[Hexagon] Generate "extract" instructions more aggressively

Generate extract instructions (via intrinsics) before the DAG combiner
folds shifts into unrecognizable forms.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242163 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Hexagon/CMakeLists.txt

@@ -22,6 +22,7 @@ add_llvm_target(HexagonCodeGen
   HexagonExpandPredSpillCode.cpp
   HexagonFixupHwLoops.cpp
   HexagonFrameLowering.cpp
+  HexagonGenExtract.cpp
   HexagonGenInsert.cpp
   HexagonHardwareLoops.cpp
   HexagonInstrInfo.cpp

lib/Target/Hexagon/HexagonGenExtract.cpp

@@ -0,0 +1,259 @@
+//===--- HexagonGenExtract.cpp --------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/CodeGen/MachineFunctionAnalysis.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/PatternMatch.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+static cl::opt<unsigned> ExtractCutoff("extract-cutoff", cl::init(~0U),
+  cl::Hidden, cl::desc("Cutoff for generating \"extract\""
+  " instructions"));
+
+// This prevents generating extract instructions that have the offset of 0.
+// One of the reasons for "extract" is to put a sequence of bits in a regis-
+// ter, starting at offset 0 (so that these bits can then be used by an
+// "insert"). If the bits are already at offset 0, it is better not to gene-
+// rate "extract", since logical bit operations can be merged into compound
+// instructions (as opposed to "extract").
+static cl::opt<bool> NoSR0("extract-nosr0", cl::init(true), cl::Hidden,
+  cl::desc("No extract instruction with offset 0"));
+
+static cl::opt<bool> NeedAnd("extract-needand", cl::init(true), cl::Hidden,
+  cl::desc("Require & in extract patterns"));
+
+namespace llvm {
+  void initializeHexagonGenExtractPass(PassRegistry&);
+  FunctionPass *createHexagonGenExtract();
+}
+
+
+namespace {
+  class HexagonGenExtract : public FunctionPass {
+  public:
+    static char ID;
+    HexagonGenExtract() : FunctionPass(ID), ExtractCount(0) {
+      initializeHexagonGenExtractPass(*PassRegistry::getPassRegistry());
+    }
+    virtual const char *getPassName() const override {
+      return "Hexagon generate \"extract\" instructions";
+    }
+    virtual bool runOnFunction(Function &F) override;
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.addRequired<DominatorTreeWrapperPass>();
+      AU.addPreserved<DominatorTreeWrapperPass>();
+      AU.addPreserved<MachineFunctionAnalysis>();
+      FunctionPass::getAnalysisUsage(AU);
+    }
+  private:
+    bool visitBlock(BasicBlock *B);
+    bool convert(Instruction *In);
+
+    unsigned ExtractCount;
+    DominatorTree *DT;
+  };
+
+  char HexagonGenExtract::ID = 0;
+}
+
+INITIALIZE_PASS_BEGIN(HexagonGenExtract, "hextract", "Hexagon generate "
+  "\"extract\" instructions", false, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_END(HexagonGenExtract, "hextract", "Hexagon generate "
+  "\"extract\" instructions", false, false)
+
+
+bool HexagonGenExtract::convert(Instruction *In) {
+  using namespace PatternMatch;
+  Value *BF = 0;
+  ConstantInt *CSL = 0, *CSR = 0, *CM = 0;
+  BasicBlock *BB = In->getParent();
+  LLVMContext &Ctx = BB->getContext();
+  bool LogicalSR;
+
+  // (and (shl (lshr x, #sr), #sl), #m)
+  LogicalSR = true;
+  bool Match = match(In, m_And(m_Shl(m_LShr(m_Value(BF), m_ConstantInt(CSR)),
+                               m_ConstantInt(CSL)),
+                         m_ConstantInt(CM)));
+
+  if (!Match) {
+    // (and (shl (ashr x, #sr), #sl), #m)
+    LogicalSR = false;
+    Match = match(In, m_And(m_Shl(m_AShr(m_Value(BF), m_ConstantInt(CSR)),
+                            m_ConstantInt(CSL)),
+                      m_ConstantInt(CM)));
+  }
+  if (!Match) {
+    // (and (shl x, #sl), #m)
+    LogicalSR = true;
+    CSR = ConstantInt::get(Type::getInt32Ty(Ctx), 0);
+    Match = match(In, m_And(m_Shl(m_Value(BF), m_ConstantInt(CSL)),
+                      m_ConstantInt(CM)));
+    if (Match && NoSR0)
+      return false;
+  }
+  if (!Match) {
+    // (and (lshr x, #sr), #m)
+    LogicalSR = true;
+    CSL = ConstantInt::get(Type::getInt32Ty(Ctx), 0);
+    Match = match(In, m_And(m_LShr(m_Value(BF), m_ConstantInt(CSR)),
+                            m_ConstantInt(CM)));
+  }
+  if (!Match) {
+    // (and (ashr x, #sr), #m)
+    LogicalSR = false;
+    CSL = ConstantInt::get(Type::getInt32Ty(Ctx), 0);
+    Match = match(In, m_And(m_AShr(m_Value(BF), m_ConstantInt(CSR)),
+                            m_ConstantInt(CM)));
