[llvm] [CalcSpillWeights] Simplify copy hint register collection. NFC. (PR #114236)
Valery Pykhtin via llvm-commits
llvm-commits at lists.llvm.org
Fri Nov 1 02:40:13 PDT 2024
https://github.com/vpykhtin updated https://github.com/llvm/llvm-project/pull/114236
>From 06e5544b95995cbec59406a406fa3c9284602ab7 Mon Sep 17 00:00:00 2001
From: Valery Pykhtin <valery.pykhtin at gmail.com>
Date: Thu, 31 Oct 2024 08:39:03 +0100
Subject: [PATCH 1/2] [CalcSpillWeights] Simplify copy hint register
collection. NFC.
---
llvm/lib/CodeGen/CalcSpillWeights.cpp | 56 +++++++++++----------------
1 file changed, 22 insertions(+), 34 deletions(-)
diff --git a/llvm/lib/CodeGen/CalcSpillWeights.cpp b/llvm/lib/CodeGen/CalcSpillWeights.cpp
index f361c956092e88..baa4dec9075e1a 100644
--- a/llvm/lib/CodeGen/CalcSpillWeights.cpp
+++ b/llvm/lib/CodeGen/CalcSpillWeights.cpp
@@ -207,24 +207,8 @@ float VirtRegAuxInfo::weightCalcHelper(LiveInterval &LI, SlotIndex *Start,
NumInstr += 2;
}
- // CopyHint is a sortable hint derived from a COPY instruction.
- struct CopyHint {
- const Register Reg;
- const float Weight;
- CopyHint(Register R, float W) : Reg(R), Weight(W) {}
- bool operator<(const CopyHint &Rhs) const {
- // Always prefer any physreg hint.
- if (Reg.isPhysical() != Rhs.Reg.isPhysical())
- return Reg.isPhysical();
- if (Weight != Rhs.Weight)
- return (Weight > Rhs.Weight);
- return Reg.id() < Rhs.Reg.id(); // Tie-breaker.
- }
- };
-
bool IsExiting = false;
- std::set<CopyHint> CopyHints;
- SmallDenseMap<unsigned, float, 8> Hint;
+ SmallDenseMap<Register, float, 8> Hint;
for (MachineRegisterInfo::reg_instr_nodbg_iterator
I = MRI.reg_instr_nodbg_begin(LI.reg()),
E = MRI.reg_instr_nodbg_end();
@@ -260,8 +244,7 @@ float VirtRegAuxInfo::weightCalcHelper(LiveInterval &LI, SlotIndex *Start,
return -1.0f;
}
- // Force Weight onto the stack so that x86 doesn't add hidden precision,
- // similar to HWeight below.
+ // Force Weight onto the stack so that x86 doesn't add hidden precision.
stack_float_t Weight = 1.0f;
if (IsSpillable) {
// Get loop info for mi.
@@ -287,29 +270,34 @@ float VirtRegAuxInfo::weightCalcHelper(LiveInterval &LI, SlotIndex *Start,
if (!TII.isCopyInstr(*MI))
continue;
Register HintReg = copyHint(MI, LI.reg(), TRI, MRI);
- if (!HintReg)
- continue;
- // Force HWeight onto the stack so that x86 doesn't add hidden precision,
- // making the comparison incorrectly pass (i.e., 1 > 1 == true??).
- stack_float_t HWeight = Hint[HintReg] += Weight;
- if (HintReg.isVirtual() || MRI.isAllocatable(HintReg))
- CopyHints.insert(CopyHint(HintReg, HWeight));
+ if (HintReg && (HintReg.isVirtual() || MRI.isAllocatable(HintReg)))
+ Hint[HintReg] += Weight;
}
// Pass all the sorted copy hints to mri.
- if (ShouldUpdateLI && CopyHints.size()) {
+ if (ShouldUpdateLI && Hint.size()) {
// Remove a generic hint if previously added by target.
if (TargetHint.first == 0 && TargetHint.second)
MRI.clearSimpleHint(LI.reg());
- SmallSet<Register, 4> HintedRegs;
- for (const auto &Hint : CopyHints) {
- if (!HintedRegs.insert(Hint.Reg).second ||
- (TargetHint.first != 0 && Hint.Reg == TargetHint.second))
- // Don't add the same reg twice or the target-type hint again.
- continue;
- MRI.addRegAllocationHint(LI.reg(), Hint.Reg);
+ // Don't add the target-type hint again.
