[llvm] [CodeGen] Use SmallMapVector for SpillPlacement::Node::Links (PR #194653)
Mingjie Xu via llvm-commits
llvm-commits at lists.llvm.org
Tue Apr 28 18:58:42 PDT 2026
https://github.com/Enna1 updated https://github.com/llvm/llvm-project/pull/194653
>From 540c40fc5ac9d0bd32d10f193fdc4afa94ec274c Mon Sep 17 00:00:00 2001
From: Enna1 <xumingjie.enna1 at bytedance.com>
Date: Tue, 28 Apr 2026 22:30:54 +0800
Subject: [PATCH 1/5] [CodeGen] Use SmallMapVector for
SpillPlacement::Node::Links
Previously, `SpillPlacement::Node::Links` was implemented as a `SmallVector`
of `(Weight, BundleNo)` pairs.
This patch replaces the `SmallVector` with a `SmallMapVector<unsigned, BlockFrequency, 4>`,
which stores `(BundleNo, Weight)` pairs. This allows for more efficient
lookups and weight accumulations when multiple links to the same bundle are
added.
---
llvm/lib/CodeGen/SpillPlacement.cpp | 30 ++++++++++++++---------------
1 file changed, 14 insertions(+), 16 deletions(-)
diff --git a/llvm/lib/CodeGen/SpillPlacement.cpp b/llvm/lib/CodeGen/SpillPlacement.cpp
index 55a96a22a00ec..4ac63cb2a6de2 100644
--- a/llvm/lib/CodeGen/SpillPlacement.cpp
+++ b/llvm/lib/CodeGen/SpillPlacement.cpp
@@ -81,11 +81,9 @@ struct SpillPlacement::Node {
/// variable should go in a register through this bundle.
int Value;
- using LinkVector = SmallVector<std::pair<BlockFrequency, unsigned>, 4>;
-
- /// Links - (Weight, BundleNo) for all transparent blocks connecting to other
+ /// Links - (BundleNo, Weight) for all transparent blocks connecting to other
/// bundles. The weights are all positive block frequencies.
- LinkVector Links;
+ SmallMapVector<unsigned, BlockFrequency, 4> Links;
/// SumLinkWeights - Cached sum of the weights of all links + ThresHold.
BlockFrequency SumLinkWeights;
@@ -120,13 +118,13 @@ struct SpillPlacement::Node {
SumLinkWeights += w;
// There can be multiple links to the same bundle, add them up.
- for (std::pair<BlockFrequency, unsigned> &L : Links)
- if (L.second == b) {
- L.first += w;
- return;
- }
+ auto It = Links.find(b);
+ if (It != Links.end()) {
+ It->second += w;
+ return;
+ }
// This must be the first link to b.
- Links.push_back(std::make_pair(w, b));
+ Links.insert(std::make_pair(b, w));
}
/// addBias - Bias this node.
@@ -152,11 +150,11 @@ struct SpillPlacement::Node {
// Compute the weighted sum of inputs.
BlockFrequency SumN = BiasN;
BlockFrequency SumP = BiasP;
- for (std::pair<BlockFrequency, unsigned> &L : Links) {
- if (nodes[L.second].Value == -1)
- SumN += L.first;
- else if (nodes[L.second].Value == 1)
- SumP += L.first;
+ for (std::pair<unsigned int, llvm::BlockFrequency> &L : Links) {
+ if (nodes[L.first].Value == -1)
+ SumN += L.second;
+ else if (nodes[L.first].Value == 1)
+ SumP += L.second;
}
// Each weighted sum is going to be less than the total frequency of the
@@ -180,7 +178,7 @@ struct SpillPlacement::Node {
void getDissentingNeighbors(SparseSet<unsigned> &List,
const Node nodes[]) const {
for (const auto &Elt : Links) {
- unsigned n = Elt.second;
+ unsigned n = Elt.first;
// Neighbors that already have the same value are not going to
// change because of this node changing.
