[llvm-commits] [llvm] r44877 - /llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp

[Evan Cheng]

Hi Owen,

I know it's work in progress. But could you add some comments? I would  
like to follow the code. :-)

Thx,

Evan

On Dec 11, 2007, at 12:12 PM, Owen Anderson <resistor at mac.com> wrote:

> Author: resistor
> Date: Tue Dec 11 14:12:11 2007
> New Revision: 44877
>
> URL: http://llvm.org/viewvc/llvm-project?rev=44877&view=rev
> Log:
> More progress on StrongPHIElimination.  Now we actually USE the  
> DomForest!
>
> Modified:
>    llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp
>
> Modified: llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp?rev=44877&r1=44876&r2=44877&view=diff
>
> === 
> === 
> === 
> =====================================================================
> --- llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp (original)
> +++ llvm/trunk/lib/CodeGen/StrongPHIElimination.cpp Tue Dec 11  
> 14:12:11 2007
> @@ -97,6 +97,9 @@
>     void processBlock(MachineBasicBlock* MBB);
>
>     std::vector<DomForestNode*> computeDomForest(std::set<unsigned>&  
> instrs);
> +    void processPHIUnion(MachineInstr* Inst,
> +                         std::set<unsigned>& PHIUnion,
> +                          
> std::vector<StrongPHIElimination::DomForestNode*>& DF);
>     void breakCriticalEdges(MachineFunction &Fn);
>
>   };
> @@ -303,6 +306,92 @@
>   }
> }
>
> +void StrongPHIElimination::processPHIUnion(MachineInstr* Inst,
> +                                           std::set<unsigned>&  
> PHIUnion,
> +                         
> std::vector<StrongPHIElimination::DomForestNode*>& DF) {
> +
> +  std::vector<DomForestNode*> worklist(DF.begin(), DF.end());
> +  SmallPtrSet<DomForestNode*, 4> visited;
> +
> +  LiveVariables& LV = getAnalysis<LiveVariables>();
> +  unsigned DestReg = Inst->getOperand(0).getReg();
> +
> +  while (!worklist.empty()) {
> +    DomForestNode* DFNode = worklist.back();
> +
> +    LiveVariables::VarInfo& Info = LV.getVarInfo(DFNode->getReg());
> +    visited.insert(DFNode);
> +
> +    bool inserted = false;
> +    SmallPtrSet<DomForestNode*, 4> interferences;
> +    for (DomForestNode::iterator CI = DFNode->begin(), CE = DFNode- 
> >end();
> +         CI != CE; ++CI) {
> +      DomForestNode* child = *CI;
> +      LiveVariables::VarInfo& CInfo = LV.getVarInfo(child->getReg());
> +
> +      if (isLiveOut(Info, CInfo.DefInst->getParent())) {
> +        interferences.insert(child);
> +      } else if (isLiveIn(Info, CInfo.DefInst->getParent()) ||
> +                 Info.DefInst->getParent() == CInfo.DefInst- 
> >getParent()) {
> +        // FIXME: Add (p, c) to possible local interferences
> +      }
> +
> +      if (!visited.count(child)) {
> +        worklist.push_back(child);
> +        inserted = true;
> +      }
> +    }
> +
> +    if (interferences.size() == 1) {
> +      DomForestNode* child = *interferences.begin();
> +
> +      unsigned numParentCopies = 0;
> +      unsigned numChildCopies = 0;
> +      for (int i = Inst->getNumOperands() - 1; i >= 2; i-=2) {
> +        unsigned SrcReg = Inst->getOperand(i-1).getReg();
> +        if (SrcReg == DFNode->getReg()) numParentCopies++;
> +        else if (SrcReg == child->getReg()) numChildCopies++;
> +      }
> +
> +      if (numParentCopies < numChildCopies) {
> +        // Insert copies for child
> +        for (int i = Inst->getNumOperands() - 1; i >= 2; i-=2) {
> +          if (Inst->getOperand(i-1).getReg() == child->getReg()) {
> +            unsigned SrcReg = Inst->getOperand(i-1).getReg();
> +            MachineBasicBlock* From = Inst->getOperand(i).getMBB();
> +
> +            Waiting[From].push_back(std::make_pair(SrcReg, DestReg));
> +          }
> +        }
> +
> +        // FIXME: Make child's children parent's children
> +      } else {
> +        // Insert copies for parent
> +        for (int i = Inst->getNumOperands() - 1; i >= 2; i-=2) {
> +          if (Inst->getOperand(i-1).getReg() == DFNode->getReg()) {
> +            unsigned SrcReg = Inst->getOperand(i-1).getReg();
> +            MachineBasicBlock* From = Inst->getOperand(i).getMBB();
> +
> +            Waiting[From].push_back(std::make_pair(SrcReg, DestReg));
> +          }
> +        }
> +      }
> +    } else if (interferences.size() > 1) {
> +      // Insert copies for parent
> +      for (int i = Inst->getNumOperands() - 1; i >= 2; i-=2) {
> +        if (Inst->getOperand(i-1).getReg() == DFNode->getReg()) {
> +          unsigned SrcReg = Inst->getOperand(i-1).getReg();
> +          MachineBasicBlock* From = Inst->getOperand(i).getMBB();
> +
> +          Waiting[From].push_back(std::make_pair(SrcReg, DestReg));
> +        }
> +      }
> +    }
> +
> +    if (!inserted) worklist.pop_back();
> +  }
> +}
> +
> /// breakCriticalEdges - Break critical edges coming into blocks  
> with PHI
> /// nodes, preserving dominator and livevariable info.
> void StrongPHIElimination::breakCriticalEdges(MachineFunction &Fn) {
>
>
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