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[SimpleLoopUnswitch] Don't use BlockFrequencyInfo to skip cold loops #159522

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[SimpleLoopUnswitch] Don't use BlockFrequencyInfo to skip cold loops #159522

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36844e9
[SimpleLoopUnswitch] Don't use BlockFrequencyInfo to skip cold loops
lukel97 Sep 18, 2025
ca43b4b
Fix polly
lukel97 Sep 18, 2025
754f242
Remove preserve-bpi.ll test
lukel97 Sep 18, 2025
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2 changes: 0 additions & 2 deletions llvm/include/llvm/Analysis/LoopAnalysisManager.h
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,6 @@ namespace llvm {

class AAResults;
class AssumptionCache;
class BlockFrequencyInfo;
class DominatorTree;
class Function;
class Loop;
Expand All @@ -58,7 +57,6 @@ struct LoopStandardAnalysisResults {
ScalarEvolution &SE;
TargetLibraryInfo &TLI;
TargetTransformInfo &TTI;
BlockFrequencyInfo *BFI;
MemorySSA *MSSA;
};

Expand Down
15 changes: 5 additions & 10 deletions llvm/include/llvm/Transforms/Scalar/LoopPassManager.h
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Expand Up @@ -404,10 +404,8 @@ class FunctionToLoopPassAdaptor

explicit FunctionToLoopPassAdaptor(std::unique_ptr<PassConceptT> Pass,
bool UseMemorySSA = false,
bool UseBlockFrequencyInfo = false,
bool LoopNestMode = false)
: Pass(std::move(Pass)), UseMemorySSA(UseMemorySSA),
UseBlockFrequencyInfo(UseBlockFrequencyInfo),
LoopNestMode(LoopNestMode) {
LoopCanonicalizationFPM.addPass(LoopSimplifyPass());
LoopCanonicalizationFPM.addPass(LCSSAPass());
Expand All @@ -429,7 +427,6 @@ class FunctionToLoopPassAdaptor
FunctionPassManager LoopCanonicalizationFPM;

bool UseMemorySSA = false;
bool UseBlockFrequencyInfo = false;
const bool LoopNestMode;
};

Expand All @@ -442,8 +439,7 @@ class FunctionToLoopPassAdaptor
/// \c LoopPassManager and the returned adaptor will be in loop-nest mode.
template <typename LoopPassT>
inline FunctionToLoopPassAdaptor
createFunctionToLoopPassAdaptor(LoopPassT &&Pass, bool UseMemorySSA = false,
bool UseBlockFrequencyInfo = false) {
createFunctionToLoopPassAdaptor(LoopPassT &&Pass, bool UseMemorySSA = false) {
if constexpr (is_detected<HasRunOnLoopT, LoopPassT>::value) {
using PassModelT =
detail::PassModel<Loop, LoopPassT, LoopAnalysisManager,
Expand All @@ -453,7 +449,7 @@ createFunctionToLoopPassAdaptor(LoopPassT &&Pass, bool UseMemorySSA = false,
return FunctionToLoopPassAdaptor(
std::unique_ptr<FunctionToLoopPassAdaptor::PassConceptT>(
new PassModelT(std::forward<LoopPassT>(Pass))),
UseMemorySSA, UseBlockFrequencyInfo, false);
UseMemorySSA, false);
} else {
LoopPassManager LPM;
LPM.addPass(std::forward<LoopPassT>(Pass));
Expand All @@ -465,7 +461,7 @@ createFunctionToLoopPassAdaptor(LoopPassT &&Pass, bool UseMemorySSA = false,
return FunctionToLoopPassAdaptor(
std::unique_ptr<FunctionToLoopPassAdaptor::PassConceptT>(
new PassModelT(std::move(LPM))),
UseMemorySSA, UseBlockFrequencyInfo, true);
UseMemorySSA, true);
}
}

Expand All @@ -474,8 +470,7 @@ createFunctionToLoopPassAdaptor(LoopPassT &&Pass, bool UseMemorySSA = false,
template <>
inline FunctionToLoopPassAdaptor
createFunctionToLoopPassAdaptor<LoopPassManager>(LoopPassManager &&LPM,
bool UseMemorySSA,
bool UseBlockFrequencyInfo) {
bool UseMemorySSA) {
// Check if LPM contains any loop pass and if it does not, returns an adaptor
// in loop-nest mode.
using PassModelT =
Expand All @@ -487,7 +482,7 @@ createFunctionToLoopPassAdaptor<LoopPassManager>(LoopPassManager &&LPM,
return FunctionToLoopPassAdaptor(
std::unique_ptr<FunctionToLoopPassAdaptor::PassConceptT>(
new PassModelT(std::move(LPM))),
UseMemorySSA, UseBlockFrequencyInfo, LoopNestMode);
UseMemorySSA, LoopNestMode);
}

