
} else if (ParamName == "memdep") {
Result.setMemDep(Enable);
} else if (ParamName == "memoryssa") {
Result.setMemorySSA(Enable);
} else {
return make_error<StringError>(
formatv("invalid GVN pass parameter '{0}' ", ParamName).str(),
Expand Down
2 changes: 1 addition & 1 deletion llvm/lib/Passes/PassRegistry.def
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Expand Up @@ -526,7 +526,7 @@ FUNCTION_PASS_WITH_PARAMS(
"gvn", "GVNPass", [](GVNOptions Opts) { return GVNPass(Opts); },
parseGVNOptions,
"no-pre;pre;no-load-pre;load-pre;no-split-backedge-load-pre;"
"split-backedge-load-pre;no-memdep;memdep")
"split-backedge-load-pre;no-memdep;memdep;no-memoryssa;memoryssa")
FUNCTION_PASS_WITH_PARAMS(
"hardware-loops", "HardwareLoopsPass",
[](HardwareLoopOptions Opts) { return HardwareLoopsPass(Opts); },
Expand Down
35 changes: 25 additions & 10 deletions llvm/lib/Transforms/Scalar/GVN.cpp
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Expand Up @@ -113,6 +113,8 @@ static cl::opt<bool>
GVNEnableSplitBackedgeInLoadPRE("enable-split-backedge-in-load-pre",
cl::init(false));
static cl::opt<bool> GVNEnableMemDep("enable-gvn-memdep", cl::init(true));
static cl::opt<bool> GVNEnableMemorySSA("enable-gvn-memoryssa",
cl::init(false));

static cl::opt<uint32_t> MaxNumDeps(
"gvn-max-num-deps", cl::Hidden, cl::init(100),
Expand Down Expand Up @@ -820,6 +822,10 @@ bool GVNPass::isMemDepEnabled() const {
return Options.AllowMemDep.value_or(GVNEnableMemDep);
}

bool GVNPass::isMemorySSAEnabled() const {
return Options.AllowMemorySSA.value_or(GVNEnableMemorySSA);
}

PreservedAnalyses GVNPass::run(Function &F, FunctionAnalysisManager &AM) {
// FIXME: The order of evaluation of these 'getResult' calls is very
// significant! Re-ordering these variables will cause GVN when run alone to
Expand All @@ -832,7 +838,10 @@ PreservedAnalyses GVNPass::run(Function &F, FunctionAnalysisManager &AM) {
auto *MemDep =
isMemDepEnabled() ? &AM.getResult<MemoryDependenceAnalysis>(F) : nullptr;
auto &LI = AM.getResult<LoopAnalysis>(F);
auto *MSSA = AM.getCachedResult<MemorySSAAnalysis>(F);
auto *MSSA =
isMemorySSAEnabled() ? &AM.getResult<MemorySSAAnalysis>(F) : nullptr;
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@nikic nikic Jan 10, 2025

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The change here means that we no longer try to update and preserve an already computed MSSA instance. I've reverted this patch for now.

assert(!(MemDep && MSSA) &&
"Should not use both MemDep and MemorySSA simultaneously!");
auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
bool Changed = runImpl(F, AC, DT, TLI, AA, MemDep, LI, &ORE,
MSSA ? &MSSA->getMSSA() : nullptr);
Expand Down Expand Up @@ -861,7 +870,9 @@ void GVNPass::printPipeline(
OS << (*Options.AllowLoadPRESplitBackedge ? "" : "no-")
<< "split-backedge-load-pre;";
if (Options.AllowMemDep != std::nullopt)
OS << (*Options.AllowMemDep ? "" : "no-") << "memdep";
OS << (*Options.AllowMemDep ? "" : "no-") << "memdep;";
if (Options.AllowMemorySSA != std::nullopt)
OS << (*Options.AllowMemorySSA ? "" : "no-") << "memoryssa";
OS << '>';
}

