Index: llvm/trunk/include/llvm/CodeGen/SelectionDAGNodes.h =================================================================== --- llvm/trunk/include/llvm/CodeGen/SelectionDAGNodes.h +++ llvm/trunk/include/llvm/CodeGen/SelectionDAGNodes.h @@ -328,6 +328,7 @@ bool NoInfs : 1; bool NoSignedZeros : 1; bool AllowReciprocal : 1; + bool VectorReduction : 1; public: /// Default constructor turns off all optimization flags. @@ -340,6 +341,7 @@ NoInfs = false; NoSignedZeros = false; AllowReciprocal = false; + VectorReduction = false; } // These are mutators for each flag. @@ -351,6 +353,7 @@ void setNoInfs(bool b) { NoInfs = b; } void setNoSignedZeros(bool b) { NoSignedZeros = b; } void setAllowReciprocal(bool b) { AllowReciprocal = b; } + void setVectorReduction(bool b) { VectorReduction = b; } // These are accessors for each flag. bool hasNoUnsignedWrap() const { return NoUnsignedWrap; } @@ -361,6 +364,7 @@ bool hasNoInfs() const { return NoInfs; } bool hasNoSignedZeros() const { return NoSignedZeros; } bool hasAllowReciprocal() const { return AllowReciprocal; } + bool hasVectorReduction() const { return VectorReduction; } /// Return a raw encoding of the flags. /// This function should only be used to add data to the NodeID value. Index: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp =================================================================== --- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp +++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp @@ -2308,6 +2308,125 @@ visitBinary(I, ISD::FSUB); } +/// Checks if the given instruction performs a vector reduction, in which case +/// we have the freedom to alter the elements in the result as long as the +/// reduction of them stays unchanged. +static bool isVectorReductionOp(const User *I) { + const Instruction *Inst = dyn_cast(I); + if (!Inst || !Inst->getType()->isVectorTy()) + return false; + + auto OpCode = Inst->getOpcode(); + switch (OpCode) { + case Instruction::Add: + case Instruction::Mul: + case Instruction::And: + case Instruction::Or: + case Instruction::Xor: + break; + case Instruction::FAdd: + case Instruction::FMul: + if (const FPMathOperator *FPOp = dyn_cast(Inst)) + if (FPOp->getFastMathFlags().unsafeAlgebra()) + break; + // Fall through. + default: + return false; + } + + unsigned ElemNum = Inst->getType()->getVectorNumElements(); + unsigned ElemNumToReduce = ElemNum; + + // Do DFS search on the def-use chain from the given instruction. We only + // allow four kinds of operations during the search until we reach the + // instruction that extracts the first element from the vector: + // + // 1. The reduction operation of the same opcode as the given instruction. + // + // 2. PHI node. + // + // 3. ShuffleVector instruction together with a reduction operation that + // does a partial reduction. + // + // 4. ExtractElement that extracts the first element from the vector, and we + // stop searching the def-use chain here. + // + // 3 & 4 above perform a reduction on all elements of the vector. We push defs + // from 1-3 to the stack to continue the DFS. The given instruction is not + // a reduction operation if we meet any other instructions other than those + // listed above. + + SmallVector UsersToVisit{Inst}; + SmallPtrSet Visited; + bool ReduxExtracted = false; + + while (!UsersToVisit.empty()) { + auto User = UsersToVisit.back(); + UsersToVisit.pop_back(); + if (!Visited.insert(User).second) + continue; + + for (const auto &U : User->users()) { + auto Inst = dyn_cast(U); + if (!Inst) + return false; + + if (Inst->getOpcode() == OpCode || isa(U)) { + if (const FPMathOperator *FPOp = dyn_cast(Inst)) + if (!isa(FPOp) && !FPOp->getFastMathFlags().unsafeAlgebra()) + return false; + UsersToVisit.push_back(U); + } else if (const ShuffleVectorInst *ShufInst = + dyn_cast(U)) { + // Detect the following pattern: A ShuffleVector instruction together + // with a reduction that do partial reduction on the first and second + // ElemNumToReduce / 2 elements, and store the result in + // ElemNumToReduce / 2 elements in another vector. + + if (ElemNumToReduce == 1) + return false; + if (!isa(U->getOperand(1))) + return false; + for (unsigned i = 0; i < ElemNumToReduce / 2; ++i) + if (ShufInst->getMaskValue(i) != int(i + ElemNumToReduce / 2)) + return false; + for (unsigned i = ElemNumToReduce / 2; i < ElemNum; ++i) + if (ShufInst->getMaskValue(i) != -1) + return false; + + // There is only one user of this ShuffleVector instruction, which must + // be a reduction operation. + if (!U->hasOneUse()) + return false; + + auto U2 = dyn_cast(*U->user_begin()); + if (!U2 || U2->getOpcode() != OpCode) + return false; + + // Check operands of the reduction operation. + if ((U2->getOperand(0) == U->getOperand(0) && U2->getOperand(1) == U) || + (U2->getOperand(1) == U->getOperand(0) && U2->getOperand(0) == U)) { + UsersToVisit.push_back(U2); + ElemNumToReduce /= 2; + } else + return false; + } else if (isa(U)) { + // At this moment we should have reduced all elements in the vector. + if (ElemNumToReduce != 1) + return false; + + const ConstantInt *Val = dyn_cast(U->getOperand(1)); + if (!Val || Val->getZExtValue() != 0) + return false; + + ReduxExtracted = true; + } else + return false; + } + } + return ReduxExtracted; +} + void SelectionDAGBuilder::visitBinary(const User &I, unsigned OpCode) { SDValue Op1 = getValue(I.getOperand(0)); SDValue Op2 = getValue(I.getOperand(1)); @@ -2315,6 +2434,7 @@ bool nuw = false; bool nsw = false; bool exact = false; + bool vec_redux = false; FastMathFlags FMF; if (const OverflowingBinaryOperator *OFBinOp = @@ -2328,10 +2448,16 @@ if (const FPMathOperator *FPOp = dyn_cast(&I)) FMF = FPOp->getFastMathFlags(); + if (isVectorReductionOp(&I)) { + vec_redux = true; + DEBUG(dbgs() << "Detected a reduction operation:" << I << "\n"); + } + SDNodeFlags Flags; Flags.setExact(exact); Flags.setNoSignedWrap(nsw); Flags.setNoUnsignedWrap(nuw); + Flags.setVectorReduction(vec_redux); if (EnableFMFInDAG) { Flags.setAllowReciprocal(FMF.allowReciprocal()); Flags.setNoInfs(FMF.noInfs()); Index: llvm/trunk/test/CodeGen/Generic/vector-redux.ll =================================================================== --- llvm/trunk/test/CodeGen/Generic/vector-redux.ll +++ llvm/trunk/test/CodeGen/Generic/vector-redux.ll @@ -0,0 +1,85 @@ +; RUN: llc < %s -debug-only=isel -o /dev/null 2>&1 | FileCheck %s +; REQUIRES: asserts + +@a = global [1024 x i32] zeroinitializer, align 16 + +define float @reduce_add_float(float* nocapture readonly %a) { +; CHECK-LABEL: reduce_add_float +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; CHECK: Detected a reduction operation: {{.*}} fadd fast +; +entry: + br label %vector.body + +vector.body: + %index = phi i64 [ 0, %entry ], [ %index.next.4, %vector.body ] + %vec.phi = phi <4 x float> [ zeroinitializer, %entry ], [ %28, %vector.body ] + %vec.phi9 = phi <4 x float> [ zeroinitializer, %entry ], [ %29, %vector.body ] + %0 = getelementptr inbounds float, float* %a, i64 %index + %1 = bitcast float* %0 to <4 x float>* + %wide.load = load <4 x float>, <4 x float>* %1, align 4 + %2 = getelementptr float, float* %0, i64 4 + %3 = bitcast float* %2 to <4 x float>* + %wide.load10 = load <4 x float>, <4 x float>* %3, align 4 + %4 = fadd fast <4 x float> %wide.load, %vec.phi + %5 = fadd fast <4 x float> %wide.load10, %vec.phi9 + %index.next = add nuw nsw i64 %index, 8 + %6 = getelementptr inbounds float, float* %a, i64 %index.next + %7 = bitcast float* %6 to <4 x float>* + %wide.load.1 = load <4 x float>, <4 x float>* %7, align 4 + %8 = getelementptr float, float* %6, i64 4 + %9 = bitcast float* %8 to <4 x float>* + %wide.load10.1 = load <4 x float>, <4 x float>* %9, align 4 + %10 = fadd fast <4 x float> %wide.load.1, %4 + %11 = fadd fast <4 x float> %wide.load10.1, %5 + %index.next.1 = add nsw i64 %index, 16 + %12 = getelementptr inbounds float, float* %a, i64 %index.next.1 + %13 = bitcast float* %12 to <4 x float>* + %wide.load.2 = load <4 x float>, <4 x float>* %13, align 4 + %14 = getelementptr float, float* %12, i64 4 + %15 = bitcast float* %14 to <4 x float>* + %wide.load10.2 = load <4 x float>, <4 x float>* %15, align 4 + %16 = fadd fast <4 x float> %wide.load.2, %10 + %17 = fadd fast <4 x float> %wide.load10.2, %11 + %index.next.2 = add nsw i64 %index, 24 + %18 = getelementptr inbounds float, float* %a, i64 %index.next.2 + %19 = bitcast float* %18 to <4 x float>* + %wide.load.3 = load <4 x float>, <4 x float>* %19, align 4 + %20 = getelementptr float, float* %18, i64 4 + %21 = bitcast float* %20 to <4 x float>* + %wide.load10.3 = load <4 x float>, <4 x float>* %21, align 4 + %22 = fadd fast <4 x float> %wide.load.3, %16 + %23 = fadd fast <4 x float> %wide.load10.3, %17 + %index.next.3 = add nsw i64 %index, 32 + %24 = getelementptr inbounds float, float* %a, i64 %index.next.3 + %25 = bitcast float* %24 to <4 x float>* + %wide.load.4 = load <4 x float>, <4 x float>* %25, align 4 + %26 = getelementptr float, float* %24, i64 4 + %27 = bitcast float* %26 to <4 x float>* + %wide.load10.4 = load <4 x float>, <4 x float>* %27, align 4 + %28 = fadd fast <4 x float> %wide.load.4, %22 + %29 = fadd fast <4 x float> %wide.load10.4, %23 + %index.next.4 = add nsw i64 %index, 40 + %30 = icmp eq i64 %index.next.4, 1000 + br i1 %30, label %middle.block, label %vector.body + +middle.block: + %.lcssa15 = phi <4 x float> [ %29, %vector.body ] + %.lcssa = phi <4 x float> [ %28, %vector.body ] + %bin.rdx = fadd fast <4 x float> %.lcssa15, %.lcssa + %rdx.shuf = shufflevector <4 x float> %bin.rdx, <4 x float> undef, <4 x i32> + %bin.rdx11 = fadd fast <4 x float> %bin.rdx, %rdx.shuf + %rdx.shuf12 = shufflevector <4 x float> %bin.rdx11, <4 x float> undef, <4 x i32> + %bin.rdx13 = fadd fast <4 x float> %bin.rdx11, %rdx.shuf12 + %31 = extractelement <4 x float> %bin.rdx13, i32 0 + ret float %31 +}