/// Pass for printing a loop's contents as textual IR.
Expand Down
33 changes: 14 additions & 19 deletions llvm/lib/Passes/PassBuilder.cpp
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Expand Up @@ -1931,23 +1931,22 @@ Error PassBuilder::parseModulePass(ModulePassManager &MPM,
#define LOOPNEST_PASS(NAME, CREATE_PASS) \
if (Name == NAME) { \
MPM.addPass(createModuleToFunctionPassAdaptor( \
createFunctionToLoopPassAdaptor(CREATE_PASS, false, false))); \
createFunctionToLoopPassAdaptor(CREATE_PASS, false))); \
return Error::success(); \
}
#define LOOP_PASS(NAME, CREATE_PASS) \
if (Name == NAME) { \
MPM.addPass(createModuleToFunctionPassAdaptor( \
createFunctionToLoopPassAdaptor(CREATE_PASS, false, false))); \
createFunctionToLoopPassAdaptor(CREATE_PASS, false))); \
return Error::success(); \
}
#define LOOP_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS) \
if (checkParametrizedPassName(Name, NAME)) { \
auto Params = parsePassParameters(PARSER, Name, NAME); \
if (!Params) \
return Params.takeError(); \
MPM.addPass( \
createModuleToFunctionPassAdaptor(createFunctionToLoopPassAdaptor( \
CREATE_PASS(Params.get()), false, false))); \
MPM.addPass(createModuleToFunctionPassAdaptor( \
createFunctionToLoopPassAdaptor(CREATE_PASS(Params.get()), false))); \
return Error::success(); \
}
#include "PassRegistry.def"
Expand Down Expand Up @@ -2046,23 +2045,22 @@ Error PassBuilder::parseCGSCCPass(CGSCCPassManager &CGPM,
#define LOOPNEST_PASS(NAME, CREATE_PASS) \
if (Name == NAME) { \
CGPM.addPass(createCGSCCToFunctionPassAdaptor( \
createFunctionToLoopPassAdaptor(CREATE_PASS, false, false))); \
createFunctionToLoopPassAdaptor(CREATE_PASS, false))); \
return Error::success(); \
}
#define LOOP_PASS(NAME, CREATE_PASS) \
if (Name == NAME) { \
CGPM.addPass(createCGSCCToFunctionPassAdaptor( \
createFunctionToLoopPassAdaptor(CREATE_PASS, false, false))); \
createFunctionToLoopPassAdaptor(CREATE_PASS, false))); \
return Error::success(); \
}
#define LOOP_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS) \
if (checkParametrizedPassName(Name, NAME)) { \
auto Params = parsePassParameters(PARSER, Name, NAME); \
if (!Params) \
return Params.takeError(); \
CGPM.addPass( \
createCGSCCToFunctionPassAdaptor(createFunctionToLoopPassAdaptor( \
CREATE_PASS(Params.get()), false, false))); \
CGPM.addPass(createCGSCCToFunctionPassAdaptor( \
createFunctionToLoopPassAdaptor(CREATE_PASS(Params.get()), false))); \
return Error::success(); \
}
#include "PassRegistry.def"
Expand Down Expand Up @@ -2095,11 +2093,8 @@ Error PassBuilder::parseFunctionPass(FunctionPassManager &FPM,
return Err;
// Add the nested pass manager with the appropriate adaptor.
bool UseMemorySSA = (Name == "loop-mssa");
bool UseBFI = llvm::any_of(InnerPipeline, [](auto Pipeline) {
return Pipeline.Name.contains("simple-loop-unswitch");
});
FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM), UseMemorySSA,
UseBFI));
FPM.addPass(
createFunctionToLoopPassAdaptor(std::move(LPM), UseMemorySSA));
return Error::success();
}
if (Name == "machine-function") {
Expand Down Expand Up @@ -2152,21 +2147,21 @@ Error PassBuilder::parseFunctionPass(FunctionPassManager &FPM,
// The risk is that it may become obsolete if we're not careful.
#define LOOPNEST_PASS(NAME, CREATE_PASS) \
if (Name == NAME) { \
FPM.addPass(createFunctionToLoopPassAdaptor(CREATE_PASS, false, false)); \
FPM.addPass(createFunctionToLoopPassAdaptor(CREATE_PASS, false)); \
return Error::success(); \
}
#define LOOP_PASS(NAME, CREATE_PASS) \
if (Name == NAME) { \
FPM.addPass(createFunctionToLoopPassAdaptor(CREATE_PASS, false, false)); \
FPM.addPass(createFunctionToLoopPassAdaptor(CREATE_PASS, false)); \
return Error::success(); \
}
#define LOOP_PASS_WITH_PARAMS(NAME, CLASS, CREATE_PASS, PARSER, PARAMS) \
if (checkParametrizedPassName(Name, NAME)) { \
auto Params = parsePassParameters(PARSER, Name, NAME); \
if (!Params) \
return Params.takeError(); \
FPM.addPass(createFunctionToLoopPassAdaptor(CREATE_PASS(Params.get()), \
false, false)); \
FPM.addPass( \
createFunctionToLoopPassAdaptor(CREATE_PASS(Params.get()), false)); \
return Error::success(); \
}
#include "PassRegistry.def"
Expand Down
34 changes: 14 additions & 20 deletions llvm/lib/Passes/PassBuilderPipelines.cpp
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Expand Up @@ -517,16 +517,14 @@ PassBuilder::buildO1FunctionSimplificationPipeline(OptimizationLevel Level,
invokeLoopOptimizerEndEPCallbacks(LPM2, Level);

FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM1),
/*UseMemorySSA=*/true,
/*UseBlockFrequencyInfo=*/true));
/*UseMemorySSA=*/true));
FPM.addPass(
SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
FPM.addPass(InstCombinePass());
// The loop passes in LPM2 (LoopFullUnrollPass) do not preserve MemorySSA.
// *All* loop passes must preserve it, in order to be able to use it.
FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM2),
/*UseMemorySSA=*/false,
/*UseBlockFrequencyInfo=*/false));
/*UseMemorySSA=*/false));

// Delete small array after loop unroll.
FPM.addPass(SROAPass(SROAOptions::ModifyCFG));
Expand Down Expand Up @@ -706,17 +704,15 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
invokeLoopOptimizerEndEPCallbacks(LPM2, Level);

FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM1),
/*UseMemorySSA=*/true,
/*UseBlockFrequencyInfo=*/true));
/*UseMemorySSA=*/true));
FPM.addPass(
SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
FPM.addPass(InstCombinePass());
// The loop passes in LPM2 (LoopIdiomRecognizePass, IndVarSimplifyPass,
// LoopDeletionPass and LoopFullUnrollPass) do not preserve MemorySSA.
// *All* loop passes must preserve it, in order to be able to use it.
FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM2),
/*UseMemorySSA=*/false,
/*UseBlockFrequencyInfo=*/false));
/*UseMemorySSA=*/false));

// Delete small array after loop unroll.
FPM.addPass(SROAPass(SROAOptions::ModifyCFG));
Expand Down Expand Up @@ -769,7 +765,7 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
FPM.addPass(createFunctionToLoopPassAdaptor(
LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap,
/*AllowSpeculation=*/true),
/*UseMemorySSA=*/true, /*UseBlockFrequencyInfo=*/false));
/*UseMemorySSA=*/true));

FPM.addPass(CoroElidePass());

Expand Down Expand Up @@ -837,8 +833,7 @@ void PassBuilder::addPostPGOLoopRotation(ModulePassManager &MPM,
createFunctionToLoopPassAdaptor(
LoopRotatePass(EnableLoopHeaderDuplication ||
Level != OptimizationLevel::Oz),
/*UseMemorySSA=*/false,
/*UseBlockFrequencyInfo=*/false),
/*UseMemorySSA=*/false),
PTO.EagerlyInvalidateAnalyses));
}
}
Expand Down Expand Up @@ -1354,8 +1349,7 @@ void PassBuilder::addVectorPasses(OptimizationLevel Level,
LPM.addPass(SimpleLoopUnswitchPass(/* NonTrivial */ Level ==
OptimizationLevel::O3));
ExtraPasses.addPass(
createFunctionToLoopPassAdaptor(std::move(LPM), /*UseMemorySSA=*/true,
/*UseBlockFrequencyInfo=*/true));
createFunctionToLoopPassAdaptor(std::move(LPM), /*UseMemorySSA=*/true));
ExtraPasses.addPass(
SimplifyCFGPass(SimplifyCFGOptions().convertSwitchRangeToICmp(true)));
ExtraPasses.addPass(InstCombinePass());
Expand Down Expand Up @@ -1433,7 +1427,7 @@ void PassBuilder::addVectorPasses(OptimizationLevel Level,
FPM.addPass(createFunctionToLoopPassAdaptor(
LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap,
/*AllowSpeculation=*/true),
/*UseMemorySSA=*/true, /*UseBlockFrequencyInfo=*/false));
/*UseMemorySSA=*/true));