+  }
+  if (!Match) {
+    CM = 0;
+    // (shl (lshr x, #sr), #sl)
+    LogicalSR = true;
+    Match = match(In, m_Shl(m_LShr(m_Value(BF), m_ConstantInt(CSR)),
+                            m_ConstantInt(CSL)));
+  }
+  if (!Match) {
+    CM = 0;
+    // (shl (ashr x, #sr), #sl)
+    LogicalSR = false;
+    Match = match(In, m_Shl(m_AShr(m_Value(BF), m_ConstantInt(CSR)),
+                            m_ConstantInt(CSL)));
+  }
+  if (!Match)
+    return false;
+
+  Type *Ty = BF->getType();
+  if (!Ty->isIntegerTy())
+    return false;
+  unsigned BW = Ty->getPrimitiveSizeInBits();
+  if (BW != 32 && BW != 64)
+    return false;
+
+  uint32_t SR = CSR->getZExtValue();
+  uint32_t SL = CSL->getZExtValue();
+
+  if (!CM) {
+    // If there was no and, and the shift left did not remove all potential
+    // sign bits created by the shift right, then extractu cannot reproduce
+    // this value.
+    if (!LogicalSR && (SR > SL))
+      return false;
+    APInt A = APInt(BW, ~0ULL).lshr(SR).shl(SL);
+    CM = ConstantInt::get(Ctx, A);
+  }
+
+  // CM is the shifted-left mask. Shift it back right to remove the zero
+  // bits on least-significant positions.
+  APInt M = CM->getValue().lshr(SL);
+  uint32_t T = M.countTrailingOnes();
+
+  // During the shifts some of the bits will be lost. Calculate how many
+  // of the original value will remain after shift right and then left.
+  uint32_t U = BW - std::max(SL, SR);
+  // The width of the extracted field is the minimum of the original bits
+  // that remain after the shifts and the number of contiguous 1s in the mask.
+  uint32_t W = std::min(U, T);
+  if (W == 0)
+    return false;
+
+  // Check if the extracted bits are contained within the mask that it is
+  // and-ed with. The extract operation will copy these bits, and so the
+  // mask cannot any holes in it that would clear any of the bits of the
+  // extracted field.
+  if (!LogicalSR) {
+    // If the shift right was arithmetic, it could have included some 1 bits.
+    // It is still ok to generate extract, but only if the mask eliminates
+    // those bits (i.e. M does not have any bits set beyond U).
+    APInt C = APInt::getHighBitsSet(BW, BW-U);
+    if (M.intersects(C) || !APIntOps::isMask(W, M))
+      return false;
+  } else {
+    // Check if M starts with a contiguous sequence of W times 1 bits. Get
+    // the low U bits of M (which eliminates the 0 bits shifted in on the
+    // left), and check if the result is APInt's "mask":
+    if (!APIntOps::isMask(W, M.getLoBits(U)))
+      return false;
+  }
+
+  IRBuilder<> IRB(BB, In);
+  Intrinsic::ID IntId = (BW == 32) ? Intrinsic::hexagon_S2_extractu
+                                   : Intrinsic::hexagon_S2_extractup;
+  Module *Mod = BB->getParent()->getParent();
+  Value *ExtF = Intrinsic::getDeclaration(Mod, IntId);
+  Value *NewIn = IRB.CreateCall(ExtF, {BF, IRB.getInt32(W), IRB.getInt32(SR)});
+  if (SL != 0)
+    NewIn = IRB.CreateShl(NewIn, SL, CSL->getName());
+  In->replaceAllUsesWith(NewIn);
+  return true;
+}
+
+
+bool HexagonGenExtract::visitBlock(BasicBlock *B) {
+  // Depth-first, bottom-up traversal.
+  DomTreeNode *DTN = DT->getNode(B);
+  typedef GraphTraits<DomTreeNode*> GTN;
+  typedef GTN::ChildIteratorType Iter;
+  for (Iter I = GTN::child_begin(DTN), E = GTN::child_end(DTN); I != E; ++I)
+    visitBlock((*I)->getBlock());
+
+  // Allow limiting the number of generated extracts for debugging purposes.
+  bool HasCutoff = ExtractCutoff.getPosition();
+  unsigned Cutoff = ExtractCutoff;
+
+  bool Changed = false;
+  BasicBlock::iterator I = std::prev(B->end()), NextI, Begin = B->begin();
+  while (true) {
+    if (HasCutoff && (ExtractCount >= Cutoff))
+      return Changed;
+    bool Last = (I == Begin);
+    if (!Last)
+      NextI = std::prev(I);
+    Instruction *In = &*I;
+    bool Done = convert(In);
+    if (HasCutoff && Done)
+      ExtractCount++;
+    Changed |= Done;
+    if (Last)
+      break;
+    I = NextI;
+  }
+  return Changed;
+}
+
+
+bool HexagonGenExtract::runOnFunction(Function &F) {
+  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+  bool Changed;
+
+  // Traverse the function bottom-up, to see super-expressions before their
+  // sub-expressions.
+  BasicBlock *Entry = GraphTraits<Function*>::getEntryNode(&F);
+  Changed = visitBlock(Entry);
+
+  return Changed;
+}
+
+
+FunctionPass *llvm::createHexagonGenExtract() {
+  return new HexagonGenExtract();
+}