Expand Down Expand Up @@ -3293,16 +3304,18 @@ class llvm::gvn::GVNLegacyPass : public FunctionPass {
public:
static char ID; // Pass identification, replacement for typeid

explicit GVNLegacyPass(bool NoMemDepAnalysis = !GVNEnableMemDep)
: FunctionPass(ID), Impl(GVNOptions().setMemDep(!NoMemDepAnalysis)) {
explicit GVNLegacyPass(bool MemDepAnalysis = GVNEnableMemDep,
bool MemSSAAnalysis = GVNEnableMemorySSA)
: FunctionPass(ID), Impl(GVNOptions()
.setMemDep(MemDepAnalysis)
.setMemorySSA(MemSSAAnalysis)) {
initializeGVNLegacyPassPass(*PassRegistry::getPassRegistry());
}

bool runOnFunction(Function &F) override {
if (skipFunction(F))
return false;

auto *MSSAWP = getAnalysisIfAvailable<MemorySSAWrapperPass>();
return Impl.runImpl(
F, getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F),
getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
Expand All @@ -3313,7 +3326,9 @@ class llvm::gvn::GVNLegacyPass : public FunctionPass {
: nullptr,
getAnalysis<LoopInfoWrapperPass>().getLoopInfo(),
&getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE(),
MSSAWP ? &MSSAWP->getMSSA() : nullptr);
Impl.isMemorySSAEnabled()
? &getAnalysis<MemorySSAWrapperPass>().getMSSA()
: nullptr);
}

void getAnalysisUsage(AnalysisUsage &AU) const override {
Expand All @@ -3329,7 +3344,8 @@ class llvm::gvn::GVNLegacyPass : public FunctionPass {
AU.addPreserved<TargetLibraryInfoWrapperPass>();
AU.addPreserved<LoopInfoWrapperPass>();
AU.addRequired<OptimizationRemarkEmitterWrapperPass>();
AU.addPreserved<MemorySSAWrapperPass>();
if (Impl.isMemorySSAEnabled())
AU.addRequired<MemorySSAWrapperPass>();
}

private:
Expand All @@ -3341,6 +3357,7 @@ char GVNLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(GVNLegacyPass, "gvn", "Global Value Numbering", false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(MemoryDependenceWrapperPass)
INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
Expand All @@ -3349,6 +3366,4 @@ INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass)
INITIALIZE_PASS_END(GVNLegacyPass, "gvn", "Global Value Numbering", false, false)

// The public interface to this file...
FunctionPass *llvm::createGVNPass(bool NoMemDepAnalysis) {
return new GVNLegacyPass(NoMemDepAnalysis);
}
FunctionPass *llvm::createGVNPass() { return new GVNLegacyPass(); }
4 changes: 2 additions & 2 deletions llvm/test/Other/new-pm-print-pipeline.ll
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Expand Up @@ -31,8 +31,8 @@
; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='function(loop-unroll<>,loop-unroll<partial;peeling;runtime;upperbound;profile-peeling;full-unroll-max=5;O1>,loop-unroll<no-partial;no-peeling;no-runtime;no-upperbound;no-profile-peeling;full-unroll-max=7;O1>)' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-10
; CHECK-10: function(loop-unroll<O2>,loop-unroll<partial;peeling;runtime;upperbound;profile-peeling;full-unroll-max=5;O1>,loop-unroll<no-partial;no-peeling;no-runtime;no-upperbound;no-profile-peeling;full-unroll-max=7;O1>)

; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='function(gvn<>,gvn<pre;load-pre;split-backedge-load-pre;memdep>,gvn<no-pre;no-load-pre;no-split-backedge-load-pre;no-memdep>)' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-11
; CHECK-11: function(gvn<>,gvn<pre;load-pre;split-backedge-load-pre;memdep>,gvn<no-pre;no-load-pre;no-split-backedge-load-pre;no-memdep>)
; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='function(gvn<>,gvn<pre;load-pre;split-backedge-load-pre;memdep;memoryssa>,gvn<no-pre;no-load-pre;no-split-backedge-load-pre;no-memdep;no-memoryssa>)' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-11
; CHECK-11: function(gvn<>,gvn<pre;load-pre;split-backedge-load-pre;memdep;memoryssa>,gvn<no-pre;no-load-pre;no-split-backedge-load-pre;no-memdep;no-memoryssa>)

; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='function(early-cse<>,early-cse<memssa>)' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-12
; CHECK-12: function(early-cse<>,early-cse<memssa>)
Expand Down
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