[llvm] [LoopUnroll] Remove `UseUpperBound` output parameter from `computeUnrollCount` (NFC) (PR #184526)
Justin Fargnoli via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 4 11:56:21 PST 2026
https://github.com/justinfargnoli updated https://github.com/llvm/llvm-project/pull/184526
>From 4762b815cd83faec1872b0ae3058d834d0e1bb01 Mon Sep 17 00:00:00 2001
From: Justin Fargnoli <jfargnoli at nvidia.com>
Date: Wed, 4 Mar 2026 00:53:26 +0000
Subject: [PATCH] [LoopUnroll] Remove UseUpperBound output parameter from
computeUnrollCount (NFC)
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UseUpperBound was a write-only output parameter — set inside
computeUnrollCount but never read by any caller after the function
returned. Remove it from the signature and all call sites.
In computeUnrollAndJamCount, also drop UseUpperBound from the
ExplicitUnroll condition since it was always false (MaxTripCount is
always passed as 0, and UseUpperBound is only set when MaxTripCount
is nonzero).
Conflirts:
llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
---
.../llvm/Transforms/Utils/UnrollLoop.h | 17 ++++++-----
llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp | 4 +--
.../Scalar/LoopUnrollAndJamPass.cpp | 12 ++++----
llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp | 29 +++++++++----------
4 files changed, 29 insertions(+), 33 deletions(-)
diff --git a/llvm/include/llvm/Transforms/Utils/UnrollLoop.h b/llvm/include/llvm/Transforms/Utils/UnrollLoop.h
index a3efc43c62dc3..c6c691e683b22 100644
--- a/llvm/include/llvm/Transforms/Utils/UnrollLoop.h
+++ b/llvm/include/llvm/Transforms/Utils/UnrollLoop.h
@@ -157,14 +157,15 @@ class UnrollCostEstimator {
unsigned CountOverwrite = 0) const;
};
-LLVM_ABI bool computeUnrollCount(
- Loop *L, const TargetTransformInfo &TTI, DominatorTree &DT, LoopInfo *LI,
- AssumptionCache *AC, ScalarEvolution &SE,
- const SmallPtrSetImpl<const Value *> &EphValues,
- OptimizationRemarkEmitter *ORE, unsigned TripCount, unsigned MaxTripCount,
- bool MaxOrZero, unsigned TripMultiple, const UnrollCostEstimator &UCE,
- TargetTransformInfo::UnrollingPreferences &UP,
- TargetTransformInfo::PeelingPreferences &PP, bool &UseUpperBound);
+LLVM_ABI bool
+computeUnrollCount(Loop *L, const TargetTransformInfo &TTI, DominatorTree &DT,
+ LoopInfo *LI, AssumptionCache *AC, ScalarEvolution &SE,
+ const SmallPtrSetImpl<const Value *> &EphValues,
+ OptimizationRemarkEmitter *ORE, unsigned TripCount,
+ unsigned MaxTripCount, bool MaxOrZero, unsigned TripMultiple,
+ const UnrollCostEstimator &UCE,
+ TargetTransformInfo::UnrollingPreferences &UP,
+ TargetTransformInfo::PeelingPreferences &PP);
LLVM_ABI std::optional<RecurrenceDescriptor>
canParallelizeReductionWhenUnrolling(PHINode &Phi, Loop *L,
diff --git a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
index 9035ae7796a2e..1d522e9b14c7a 100644
--- a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
+++ b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
@@ -7110,10 +7110,8 @@ static int32_t computeHeuristicUnrollFactor(CanonicalLoopInfo *CLI) {
bool MaxOrZero = false;
unsigned TripMultiple = 0;
- bool UseUpperBound = false;
computeUnrollCount(L, TTI, DT, &LI, &AC, SE, EphValues, &ORE, TripCount,
- MaxTripCount, MaxOrZero, TripMultiple, UCE, UP, PP,
- UseUpperBound);
+ MaxTripCount, MaxOrZero, TripMultiple, UCE, UP, PP);
unsigned Factor = UP.Count;
LLVM_DEBUG(dbgs() << "Suggesting unroll factor of " << Factor << "\n");
diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp
index 4fe74c7c3bbcd..1121690dbbb69 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp
@@ -162,13 +162,11 @@ static bool computeUnrollAndJamCount(
// unrolling we leave to the unroller. This uses UP.Threshold /
// UP.PartialThreshold / UP.MaxCount to come up with sensible loop values.