lib/Target/Hexagon/HexagonTargetMachine.cpp

@@ -43,6 +43,8 @@ static cl::opt<bool> EnableGenInsert("hexagon-insert", cl::init(true),
 static cl::opt<bool> EnableCommGEP("hexagon-commgep", cl::init(true),
   cl::Hidden, cl::ZeroOrMore, cl::desc("Enable commoning of GEP instructions"));
 
+static cl::opt<bool> EnableGenExtract("hexagon-extract", cl::init(true),
+  cl::Hidden, cl::desc("Generate \"extract\" instructions"));
 
 /// HexagonTargetMachineModule - Note that this is used on hosts that
 /// cannot link in a library unless there are references into the
@@ -66,24 +68,22 @@ SchedCustomRegistry("hexagon", "Run Hexagon's custom scheduler",
                     createVLIWMachineSched);
 
 namespace llvm {
-  FunctionPass *createHexagonCommonGEP();
-  FunctionPass *createHexagonExpandCondsets();
-  FunctionPass *createHexagonISelDag(HexagonTargetMachine &TM,
-                                     CodeGenOpt::Level OptLevel);
-  FunctionPass *createHexagonDelaySlotFillerPass(const TargetMachine &TM);
-  FunctionPass *createHexagonRemoveExtendArgs(const HexagonTargetMachine &TM);
   FunctionPass *createHexagonCFGOptimizer();
-
-  FunctionPass *createHexagonSplitConst32AndConst64();
+  FunctionPass *createHexagonCommonGEP();
+  FunctionPass *createHexagonCopyToCombine();
+  FunctionPass *createHexagonExpandCondsets();
   FunctionPass *createHexagonExpandPredSpillCode();
+  FunctionPass *createHexagonFixupHwLoops();
+  FunctionPass *createHexagonGenExtract();
   FunctionPass *createHexagonGenInsert();
   FunctionPass *createHexagonHardwareLoops();
-  FunctionPass *createHexagonPeephole();
-  FunctionPass *createHexagonFixupHwLoops();
+  FunctionPass *createHexagonISelDag(HexagonTargetMachine &TM,
+                                     CodeGenOpt::Level OptLevel);
   FunctionPass *createHexagonNewValueJump();
-  FunctionPass *createHexagonCopyToCombine();
   FunctionPass *createHexagonPacketizer();
-  FunctionPass *createHexagonNewValueJump();
+  FunctionPass *createHexagonPeephole();
+  FunctionPass *createHexagonRemoveExtendArgs(const HexagonTargetMachine &TM);
+  FunctionPass *createHexagonSplitConst32AndConst64();
 } // end namespace llvm;
 
