[llvm] [CodeGen] Extract copy-paste on PHI MachineInstr income removal. (PR #158634)
Afanasyev Ivan via llvm-commits
llvm-commits at lists.llvm.org
Thu Sep 18 15:45:56 PDT 2025
https://github.com/ivafanas updated https://github.com/llvm/llvm-project/pull/158634
>From e1a30e73e810bb9e4aee5a61ee3b3bb350ab026f Mon Sep 17 00:00:00 2001
From: Ivan Afanasyev <ivafanas at gmail.com>
Date: Thu, 18 Sep 2025 22:36:19 +0700
Subject: [PATCH] [CodeGen] Extract copy-paste on PHI MachineInstr income
removal.
---
llvm/include/llvm/CodeGen/MachineBasicBlock.h | 9 +++++++++
llvm/include/llvm/CodeGen/MachineInstr.h | 10 ++++++++++
llvm/lib/CodeGen/MachineBasicBlock.cpp | 10 ++++++++++
llvm/lib/CodeGen/MachineInstr.cpp | 20 +++++++++++++++++++
llvm/lib/CodeGen/ModuloSchedule.cpp | 19 +++---------------
llvm/lib/CodeGen/TailDuplicator.cpp | 8 +-------
llvm/lib/CodeGen/UnreachableBlockElim.cpp | 14 ++-----------
7 files changed, 55 insertions(+), 35 deletions(-)
diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
index 94139b64a3e30..25be58081cfd0 100644
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -1503,6 +1503,15 @@ inline auto instructionsWithoutDebug(IterT It, IterT End,
});
}
+/// Iterate over block PHI instructions and remove all incoming values for
+/// PredMBB.
+///
+/// Function does not erase PHI instructions even if they have single income or
+/// do not have incoming values ar all. It is a caller responsibility to make
+/// decision how to process PHI instructions after incoming values removal.
+void removePHIsIncomingValuesForMBB(MachineBasicBlock &MBB,
+ const MachineBasicBlock &PredMBB);
+
} // end namespace llvm
#endif // LLVM_CODEGEN_MACHINEBASICBLOCK_H
diff --git a/llvm/include/llvm/CodeGen/MachineInstr.h b/llvm/include/llvm/CodeGen/MachineInstr.h
index 10a9b1ff1411d..297131eefbf66 100644
--- a/llvm/include/llvm/CodeGen/MachineInstr.h
+++ b/llvm/include/llvm/CodeGen/MachineInstr.h
@@ -2115,6 +2115,16 @@ inline raw_ostream& operator<<(raw_ostream &OS, const MachineInstr &MI) {
return OS;
}
+/// Remove all incoming values of Phi instruction for the given block.
+///
+/// Return deleted operands count.
+///
+/// Function does not erase PHI instruction even if it has single income or does
+/// not have incoming values at all. It is a caller responsibility to make
+/// decision how to process PHI instruction after incoming values removed.
+unsigned removePHIIncomingValueForMBB(MachineInstr &Phi,
+ const MachineBasicBlock &MBB);
+
} // end namespace llvm
#endif // LLVM_CODEGEN_MACHINEINSTR_H
diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 08a51b9b0242a..7c8ac9c5153d4 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -1805,3 +1805,13 @@ bool MachineBasicBlock::sizeWithoutDebugLargerThan(unsigned Limit) const {
const MBBSectionID MBBSectionID::ColdSectionID(MBBSectionID::SectionType::Cold);
const MBBSectionID
MBBSectionID::ExceptionSectionID(MBBSectionID::SectionType::Exception);
+
+namespace llvm {
+
+void removePHIsIncomingValuesForMBB(MachineBasicBlock &MBB,
+ const MachineBasicBlock &PredMBB) {
+ for (MachineInstr &Phi : MBB.phis())
+ removePHIIncomingValueForMBB(Phi, PredMBB);
+}
+
+} // end namespace llvm
diff --git a/llvm/lib/CodeGen/MachineInstr.cpp b/llvm/lib/CodeGen/MachineInstr.cpp
index 2c06c5ad4a5e4..1dd76c1bbf808 100644
--- a/llvm/lib/CodeGen/MachineInstr.cpp
+++ b/llvm/lib/CodeGen/MachineInstr.cpp
@@ -2747,3 +2747,23 @@ bool MachineInstr::mayFoldInlineAsmRegOp(unsigned OpId) const {
return F.getRegMayBeFolded();
return false;
}
+
+namespace llvm {
+
+unsigned removePHIIncomingValueForMBB(MachineInstr &Phi,
+ const MachineBasicBlock &MBB) {
+ assert(Phi.isPHI());
+
+ // Phi might have multiple entries for MBB. Need to remove them all.