+ Register SkipReg = TargetHint.first != 0 ? TargetHint.second : Register();
+ SmallVector<std::pair<float, Register>, 4> FRegHints, VRegHints;
+ for (const auto &[Reg, Weight] : Hint) {
+ if (Reg != SkipReg)
+ (Reg.isPhysical() ? &FRegHints : &VRegHints)->emplace_back(Weight, Reg);
}
+ auto HeavyFirst = [](const auto &LHS, const auto &RHS) {
+ if (LHS.first != RHS.first)
+ return LHS.first > RHS.first;
+ return LHS.second.id() < RHS.second.id();
+ };
+ sort(FRegHints, HeavyFirst);
+ sort(VRegHints, HeavyFirst);
+ for (const auto &[Weight, Reg] : FRegHints) // Prefer physregs hints first.
+ MRI.addRegAllocationHint(LI.reg(), Reg);
+ for (const auto &[Weight, Reg] : VRegHints)
+ MRI.addRegAllocationHint(LI.reg(), Reg);
// Weakly boost the spill weight of hinted registers.
TotalWeight *= 1.01F;
>From d321b1229ec393ab8ee747b0e1922925db9f2e13 Mon Sep 17 00:00:00 2001
From: Valery Pykhtin <valery.pykhtin at gmail.com>
Date: Fri, 1 Nov 2024 10:43:12 +0100
Subject: [PATCH 2/2] Use one lists for all hints
---
llvm/lib/CodeGen/CalcSpillWeights.cpp | 31 ++++++++++++++++-----------
1 file changed, 19 insertions(+), 12 deletions(-)
diff --git a/llvm/lib/CodeGen/CalcSpillWeights.cpp b/llvm/lib/CodeGen/CalcSpillWeights.cpp
index baa4dec9075e1a..d1b22b60c0e88e 100644
--- a/llvm/lib/CodeGen/CalcSpillWeights.cpp
+++ b/llvm/lib/CodeGen/CalcSpillWeights.cpp
@@ -207,6 +207,21 @@ float VirtRegAuxInfo::weightCalcHelper(LiveInterval &LI, SlotIndex *Start,
NumInstr += 2;
}
+ // CopyHint is a sortable hint derived from a COPY instruction.
+ struct CopyHint {
+ Register Reg;
+ float Weight;
+ CopyHint(Register R, float W) : Reg(R), Weight(W) {}
+ bool operator<(const CopyHint &Rhs) const {
+ // Always prefer any physreg hint.
+ if (Reg.isPhysical() != Rhs.Reg.isPhysical())
+ return Reg.isPhysical();
+ if (Weight != Rhs.Weight)
+ return (Weight > Rhs.Weight);
+ return Reg.id() < Rhs.Reg.id(); // Tie-breaker.
+ }
+ };
+
bool IsExiting = false;
SmallDenseMap<Register, float, 8> Hint;
for (MachineRegisterInfo::reg_instr_nodbg_iterator
@@ -282,21 +297,13 @@ float VirtRegAuxInfo::weightCalcHelper(LiveInterval &LI, SlotIndex *Start,
// Don't add the target-type hint again.
Register SkipReg = TargetHint.first != 0 ? TargetHint.second : Register();
- SmallVector<std::pair<float, Register>, 4> FRegHints, VRegHints;
+ SmallVector<CopyHint, 8> RegHints;
for (const auto &[Reg, Weight] : Hint) {
if (Reg != SkipReg)
- (Reg.isPhysical() ? &FRegHints : &VRegHints)->emplace_back(Weight, Reg);
+ RegHints.emplace_back(Reg, Weight);
}
- auto HeavyFirst = [](const auto &LHS, const auto &RHS) {
- if (LHS.first != RHS.first)
- return LHS.first > RHS.first;
- return LHS.second.id() < RHS.second.id();
- };
- sort(FRegHints, HeavyFirst);
- sort(VRegHints, HeavyFirst);
- for (const auto &[Weight, Reg] : FRegHints) // Prefer physregs hints first.
- MRI.addRegAllocationHint(LI.reg(), Reg);
- for (const auto &[Weight, Reg] : VRegHints)
+ sort(RegHints);
+ for (const auto &[Reg, Weight] : RegHints)
MRI.addRegAllocationHint(LI.reg(), Reg);
// Weakly boost the spill weight of hinted registers.
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