From: Nate Begeman Date: Tue, 10 Aug 2010 21:38:12 +0000 (+0000) Subject: Add the minimal amount of smarts necessary to instcombine of shufflevectors to recognize X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=95743d8748a85bbb03aff3b3baae728c138acbab;p=oota-llvm.git Add the minimal amount of smarts necessary to instcombine of shufflevectors to recognize patterns generated by clang for transpose of a matrix in generic vectors. This is made of two parts: 1) Propagating vector extracts of hi/lo half into their users 2) Recognizing an insertion of even elements followed by the odd elements as an unpack. Testcase to come, but this shrinks the # of shuffle instructions generated on x86 from ~40 to the minimal 8. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110734 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp index a58124d7032..8c987b67b7f 100644 --- a/lib/Transforms/InstCombine/InstCombineVectorOps.cpp +++ b/lib/Transforms/InstCombine/InstCombineVectorOps.cpp @@ -448,10 +448,8 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { if (isa(SVI.getOperand(2))) return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType())); - unsigned VWidth = cast(SVI.getType())->getNumElements(); - - if (VWidth != cast(LHS->getType())->getNumElements()) - return 0; + unsigned VWidth = Mask.size(); + unsigned LHSWidth = cast(LHS->getType())->getNumElements(); APInt UndefElts(VWidth, 0); APInt AllOnesEltMask(APInt::getAllOnesValue(VWidth)); @@ -464,14 +462,12 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { // Canonicalize shuffle(x ,x,mask) -> shuffle(x, undef,mask') // Canonicalize shuffle(undef,x,mask) -> shuffle(x, undef,mask'). if (LHS == RHS || isa(LHS)) { - if (isa(LHS) && LHS == RHS) { - // shuffle(undef,undef,mask) -> undef. - return ReplaceInstUsesWith(SVI, LHS); - } + if (isa(LHS) && LHS == RHS) + return ReplaceInstUsesWith(SVI, UndefValue::get(SVI.getType())); // Remap any references to RHS to use LHS. std::vector Elts; - for (unsigned i = 0, e = Mask.size(); i != e; ++i) { + for (unsigned i = 0, e = LHSWidth; i != VWidth; ++i) { if (Mask[i] >= 2*e) Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); else { @@ -495,67 +491,148 @@ Instruction *InstCombiner::visitShuffleVectorInst(ShuffleVectorInst &SVI) { } // Analyze the shuffle, are the LHS or RHS and identity shuffles? - bool isLHSID = true, isRHSID = true; - - for (unsigned i = 0, e = Mask.size(); i != e; ++i) { - if (Mask[i] >= e*2) continue; // Ignore undef values. - // Is this an identity shuffle of the LHS value? - isLHSID &= (Mask[i] == i); + if (VWidth == LHSWidth) { + bool isLHSID = true, isRHSID = true; - // Is this an identity shuffle of the RHS value? - isRHSID &= (Mask[i]-e == i); + for (unsigned i = 0, e = Mask.size(); i != e; ++i) { + if (Mask[i] >= e*2) continue; // Ignore undef values. + // Is this an identity shuffle of the LHS value? + isLHSID &= (Mask[i] == i); + + // Is this an identity shuffle of the RHS value? + isRHSID &= (Mask[i]-e == i); + } + + // Eliminate identity shuffles. + if (isLHSID) return ReplaceInstUsesWith(SVI, LHS); + if (isRHSID) return ReplaceInstUsesWith(SVI, RHS); } - // Eliminate identity shuffles. - if (isLHSID) return ReplaceInstUsesWith(SVI, LHS); - if (isRHSID) return ReplaceInstUsesWith(SVI, RHS); - - // If the LHS is a shufflevector itself, see if we can combine it with this - // one without producing an unusual shuffle. Here we are really conservative: - // we are absolutely afraid of producing a shuffle mask not in the input - // program, because the code gen may not be smart enough to turn a merged - // shuffle into two specific shuffles: it may produce worse code. As such, - // we only merge two shuffles if the result is one of the two input shuffle - // masks. In this case, merging the shuffles just removes one instruction, - // which we know is safe. This is good for things like turning: - // (splat(splat)) -> splat. - if (ShuffleVectorInst *LHSSVI = dyn_cast(LHS)) { - if (isa(RHS)) { - std::vector LHSMask = getShuffleMask(LHSSVI); - - if (LHSMask.size() == Mask.size()) { - std::vector NewMask; - for (unsigned i = 0, e = Mask.size(); i != e; ++i) - if (Mask[i] >= e) - NewMask.push_back(2*e); - else - NewMask.push_back(LHSMask[Mask[i]]); - - // If the result mask is equal to the src shuffle or this - // shuffle mask, do the replacement. - if (NewMask == LHSMask || NewMask == Mask) { - unsigned LHSInNElts = - cast(LHSSVI->getOperand(0)->getType())-> - getNumElements(); - std::vector Elts; - for (unsigned i = 0, e = NewMask.size(); i != e; ++i) { - if (NewMask[i] >= LHSInNElts*2) { - Elts.push_back(UndefValue::get( - Type::getInt32Ty(SVI.getContext()))); - } else { - Elts.push_back(ConstantInt::get( - Type::getInt32Ty(SVI.getContext()), - NewMask[i])); - } - } - return new ShuffleVectorInst(LHSSVI->getOperand(0), - LHSSVI->getOperand(1), - ConstantVector::get(Elts)); - } + // Check for a handful of important shuffle(shuffle()) combinations. + ShuffleVectorInst *LSVI = dyn_cast(LHS); + if (!LSVI) + return MadeChange ? &SVI : 0; + + LHS = LSVI->getOperand(0); + std::vector LHSMask = getShuffleMask(LSVI); + unsigned LHSInNElts = cast(LHS->getType())->getNumElements(); + + // If lhs is identity, propagate + bool isLHSLoExtract = true, isLHSHiExtract = true; + for (unsigned i = 0, e = LHSMask.size(); i != e; ++i) { + if (LHSMask[i] >= LHSInNElts*2) continue; // Ignore undef values; + isLHSLoExtract &= (LHSMask[i] == i); + isLHSHiExtract &= (LHSMask[i] == i+(LHSInNElts/2)); + } + if ((isLHSLoExtract || isLHSHiExtract) && + (isa(RHS) || (LHSWidth == LHSInNElts))) { + std::vector Elts; + for (unsigned i = 0, e = VWidth; i != e; ++i) { + if (Mask[i] >= 2*LHSWidth) + Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); + else + Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()), + LHSMask[Mask[i]])); + } + if (isa(RHS)) + RHS = UndefValue::get(LHS->getType()); + return new ShuffleVectorInst(LHS, RHS, ConstantVector::get(Elts)); + } + + // If svi + lhs forms a full unpack, merge it. This allows llvm to emit + // efficient code for matrix transposes written with generic vector ops. + if ((LHSMask.size() == Mask.size()) && isPowerOf2_32(Mask.size()) && + (Mask.size() > 1)) { + bool isUnpackLo = true, isUnpackHi = true; + // check lhs mask for <0, u, 1, u .. >; + for (unsigned i = 0, e = LHSMask.size(); i != e; ++i) { + if (LHSMask[i] >= 2*e) continue; + isUnpackLo &= (LHSMask[i] == (i/2)); + isUnpackHi &= (LHSMask[i] == (i/2) + (e/2)); + } + for (unsigned i = 0, e = Mask.size(); i != e && (isUnpackLo || isUnpackHi); + i += 2) { + isUnpackLo &= (Mask[i] == i) && (Mask[i+1] == (i/2)+e); + isUnpackHi &= (Mask[i] == i) && (Mask[i+1] == (i/2)+e+(e/2)); + } + if (isUnpackLo || isUnpackHi) { + std::vector Elts; + for (unsigned i = 0, e = Mask.size(); i != e; ++i) { + if (Mask[i] >= 2*e) + Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); + else if (Mask[i] >= e) + Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()), + Mask[i])); + else + Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()), + LHSMask[Mask[i]])); } + return new ShuffleVectorInst(LHS, RHS, ConstantVector::get(Elts)); + } + } + + // If rhs is shuffle + identity, propagate. + if (ShuffleVectorInst *RSVI = dyn_cast(RHS)) { + std::vector RHSMask = getShuffleMask(RSVI); + unsigned RHSInNElts = + cast(RSVI->getOperand(0)->getType())->getNumElements(); + + // If rhs is identity, propagate + bool isRHSLoExtract = true, isRHSHiExtract = true; + for (unsigned i = 0, e = RHSMask.size(); i != e; ++i) { + if (RHSMask[i] >= RHSInNElts*2) continue; // Ignore undef values; + isRHSLoExtract &= (RHSMask[i] == i); + isRHSHiExtract &= (RHSMask[i] == i+(RHSInNElts/2)); + } + if ((isRHSLoExtract || isRHSHiExtract) && (LHSWidth == RHSInNElts)) { + std::vector Elts; + for (unsigned i = 0, e = VWidth; i != e; ++i) { + if (Mask[i] >= 2*LHSWidth) + Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); + else if (Mask[i] < LHSWidth) + Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()), + Mask[i])); + else + Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()), + RHSMask[Mask[i]-LHSWidth]+LHSWidth)); + } + SVI.setOperand(1, RSVI->getOperand(0)); + SVI.setOperand(2, ConstantVector::get(Elts)); + return &SVI; } } + // Be extremely conservative when merging shufflevector instructions. It is + // difficult for the code generator to recognize a merged shuffle, which + // usually leads to worse code from merging a shuffle. + if (!isa(RHS)) + return MadeChange ? &SVI : 0; + + // If the merged shuffle mask is one of the two input shuffle masks, which + // just removes one instruction. This should handle splat(splat) -> splat. + if (LHSMask.size() == Mask.size()) { + std::vector NewMask; + for (unsigned i = 0, e = Mask.size(); i != e; ++i) + if (Mask[i] >= e) + NewMask.push_back(2*e); + else + NewMask.push_back(LHSMask[Mask[i]]); + + // If the result mask is equal to the src shuffle or this shuffle mask, + // do the replacement. + if (NewMask == LHSMask || NewMask == Mask) { + std::vector Elts; + for (unsigned i = 0, e = NewMask.size(); i != e; ++i) { + if (NewMask[i] >= LHSInNElts*2) { + Elts.push_back(UndefValue::get(Type::getInt32Ty(SVI.getContext()))); + } else { + Elts.push_back(ConstantInt::get(Type::getInt32Ty(SVI.getContext()), + NewMask[i])); + } + } + return new ShuffleVectorInst(LHS, LSVI->getOperand(1), + ConstantVector::get(Elts)); + } + } return MadeChange ? &SVI : 0; } -