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[Arm] Control forced unrolling of small loops #170127

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[Arm] Control forced unrolling of small loops #170127

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d628aaf
[Arm] Control forced unrolling of small loops
VladiKrapp-Arm Dec 1, 2025
a3fe6a4
Merge branch 'main' into arm_force_unroll_flag
VladiKrapp-Arm Dec 1, 2025
3900d2a
Merge branch 'main' into arm_force_unroll_flag
VladiKrapp-Arm Dec 1, 2025
70f9df6
Merge branch 'main' into arm_force_unroll_flag
VladiKrapp-Arm Dec 1, 2025
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7 changes: 6 additions & 1 deletion llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,11 @@ extern cl::opt<bool> EnableMaskedGatherScatters;

extern cl::opt<unsigned> MVEMaxSupportedInterleaveFactor;

static cl::opt<int> ArmForceUnrollThreshold(
"arm-force-unroll-threshold", cl::init(12), cl::Hidden,
cl::desc(
"Threshold for forced unrolling of small loops in Arm architecture"));

/// Convert a vector load intrinsic into a simple llvm load instruction.
/// This is beneficial when the underlying object being addressed comes
/// from a constant, since we get constant-folding for free.
Expand Down Expand Up @@ -2731,7 +2736,7 @@ void ARMTTIImpl::getUnrollingPreferences(Loop *L, ScalarEvolution &SE,

// Force unrolling small loops can be very useful because of the branch
// taken cost of the backedge.
if (Cost < 12)
if (Cost < ArmForceUnrollThreshold)
UP.Force = true;
}

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