// Now that we've vectorized and unrolled loops, we may have more refined
// alignment information, try to re-derive it here.
Expand Down Expand Up @@ -1510,7 +1504,7 @@ PassBuilder::buildModuleOptimizationPipeline(OptimizationLevel Level,
OptimizePM.addPass(createFunctionToLoopPassAdaptor(
LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap,
/*AllowSpeculation=*/true),
/*USeMemorySSA=*/true, /*UseBlockFrequencyInfo=*/false));
/*USeMemorySSA=*/true));
}

OptimizePM.addPass(Float2IntPass());
Expand Down Expand Up @@ -1550,8 +1544,8 @@ PassBuilder::buildModuleOptimizationPipeline(OptimizationLevel Level,
if (PTO.LoopInterchange)
LPM.addPass(LoopInterchangePass());

OptimizePM.addPass(createFunctionToLoopPassAdaptor(
std::move(LPM), /*UseMemorySSA=*/false, /*UseBlockFrequencyInfo=*/false));
OptimizePM.addPass(
createFunctionToLoopPassAdaptor(std::move(LPM), /*UseMemorySSA=*/false));

// FIXME: This may not be the right place in the pipeline.
// We need to have the data to support the right place.
Expand Down Expand Up @@ -2100,7 +2094,7 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
MainFPM.addPass(createFunctionToLoopPassAdaptor(
LICMPass(PTO.LicmMssaOptCap, PTO.LicmMssaNoAccForPromotionCap,
/*AllowSpeculation=*/true),
/*USeMemorySSA=*/true, /*UseBlockFrequencyInfo=*/false));
/*USeMemorySSA=*/true));

if (RunNewGVN)
MainFPM.addPass(NewGVNPass());
Expand Down Expand Up @@ -2130,8 +2124,8 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
PTO.ForgetAllSCEVInLoopUnroll));
// The loop passes in LPM (LoopFullUnrollPass) do not preserve MemorySSA.
// *All* loop passes must preserve it, in order to be able to use it.
MainFPM.addPass(createFunctionToLoopPassAdaptor(
std::move(LPM), /*UseMemorySSA=*/false, /*UseBlockFrequencyInfo=*/true));
MainFPM.addPass(
createFunctionToLoopPassAdaptor(std::move(LPM), /*UseMemorySSA=*/false));

MainFPM.addPass(LoopDistributePass());

Expand Down
5 changes: 0 additions & 5 deletions llvm/lib/Transforms/Scalar/LoopPassManager.cpp
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Expand Up @@ -8,7 +8,6 @@

#include "llvm/Transforms/Scalar/LoopPassManager.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/MemorySSA.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
Expand Down Expand Up @@ -219,17 +218,13 @@ PreservedAnalyses FunctionToLoopPassAdaptor::run(Function &F,
// Get the analysis results needed by loop passes.
MemorySSA *MSSA =
UseMemorySSA ? (&AM.getResult<MemorySSAAnalysis>(F).getMSSA()) : nullptr;
BlockFrequencyInfo *BFI = UseBlockFrequencyInfo && F.hasProfileData()
? (&AM.getResult<BlockFrequencyAnalysis>(F))
: nullptr;
LoopStandardAnalysisResults LAR = {AM.getResult<AAManager>(F),
AM.getResult<AssumptionAnalysis>(F),
AM.getResult<DominatorTreeAnalysis>(F),
AM.getResult<LoopAnalysis>(F),
AM.getResult<ScalarEvolutionAnalysis>(F),
AM.getResult<TargetLibraryAnalysis>(F),
AM.getResult<TargetIRAnalysis>(F),
BFI,
MSSA};

// Setup the loop analysis manager from its proxy. It is important that
Expand Down
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