[llvm] [DFAJumpThreading] Prevent pass from using too much memory. (PR #145482)
Bushev Dmitry via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 24 02:47:09 PDT 2025
https://github.com/dybv-sc updated https://github.com/llvm/llvm-project/pull/145482
>From e89a0860f4da654390014dd4b8d3beaf5808d5af Mon Sep 17 00:00:00 2001
From: Dmitry Bushev <dmitry.bushev at syntacore.com>
Date: Mon, 23 Jun 2025 08:54:56 +0000
Subject: [PATCH 1/2] [DFAJumpThreading] Prevent pass from using too much
memory.
The limit 'dfa-max-num-paths' that is used to control number of enumerated paths
was not checked against inside getPathsFromStateDefMap. It may lead to large memory consumption for
complex enough switch statements.
---
llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp b/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
index 938aab5879044..ac7af712bcf12 100644
--- a/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
@@ -618,6 +618,8 @@ struct AllSwitchPaths {
VisitedBlocks UniqueBlocks;
for (auto *IncomingBB : Phi->blocks()) {
+ if(Res.size() >= MaxNumPaths)
+ break;
if (!UniqueBlocks.insert(IncomingBB).second)
continue;
if (!SwitchOuterLoop->contains(IncomingBB))
@@ -657,6 +659,8 @@ struct AllSwitchPaths {
getPathsFromStateDefMap(StateDef, IncomingPhi, VB);
for (ThreadingPath &Path : PredPaths) {
Path.push_back(PhiBB);
+ if(Res.size() >= MaxNumPaths)
+ break;
Res.push_back(std::move(Path));
}
continue;
@@ -679,6 +683,10 @@ struct AllSwitchPaths {
ThreadingPath NewPath(Path);
NewPath.appendExcludingFirst(IPath);
NewPath.push_back(PhiBB);
+ if(Res.size() >= MaxNumPaths) {
+ VB.erase(PhiBB);
+ return Res;
+ }
Res.push_back(NewPath);
}
}
>From f0703ade890c6954f82b9a3dfbcbb6be4c38d650 Mon Sep 17 00:00:00 2001
From: Dmitry Bushev <dmitry.bushev at syntacore.com>
Date: Tue, 24 Jun 2025 09:46:39 +0000
Subject: [PATCH 2/2] Fix formatting
---
llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp b/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
index ac7af712bcf12..54cf3c523bdff 100644
--- a/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/DFAJumpThreading.cpp
@@ -618,7 +618,7 @@ struct AllSwitchPaths {
VisitedBlocks UniqueBlocks;
for (auto *IncomingBB : Phi->blocks()) {
- if(Res.size() >= MaxNumPaths)
+ if (Res.size() >= MaxNumPaths)
break;
if (!UniqueBlocks.insert(IncomingBB).second)
continue;
@@ -659,7 +659,7 @@ struct AllSwitchPaths {
getPathsFromStateDefMap(StateDef, IncomingPhi, VB);
for (ThreadingPath &Path : PredPaths) {
Path.push_back(PhiBB);
- if(Res.size() >= MaxNumPaths)
+ if (Res.size() >= MaxNumPaths)
break;
Res.push_back(std::move(Path));
}
@@ -683,10 +683,10 @@ struct AllSwitchPaths {
ThreadingPath NewPath(Path);
NewPath.appendExcludingFirst(IPath);
NewPath.push_back(PhiBB);
- if(Res.size() >= MaxNumPaths) {
+ if (Res.size() >= MaxNumPaths) {
VB.erase(PhiBB);
return Res;
- }
+ }
Res.push_back(NewPath);
}
}
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