+ unsigned RemovedCount = 0;
+ for (unsigned N = Phi.getNumOperands(); N > 2; N -= 2) {
+ if (Phi.getOperand(N - 1).getMBB() == &MBB) {
+ Phi.removeOperand(N - 1);
+ Phi.removeOperand(N - 2);
+ RemovedCount += 2;
+ }
+ }
+ return RemovedCount;
+}
+
+} // end namespace llvm
diff --git a/llvm/lib/CodeGen/ModuloSchedule.cpp b/llvm/lib/CodeGen/ModuloSchedule.cpp
index 21bf052d1fdaf..bc768cdbea73a 100644
--- a/llvm/lib/CodeGen/ModuloSchedule.cpp
+++ b/llvm/lib/CodeGen/ModuloSchedule.cpp
@@ -10,6 +10,7 @@
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/CodeGen/LiveIntervals.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
@@ -859,20 +860,6 @@ void ModuloScheduleExpander::splitLifetimes(MachineBasicBlock *KernelBB,
}
}
-/// Remove the incoming block from the Phis in a basic block.
-static void removePhis(MachineBasicBlock *BB, MachineBasicBlock *Incoming) {
- for (MachineInstr &MI : *BB) {
- if (!MI.isPHI())
- break;
- for (unsigned i = 1, e = MI.getNumOperands(); i != e; i += 2)
- if (MI.getOperand(i + 1).getMBB() == Incoming) {
- MI.removeOperand(i + 1);
- MI.removeOperand(i);
- break;
- }
- }
-}
-
/// Create branches from each prolog basic block to the appropriate epilog
/// block. These edges are needed if the loop ends before reaching the
/// kernel.
@@ -906,7 +893,7 @@ void ModuloScheduleExpander::addBranches(MachineBasicBlock &PreheaderBB,
Prolog->removeSuccessor(LastPro);
LastEpi->removeSuccessor(Epilog);
numAdded = TII->insertBranch(*Prolog, Epilog, nullptr, Cond, DebugLoc());
- removePhis(Epilog, LastEpi);
+ removePHIsIncomingValuesForMBB(*Epilog, *LastEpi);
// Remove the blocks that are no longer referenced.
if (LastPro != LastEpi) {
for (auto &MI : *LastEpi)
@@ -924,7 +911,7 @@ void ModuloScheduleExpander::addBranches(MachineBasicBlock &PreheaderBB,
LastPro->eraseFromParent();
} else {
numAdded = TII->insertBranch(*Prolog, LastPro, nullptr, Cond, DebugLoc());
- removePhis(Epilog, Prolog);
+ removePHIsIncomingValuesForMBB(*Epilog, *Prolog);
}
LastPro = Prolog;
LastEpi = Epilog;
diff --git a/llvm/lib/CodeGen/TailDuplicator.cpp b/llvm/lib/CodeGen/TailDuplicator.cpp
index 9b1420a94142d..df91a08c9d4eb 100644
--- a/llvm/lib/CodeGen/TailDuplicator.cpp
+++ b/llvm/lib/CodeGen/TailDuplicator.cpp
@@ -375,13 +375,7 @@ void TailDuplicator::processPHI(
if (!Remove)
return;
- // MI might have multiple entries for PredBB. Need to remove them all.
- for (unsigned N = MI->getNumOperands(); N > 2; N -= 2) {
- if (MI->getOperand(N - 1).getMBB() == PredBB) {
- MI->removeOperand(N - 1);
- MI->removeOperand(N - 2);
- }
- }
+ removePHIIncomingValueForMBB(*MI, *PredBB);
if (MI->getNumOperands() == 1 && !TailBB->hasAddressTaken())
MI->eraseFromParent();
diff --git a/llvm/lib/CodeGen/UnreachableBlockElim.cpp b/llvm/lib/CodeGen/UnreachableBlockElim.cpp
index 512e83db40a5a..e5756d9a31ad3 100644
--- a/llvm/lib/CodeGen/UnreachableBlockElim.cpp
+++ b/llvm/lib/CodeGen/UnreachableBlockElim.cpp
@@ -22,6 +22,7 @@
#include "llvm/CodeGen/UnreachableBlockElim.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
@@ -155,18 +156,7 @@ bool UnreachableMachineBlockElim::run(MachineFunction &F) {
if (MDT && MDT->getNode(&BB)) MDT->eraseNode(&BB);
while (!BB.succ_empty()) {
- MachineBasicBlock* succ = *BB.succ_begin();
-
- for (MachineInstr &Phi : succ->phis()) {
- for (unsigned i = Phi.getNumOperands() - 1; i >= 2; i -= 2) {
- if (Phi.getOperand(i).isMBB() &&
- Phi.getOperand(i).getMBB() == &BB) {
- Phi.removeOperand(i);
- Phi.removeOperand(i - 1);
- }
- }
- }
-
+ removePHIsIncomingValuesForMBB(**BB.succ_begin(), BB);
BB.removeSuccessor(BB.succ_begin());
}
}
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