[Beignet] [PATCH 02/18] GBE: Remove BBs if it only has a label instruction.

[Gong, Zhigang]

> -----Original Message-----
> From: Yang, Rong R
> Sent: Wednesday, April 2, 2014 4:54 PM
> To: Gong, Zhigang; beignet at lists.freedesktop.org
> Subject: RE: [Beignet] [PATCH 02/18] GBE: Remove BBs if it only has a label
> instruction.
> 
> 
> 
> -----Original Message-----
> From: Gong, Zhigang
> Sent: Wednesday, April 02, 2014 4:52 PM
> To: Yang, Rong R; beignet at lists.freedesktop.org
> Subject: RE: [Beignet] [PATCH 02/18] GBE: Remove BBs if it only has a label
> instruction.
> 
> 
> 
> > -----Original Message-----
> > From: Yang, Rong R
> > Sent: Wednesday, April 2, 2014 4:30 PM
> > To: Gong, Zhigang; beignet at lists.freedesktop.org
> > Cc: Gong, Zhigang
> > Subject: RE: [Beignet] [PATCH 02/18] GBE: Remove BBs if it only has a
> > label instruction.
> >
> > One comment.
> >
> > -----Original Message-----
> > From: Beignet [mailto:beignet-bounces at lists.freedesktop.org] On Behalf
> > Of Zhigang Gong
> > Sent: Friday, March 28, 2014 3:11 PM
> > To: beignet at lists.freedesktop.org
> > Cc: Gong, Zhigang
> > Subject: [Beignet] [PATCH 02/18] GBE: Remove BBs if it only has a
> > label instruction.
> >
> > Signed-off-by: Zhigang Gong <zhigang.gong at intel.com>
> > ---
> >  backend/src/ir/context.cpp  |  3 +-
> >  backend/src/ir/function.cpp | 75
> > +++++++++++++++++++++++++++++++++++++++++++++
> >  backend/src/ir/function.hpp |  4 +++
> >  3 files changed, 81 insertions(+), 1 deletion(-)
> >
> > diff --git a/backend/src/ir/context.cpp b/backend/src/ir/context.cpp
> > index
> > 15d3b0a..0fd6803 100644
> > --- a/backend/src/ir/context.cpp
> > +++ b/backend/src/ir/context.cpp
> > @@ -75,7 +75,8 @@ namespace ir {
> >      // Remove all returns and insert one unique return block at the end of
> the
> >      // function
> >      lowerReturn(unit, fn->getName());
> > -
> > +    // Remove empty labels at first
> > +    fn->removeEmptyLabels();
> >      // Properly order labels and compute the CFG, it's needed by
> > FunctionArgumentLower
> >      fn->sortLabels();
> >      fn->computeCFG();
> > diff --git a/backend/src/ir/function.cpp b/backend/src/ir/function.cpp
> > index a6aecb5..7ea3b1a 100644
> > --- a/backend/src/ir/function.cpp
> > +++ b/backend/src/ir/function.cpp
> > @@ -64,6 +64,81 @@ namespace ir {
> >      loops.push_back(GBE_NEW(Loop, bbs, exits));
> >    }
> >
> > +  void Function::removeBlock(BasicBlock *BB) {
> > +    GBE_ASSERTM(BB->begin() == BB->end(), "BB to be removed is not
> > empty");
> > +    if (BB->getPrevBlock() != NULL && BB->getNextBlock() != NULL) {
> > +      BB->getPrevBlock()->nextBlock = BB->getNextBlock();
> > +      BB->getNextBlock()->prevBlock = BB->getPrevBlock();
> > +    }
> >
> > >>>>>>>>How about BB->getPrevBlock() == NULL || BB->getNextBlock() ==
> > NULL case?
> 
> For those cases, the BB is not in any CFG, there is nothing we need to do for it.
> 
> >>>> What's the getPrevBlock of the first BB and getNextBlock of the last BB.