// We have already checked that the loop has no unroll.* pragmas.
- unsigned MaxTripCount = 0;
- bool UseUpperBound = false;
- bool ExplicitUnroll = computeUnrollCount(
- L, TTI, DT, LI, AC, SE, EphValues, ORE, OuterTripCount, MaxTripCount,
- /*MaxOrZero*/ false, OuterTripMultiple, OuterUCE, UP, PP,
- UseUpperBound);
- if (ExplicitUnroll || UseUpperBound) {
+ bool ExplicitUnroll =
+ computeUnrollCount(L, TTI, DT, LI, AC, SE, EphValues, ORE, OuterTripCount,
+ /*MaxTripCount*/ 0, /*MaxOrZero*/ false,
+ OuterTripMultiple, OuterUCE, UP, PP);
+ if (ExplicitUnroll) {
// If the user explicitly set the loop as unrolled, dont UnJ it. Leave it
// for the unroller instead.
LLVM_DEBUG(dbgs() << "Won't unroll-and-jam; explicit count set by "
diff --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index 4af57ff7697f7..3479115de8702 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -932,15 +932,17 @@ shouldPartialUnroll(const unsigned LoopSize, const unsigned TripCount,
// FIXME: This function is used by LoopUnroll and LoopUnrollAndJam, but consumes
// many LoopUnroll-specific options. The shared functionality should be
// refactored into it own function.
-bool llvm::computeUnrollCount(
- Loop *L, const TargetTransformInfo &TTI, DominatorTree &DT, LoopInfo *LI,
- AssumptionCache *AC, ScalarEvolution &SE,
- const SmallPtrSetImpl<const Value *> &EphValues,
- OptimizationRemarkEmitter *ORE, const unsigned TripCount,
- const unsigned MaxTripCount, const bool MaxOrZero,
- const unsigned TripMultiple, const UnrollCostEstimator &UCE,
- TargetTransformInfo::UnrollingPreferences &UP,
- TargetTransformInfo::PeelingPreferences &PP, bool &UseUpperBound) {
+bool llvm::computeUnrollCount(Loop *L, const TargetTransformInfo &TTI,
+ DominatorTree &DT, LoopInfo *LI,
+ AssumptionCache *AC, ScalarEvolution &SE,
+ const SmallPtrSetImpl<const Value *> &EphValues,
+ OptimizationRemarkEmitter *ORE,
+ const unsigned TripCount,
+ const unsigned MaxTripCount, const bool MaxOrZero,
+ const unsigned TripMultiple,
+ const UnrollCostEstimator &UCE,
+ TargetTransformInfo::UnrollingPreferences &UP,
+ TargetTransformInfo::PeelingPreferences &PP) {
unsigned LoopSize = UCE.getRolledLoopSize();
@@ -997,7 +999,6 @@ bool llvm::computeUnrollCount(
if (auto UnrollFactor = shouldFullUnroll(L, TTI, DT, SE, EphValues,
TripCount, UCE, UP)) {
UP.Count = *UnrollFactor;
- UseUpperBound = false;
return ExplicitUnroll;
}
}
@@ -1020,7 +1021,6 @@ bool llvm::computeUnrollCount(
if (auto UnrollFactor = shouldFullUnroll(L, TTI, DT, SE, EphValues,
MaxTripCount, UCE, UP)) {
UP.Count = *UnrollFactor;
- UseUpperBound = true;
return ExplicitUnroll;
}
}
@@ -1304,10 +1304,9 @@ tryToUnrollLoop(Loop *L, DominatorTree &DT, LoopInfo *LI, ScalarEvolution &SE,
// computeUnrollCount() decides whether it is beneficial to use upper bound to
// fully unroll the loop.
- bool UseUpperBound = false;
- bool IsCountSetExplicitly = computeUnrollCount(
- L, TTI, DT, LI, &AC, SE, EphValues, &ORE, TripCount, MaxTripCount,
- MaxOrZero, TripMultiple, UCE, UP, PP, UseUpperBound);
+ bool IsCountSetExplicitly =
+ computeUnrollCount(L, TTI, DT, LI, &AC, SE, EphValues, &ORE, TripCount,
+ MaxTripCount, MaxOrZero, TripMultiple, UCE, UP, PP);
if (!UP.Count)
return LoopUnrollResult::Unmodified;
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