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[CodeGen] Introduce MachineBasicBlock::replacePhiUsesWith helper and use it. NFC

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Summary:
Found a couple of places in the code where all the PHI nodes
of a MBB is updated, replacing references to one MBB by
reference to another MBB instead.

This patch simply refactors the code to use a common helper
(MachineBasicBlock::replacePhiUsesWith) for such PHI node
updates.

Reviewers: t.p.northover, arsenm, uabelho

Subscribers: wdng, hiraditya, jsji, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66750

llvm-svn: 370463
This commit is contained in:
Bjorn Pettersson 2019-08-30 11:23:10 +00:00
parent 5f1dc5c211
commit 33fb4d996c
3 changed files with 20 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/llvm/CodeGen/MachineBasicBlock.h
View File

@ -735,6 +735,10 @@ public:
/// CFG so that it branches to 'New' instead.
void ReplaceUsesOfBlockWith(MachineBasicBlock *Old, MachineBasicBlock *New);
/// Update all phi nodes in this basic block to refer to basic block \p New
/// instead of basic block \p Old.
void replacePhiUsesWith(MachineBasicBlock *Old, MachineBasicBlock *New);
/// Various pieces of code can cause excess edges in the CFG to be inserted.
/// If we have proven that MBB can only branch to DestA and DestB, remove any
/// other MBB successors from the CFG. DestA and DestB can be null. Besides

30
lib/CodeGen/MachineBasicBlock.cpp
View File

@ -778,7 +778,8 @@ void MachineBasicBlock::transferSuccessors(MachineBasicBlock *FromMBB) {
while (!FromMBB->succ_empty()) {
MachineBasicBlock *Succ = *FromMBB->succ_begin();
// If probability list is empty it means we don't use it (disabled optimization).
// If probability list is empty it means we don't use it (disabled
// optimization).
if (!FromMBB->Probs.empty()) {
auto Prob = *FromMBB->Probs.begin();
addSuccessor(Succ, Prob);
@ -804,13 +805,7 @@ MachineBasicBlock::transferSuccessorsAndUpdatePHIs(MachineBasicBlock *FromMBB) {
FromMBB->removeSuccessor(Succ);
// Fix up any PHI nodes in the successor.
for (MachineBasicBlock::instr_iterator MI = Succ->instr_begin(),
ME = Succ->instr_end(); MI != ME && MI->isPHI(); ++MI)
for (unsigned i = 2, e = MI->getNumOperands()+1; i != e; i += 2) {
MachineOperand &MO = MI->getOperand(i);
if (MO.getMBB() == FromMBB)
MO.setMBB(this);
}
Succ->replacePhiUsesWith(FromMBB, this);
}
normalizeSuccProbs();
}
@ -985,13 +980,8 @@ MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ,
}
}
// Fix PHI nodes in Succ so they refer to NMBB instead of this
for (MachineBasicBlock::instr_iterator
i = Succ->instr_begin(),e = Succ->instr_end();
i != e && i->isPHI(); ++i)
for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
if (i->getOperand(ni+1).getMBB() == this)
i->getOperand(ni+1).setMBB(NMBB);
// Fix PHI nodes in Succ so they refer to NMBB instead of this.
Succ->replacePhiUsesWith(this, NMBB);
// Inherit live-ins from the successor
for (const auto &LI : Succ->liveins())
@ -1223,6 +1213,16 @@ void MachineBasicBlock::ReplaceUsesOfBlockWith(MachineBasicBlock *Old,
replaceSuccessor(Old, New);
}
void MachineBasicBlock::replacePhiUsesWith(MachineBasicBlock *Old,
MachineBasicBlock *New) {
for (MachineInstr &MI : phis())
for (unsigned i = 2, e = MI.getNumOperands() + 1; i != e; i += 2) {
MachineOperand &MO = MI.getOperand(i);
if (MO.getMBB() == Old)
MO.setMBB(New);
}
}
/// Various pieces of code can cause excess edges in the CFG to be inserted. If
/// we have proven that MBB can only branch to DestA and DestB, remove any other
/// MBB successors from the CFG. DestA and DestB can be null.

10
lib/CodeGen/MachinePipeliner.cpp
View File

@ -2234,15 +2234,7 @@ void SwingSchedulerDAG::generateEpilog(SMSchedule &Schedule, unsigned LastStage,
}
// Fix any Phi nodes in the loop exit block.
for (MachineInstr &MI : *LoopExitBB) {
if (!MI.isPHI())
break;
for (unsigned i = 2, e = MI.getNumOperands() + 1; i != e; i += 2) {
MachineOperand &MO = MI.getOperand(i);
if (MO.getMBB() == BB)
MO.setMBB(PredBB);
}
}
LoopExitBB->replacePhiUsesWith(BB, PredBB);
// Create a branch to the new epilog from the kernel.
// Remove the original branch and add a new branch to the epilog.