I got your point now. Actually, the first(initialize) and last BB(ret) will never be an empty block.


> 
> >
> >
> >
> > +    for(auto it = blocks.begin(); it != blocks.end(); it++) {
> > +      if (*it == BB) {
> > +        blocks.erase(it);
> > +        break;
> > +      }
> > +    }
> > +  }
> > +
> > +  void Function::removeEmptyLabels(void) {
> > +    // Empty label map, we map the removed label to the next label.
> > +    map<LabelIndex, LabelIndex> labelMap;
> > +    map<LabelIndex, LabelIndex> revLabelMap;
> > +    foreachBlock([&](BasicBlock &BB) {
> > +      Instruction * insn = BB.getLastInstruction();
> > +      if (insn->getOpcode() == OP_LABEL) {
> > +        const LabelIndex index = BB.getLabelIndex();
> > +        const LabelIndex next = LabelIndex(((uint16_t)index) + 1);
> > +        labelMap.insert(std::make_pair(index, next));
> > +        auto needFixIt = revLabelMap.find(index);
> > +        if (needFixIt != revLabelMap.end()) {
> > +          // Fix up the previous map with the new next label.
> > +          labelMap.erase(needFixIt->second);
> > +          labelMap.insert(std::make_pair(needFixIt->second, next));
> > +        }
> > +        revLabelMap.insert(std::make_pair(next, index));
> > +        insn->remove();
> > +        removeBlock(&BB);
> > +      }
> > +    });
> > +
> > +    // fix labels for loops
> > +    for (auto &x : loops) {
> > +      for (auto &y : x->bbs) {
> > +        if (labelMap.find(y) != labelMap.end())
> > +          y = labelMap.find(y)->second;
> > +      }
> > +
> > +      for (auto &z : x->exits) {
> > +        if (labelMap.find(z.first) != labelMap.end())
> > +          z.first = labelMap.find(z.first)->second;
> > +        if (labelMap.find(z.second) != labelMap.end())
> > +          z.second = labelMap.find(z.second)->second;
> > +      }
> > +    }
> > +
> > +
> > +    // Patch all branch instructions with the new labels
> > +    foreachInstruction([&](Instruction &insn) {
> > +      if (insn.getOpcode() != OP_BRA)
> > +        return;
> > +
> > +      // Get the current branch instruction
> > +      BranchInstruction &bra = cast<BranchInstruction>(insn);
> > +      const LabelIndex index = bra.getLabelIndex();
> > +      if (labelMap.find(index) == labelMap.end())
> > +        return;
> > +      const LabelIndex newIndex = labelMap.find(index)->second;
> > +
> > +      // Insert the patched branch instruction
> > +      if (bra.isPredicated() == true) {
> > +        const Instruction newBra = BRA(newIndex,
> > bra.getPredicateIndex());
> > +        newBra.replace(&insn);
> > +      } else {
> > +        const Instruction newBra = BRA(newIndex);
> > +        newBra.replace(&insn);
> > +      }
> > +    });
> > +  }
> > +
> >    void Function::sortLabels(void) {
> >      uint32_t last = 0;
> >
> > diff --git a/backend/src/ir/function.hpp b/backend/src/ir/function.hpp
> > index 03aeaeb..ad4773e 100644
> > --- a/backend/src/ir/function.hpp
> > +++ b/backend/src/ir/function.hpp
> > @@ -281,6 +281,10 @@ namespace ir {
> >      void computeCFG(void);
> >      /*! Sort labels in increasing orders (top block has the smallest label) */
> >      void sortLabels(void);
> > +    /*! Remove empty block. */
> > +    void removeBlock(BasicBlock *BB);
> > +    /*! Remove empty Label. */
> > +    void removeEmptyLabels(void);
> >      /*! Get the pointer family */
> >      RegisterFamily getPointerFamily(void) const;
> >      /*! Number of registers in the register file */
> > --
> > 1.8.3.2
> >
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