[llvm-commits] [llvm] r89213 - in /llvm/trunk/lib/CodeGen: PHIElimination.cpp PHIElimination.h

[Evan Cheng]

Thanks.

Evan
On Nov 18, 2009, at 10:01 AM, Jakob Stoklund Olesen wrote:

> Author: stoklund
> Date: Wed Nov 18 12:01:35 2009
> New Revision: 89213
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=89213&view=rev
> Log:
> Don't require LiveVariables for PHIElimination. Enable critical edge splitting
> 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.
> 
> Modified:
>    llvm/trunk/lib/CodeGen/PHIElimination.cpp
>    llvm/trunk/lib/CodeGen/PHIElimination.h
> 
> Modified: llvm/trunk/lib/CodeGen/PHIElimination.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PHIElimination.cpp?rev=89213&r1=89212&r2=89213&view=diff
> 
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/PHIElimination.cpp (original)
> +++ llvm/trunk/lib/CodeGen/PHIElimination.cpp Wed Nov 18 12:01:35 2009
> @@ -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 @@
> 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 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 @@
> }
> 
> 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) {
> 
> Modified: llvm/trunk/lib/CodeGen/PHIElimination.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PHIElimination.h?rev=89213&r1=89212&r2=89213&view=diff
> 
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/PHIElimination.h (original)
> +++ llvm/trunk/lib/CodeGen/PHIElimination.h Wed Nov 18 12:01:35 2009
> @@ -90,7 +90,8 @@
>     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
> 
> 
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