 /// HexagonTargetMachine ctor - Create an ILP32 architecture model.
@@ -147,8 +147,13 @@ void HexagonPassConfig::addIRPasses() {
   bool NoOpt = (getOptLevel() == CodeGenOpt::None);
 
   addPass(createAtomicExpandPass(TM));
-  if (!NoOpt && EnableCommGEP)
-    addPass(createHexagonCommonGEP());
+  if (!NoOpt) {
+    if (EnableCommGEP)
+      addPass(createHexagonCommonGEP());
+    // Replace certain combinations of shifts and ands with extracts.
+    if (EnableGenExtract)
+      addPass(createHexagonGenExtract());
+  }
 }
 
 bool HexagonPassConfig::addInstSelector() {

test/CodeGen/Hexagon/extract-basic.ll

@@ -0,0 +1,76 @@
+; RUN: llc -O2 -march=hexagon < %s | FileCheck %s
+
+; CHECK-DAG: extractu(r{{[0-9]*}}, #3, #4)
+; CHECK-DAG: extractu(r{{[0-9]*}}, #8, #7)
+; CHECK-DAG: extractu(r{{[0-9]*}}, #8, #16)
+
+; C source:
+; typedef struct {
+;   unsigned x1:3;
+;   unsigned x2:7;
+;   unsigned x3:8;
+;   unsigned x4:12;
+;   unsigned x5:2;
+; } structx_t;
+;
+; typedef struct {
+;   unsigned y1:4;
+;   unsigned y2:3;
+;   unsigned y3:9;
+;   unsigned y4:8;
+;   unsigned y5:8;
+; } structy_t;
+;
+; void foo(structx_t *px, structy_t *py) {
+;   px->x1 = py->y1;
+;   px->x2 = py->y2;
+;   px->x3 = py->y3;
+;   px->x4 = py->y4;
+;   px->x5 = py->y5;
+; }
+
+target datalayout = "e-p:32:32:32-i64:64:64-i32:32:32-i16:16:16-i1:32:32-f64:64:64-f32:32:32-v64:64:64-v32:32:32-a0:0-n16:32"
+target triple = "hexagon"
+
+%struct.structx_t = type { i8, i8, i8, i8 }
+%struct.structy_t = type { i8, i8, i8, i8 }
+
+define void @foo(%struct.structx_t* nocapture %px, %struct.structy_t* nocapture %py) nounwind {
+entry:
+  %0 = bitcast %struct.structy_t* %py to i32*
+  %1 = load i32, i32* %0, align 4
+  %bf.value = and i32 %1, 7
+  %2 = bitcast %struct.structx_t* %px to i32*
+  %3 = load i32, i32* %2, align 4
+  %4 = and i32 %3, -8
+  %5 = or i32 %4, %bf.value
+  store i32 %5, i32* %2, align 4
+  %6 = load i32, i32* %0, align 4
+  %7 = lshr i32 %6, 4
+  %bf.clear1 = shl nuw nsw i32 %7, 3
+  %8 = and i32 %bf.clear1, 56
+  %9 = and i32 %5, -1017
+  %10 = or i32 %8, %9
+  store i32 %10, i32* %2, align 4
+  %11 = load i32, i32* %0, align 4
+  %12 = lshr i32 %11, 7
+  %bf.value4 = shl i32 %12, 10
+  %13 = and i32 %bf.value4, 261120
+  %14 = and i32 %10, -262081
+  %15 = or i32 %14, %13
+  store i32 %15, i32* %2, align 4
+  %16 = load i32, i32* %0, align 4
+  %17 = lshr i32 %16, 16
+  %bf.clear5 = shl i32 %17, 18
+  %18 = and i32 %bf.clear5, 66846720
+  %19 = and i32 %15, -1073480641
+  %20 = or i32 %19, %18
+  store i32 %20, i32* %2, align 4
+  %21 = load i32, i32* %0, align 4
+  %22 = lshr i32 %21, 24
+  %23 = shl i32 %22, 30
+  %24 = and i32 %20, 67107903
+  %25 = or i32 %24, %23
+  store i32 %25, i32* %2, align 4
+  ret void
+}

test/CodeGen/Hexagon/fusedandshift.ll

@@ -1,5 +1,6 @@
-; RUN: llc -march=hexagon -mcpu=hexagonv4  < %s | FileCheck %s
+; RUN: llc -march=hexagon -hexagon-extract=0 < %s | FileCheck %s
 ; Check that we generate fused logical and with shift instruction.
+; Disable "extract" generation, since it may eliminate the and/lsr.
 
 ; CHECK: r{{[0-9]+}} = and(#15, lsr(r{{[0-9]+}}, #{{[0-9]+}})