[llvm] [AMDGPU] Prevent cyclic behaviour in SIFoldOperands (PR #82099)
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llvm-commits at lists.llvm.org
Sat Feb 17 00:38:36 PST 2024
https://github.com/choikwa updated https://github.com/llvm/llvm-project/pull/82099
>From dff426cd86aa26c9d02c13ba368c46aa586fa7ff Mon Sep 17 00:00:00 2001
From: Kevin Choi <kevin.choi at amd.com>
Date: Sat, 17 Feb 2024 01:34:47 -0600
Subject: [PATCH] [AMDGPU] Prevent cyclic behaviour in SIFoldOperands
In SIFoldOperands::foldOperand, the recursion in REG_SEQUENCE handling
could result in infinite loop if UseMI and RSUseMI share a common
use operand, flipflopping between two instructions until stack overflows.
The fix is to prevent a cycle by using static seenMI set.
---
llvm/lib/Target/AMDGPU/SIFoldOperands.cpp | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp
index 8bf05682cbe7ea..8ad94ee1de910a 100644
--- a/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp
+++ b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp
@@ -15,6 +15,7 @@
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineOperand.h"
+#include <unordered_set>
#define DEBUG_TYPE "si-fold-operands"
using namespace llvm;
@@ -772,7 +773,7 @@ void SIFoldOperands::foldOperand(
if (UseMI->isRegSequence()) {
Register RegSeqDstReg = UseMI->getOperand(0).getReg();
unsigned RegSeqDstSubReg = UseMI->getOperand(UseOpIdx + 1).getImm();
-
+ static std::unordered_set<MachineInstr *> seenMI;
for (auto &RSUse : make_early_inc_range(MRI->use_nodbg_operands(RegSeqDstReg))) {
MachineInstr *RSUseMI = RSUse.getParent();
@@ -783,6 +784,10 @@ void SIFoldOperands::foldOperand(
if (RSUse.getSubReg() != RegSeqDstSubReg)
continue;
+ if (seenMI.count(RSUseMI) != 0)
+ continue;
+ seenMI.insert(RSUseMI);
+
foldOperand(OpToFold, RSUseMI, RSUseMI->getOperandNo(&RSUse), FoldList,
CopiesToReplace);
}
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