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Don't require LiveVariables for PHIElimination. Enable critical edge splitting

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when LiveVariables is available.

The -split-phi-edges is now gone, and so is the hack to disable it when using
the local register allocator. The PHIElimination pass no longer has
LiveVariables as a prerequisite - that is what broke the local allocator.
Instead we do critical edge splitting when possible - that is when
LiveVariables is available.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89213 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2009-11-18 18:01:35 +00:00
parent e1caa98c5b
commit 0257dd375d
2 changed files with 9 additions and 28 deletions
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34
lib/CodeGen/PHIElimination.cpp
View File

@ -21,7 +21,6 @@
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegAllocRegistry.h"
#include "llvm/Function.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/ADT/SmallPtrSet.h"
@ -37,37 +36,17 @@ using namespace llvm;
STATISTIC(NumAtomic, "Number of atomic phis lowered");
STATISTIC(NumSplits, "Number of critical edges split on demand");
static cl::opt<bool>
SplitEdges("split-phi-edges",
cl::desc("Split critical edges during phi elimination"),
cl::init(false), cl::Hidden);
char PHIElimination::ID = 0;
static RegisterPass<PHIElimination>
X("phi-node-elimination", "Eliminate PHI nodes for register allocation");
const PassInfo *const llvm::PHIEliminationID = &X;
namespace llvm { FunctionPass *createLocalRegisterAllocator(); }
// Should we run edge splitting?
static bool shouldSplitEdges() {
// Edge splitting breaks the local register allocator. It cannot tolerate
// LiveVariables being run.
if (RegisterRegAlloc::getDefault() == createLocalRegisterAllocator)
return false;
return SplitEdges;
}
void llvm::PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreserved<LiveVariables>();
AU.addPreserved<MachineDominatorTree>();
if (shouldSplitEdges()) {
AU.addRequired<LiveVariables>();
} else {
AU.setPreservesCFG();
AU.addPreservedID(MachineLoopInfoID);
}
// rdar://7401784 This would be nice:
// AU.addPreservedID(MachineLoopInfoID);
MachineFunctionPass::getAnalysisUsage(AU);
}
@ -79,9 +58,9 @@ bool llvm::PHIElimination::runOnMachineFunction(MachineFunction &Fn) {
bool Changed = false;
// Split critical edges to help the coalescer
if (shouldSplitEdges())
if (LiveVariables *LV = getAnalysisIfAvailable<LiveVariables>())
for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)
Changed |= SplitPHIEdges(Fn, *I);
Changed |= SplitPHIEdges(Fn, *I, *LV);
// Populate VRegPHIUseCount
analyzePHINodes(Fn);
@ -361,10 +340,11 @@ void llvm::PHIElimination::analyzePHINodes(const MachineFunction& Fn) {
}
bool llvm::PHIElimination::SplitPHIEdges(MachineFunction &MF,
MachineBasicBlock &MBB) {
MachineBasicBlock &MBB,
LiveVariables &LV) {
if (MBB.empty() || MBB.front().getOpcode() != TargetInstrInfo::PHI)
return false; // Quick exit for basic blocks without PHIs.
LiveVariables &LV = getAnalysis<LiveVariables>();
for (MachineBasicBlock::const_iterator BBI = MBB.begin(), BBE = MBB.end();
BBI != BBE && BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI) {
for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2) {

3
lib/CodeGen/PHIElimination.h
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@ -90,7 +90,8 @@ namespace llvm {
void analyzePHINodes(const MachineFunction& Fn);
/// Split critical edges where necessary for good coalescer performance.
bool SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB);
bool SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB,
LiveVariables &LV);
/// isLiveOut - Determine if Reg is live out from MBB, when not
/// considering PHI nodes. This means that Reg is either killed by