if (Value != nodes[n].Value)
>From 9a9053865027459c0a7bd9f378d18f379b75e51e Mon Sep 17 00:00:00 2001
From: Enna1 <xumingjie.enna1 at bytedance.com>
Date: Tue, 28 Apr 2026 23:27:50 +0800
Subject: [PATCH 2/5] fixup! [CodeGen] Use SmallMapVector for
SpillPlacement::Node::Links
---
llvm/lib/CodeGen/SpillPlacement.cpp | 1 +
1 file changed, 1 insertion(+)
diff --git a/llvm/lib/CodeGen/SpillPlacement.cpp b/llvm/lib/CodeGen/SpillPlacement.cpp
index 4ac63cb2a6de2..620928a2a9a36 100644
--- a/llvm/lib/CodeGen/SpillPlacement.cpp
+++ b/llvm/lib/CodeGen/SpillPlacement.cpp
@@ -28,6 +28,7 @@
#include "llvm/CodeGen/SpillPlacement.h"
#include "llvm/ADT/BitVector.h"
+#include "llvm/ADT/MapVector.h"
#include "llvm/CodeGen/EdgeBundles.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
>From afd55e876b58d88ab033b3f212acc15e93f7a4ea Mon Sep 17 00:00:00 2001
From: Enna1 <xumingjie.enna1 at bytedance.com>
Date: Tue, 28 Apr 2026 23:39:28 +0800
Subject: [PATCH 3/5] address review comments
---
llvm/lib/CodeGen/SpillPlacement.cpp | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/CodeGen/SpillPlacement.cpp b/llvm/lib/CodeGen/SpillPlacement.cpp
index 620928a2a9a36..8884024df5954 100644
--- a/llvm/lib/CodeGen/SpillPlacement.cpp
+++ b/llvm/lib/CodeGen/SpillPlacement.cpp
@@ -119,13 +119,9 @@ struct SpillPlacement::Node {
SumLinkWeights += w;
// There can be multiple links to the same bundle, add them up.
- auto It = Links.find(b);
- if (It != Links.end()) {
+ auto [It, Inserted] = Links.try_emplace(b, w);
+ if (!Inserted)
It->second += w;
- return;
- }
- // This must be the first link to b.
- Links.insert(std::make_pair(b, w));
}
/// addBias - Bias this node.
>From 019c739fa96e5bafcaff9e0fa66e27539a9584df Mon Sep 17 00:00:00 2001
From: Enna1 <xumingjie.enna1 at bytedance.com>
Date: Wed, 29 Apr 2026 09:45:44 +0800
Subject: [PATCH 4/5] auto [BundleNo, Weight]
---
llvm/lib/CodeGen/SpillPlacement.cpp | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/llvm/lib/CodeGen/SpillPlacement.cpp b/llvm/lib/CodeGen/SpillPlacement.cpp
index 8884024df5954..837ebbf62c5e8 100644
--- a/llvm/lib/CodeGen/SpillPlacement.cpp
+++ b/llvm/lib/CodeGen/SpillPlacement.cpp
@@ -147,11 +147,11 @@ struct SpillPlacement::Node {
// Compute the weighted sum of inputs.
BlockFrequency SumN = BiasN;
BlockFrequency SumP = BiasP;
- for (std::pair<unsigned int, llvm::BlockFrequency> &L : Links) {
- if (nodes[L.first].Value == -1)
- SumN += L.second;
- else if (nodes[L.first].Value == 1)
- SumP += L.second;
+ for (auto [BundleNo, Weight] : Links) {
+ if (nodes[BundleNo].Value == -1)
+ SumN += Weight;
+ else if (nodes[BundleNo].Value == 1)
+ SumP += Weight;
}
// Each weighted sum is going to be less than the total frequency of the
>From da472384665ad643ccf6d9da44bdda037c27ac18 Mon Sep 17 00:00:00 2001
From: Enna1 <xumingjie.enna1 at bytedance.com>
Date: Wed, 29 Apr 2026 09:57:48 +0800
Subject: [PATCH 5/5] getDissentingNeighbors
---
llvm/lib/CodeGen/SpillPlacement.cpp | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/llvm/lib/CodeGen/SpillPlacement.cpp b/llvm/lib/CodeGen/SpillPlacement.cpp
index 837ebbf62c5e8..1b3cd9ccbf08b 100644
--- a/llvm/lib/CodeGen/SpillPlacement.cpp
+++ b/llvm/lib/CodeGen/SpillPlacement.cpp
@@ -174,12 +174,11 @@ struct SpillPlacement::Node {
void getDissentingNeighbors(SparseSet<unsigned> &List,
const Node nodes[]) const {
- for (const auto &Elt : Links) {
- unsigned n = Elt.first;
+ for (auto [BundleNo, _] : Links) {
// Neighbors that already have the same value are not going to
// change because of this node changing.
- if (Value != nodes[n].Value)
- List.insert(n);
+ if (Value != nodes[BundleNo].Value)
+ List.insert(BundleNo);
}
}
};
More information about the llvm-commits
mailing list