[Hexagon] Remove unnecessary argument sign extends

llvm-svn: 250724

llvm/lib/Target/Hexagon/CMakeLists.txt

@@ -35,6 +35,7 @@ add_llvm_target(HexagonCodeGen
   HexagonMachineScheduler.cpp
   HexagonMCInstLower.cpp
   HexagonNewValueJump.cpp
+  HexagonOptimizeSZextends.cpp
   HexagonPeephole.cpp
   HexagonRegisterInfo.cpp
   HexagonSelectionDAGInfo.cpp

llvm/lib/Target/Hexagon/HexagonOptimizeSZextends.cpp

@@ -0,0 +1,150 @@
+//===- HexagonOptimizeSZextends.cpp - Remove unnecessary argument extends -===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Pass that removes sign extends for function parameters. These parameters
+// are already sign extended by the caller per Hexagon's ABI
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineFunctionAnalysis.h"
+#include "llvm/CodeGen/StackProtector.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Scalar.h"
+
+#include "Hexagon.h"
+
+using namespace llvm;
+
+namespace llvm {
+  FunctionPass *createHexagonOptimizeSZextends();
+  void initializeHexagonOptimizeSZextendsPass(PassRegistry&);
+}
+
+namespace {
+  struct HexagonOptimizeSZextends : public FunctionPass {
+  public:
+    static char ID;
+    HexagonOptimizeSZextends() : FunctionPass(ID) {
+      initializeHexagonOptimizeSZextendsPass(*PassRegistry::getPassRegistry());
+    }
+    bool runOnFunction(Function &F) override;
+
+    const char *getPassName() const override {
+      return "Remove sign extends";
+    }
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.addRequired<MachineFunctionAnalysis>();
+      AU.addPreserved<MachineFunctionAnalysis>();
+      AU.addPreserved<StackProtector>();
+      FunctionPass::getAnalysisUsage(AU);
+    }
+
+    bool intrinsicAlreadySextended(Intrinsic::ID IntID);
+  };
+}
+
+char HexagonOptimizeSZextends::ID = 0;
+
+INITIALIZE_PASS(HexagonOptimizeSZextends, "reargs",
+                "Remove Sign and Zero Extends for Args", false, false)
+
+bool HexagonOptimizeSZextends::intrinsicAlreadySextended(Intrinsic::ID IntID) {
+  switch(IntID) {
+    case llvm::Intrinsic::hexagon_A2_addh_l16_sat_ll:
+      return true;
+    default:
+      break;
+  }
+  return false;
+}
+
+bool HexagonOptimizeSZextends::runOnFunction(Function &F) {
+  unsigned Idx = 1;
+  // Try to optimize sign extends in formal parameters. It's relying on
+  // callee already sign extending the values. I'm not sure if our ABI
+  // requires callee to sign extend though.
+  for (auto &Arg : F.args()) {
+    if (F.getAttributes().hasAttribute(Idx, Attribute::SExt)) {
+      if (!isa<PointerType>(Arg.getType())) {
+        for (auto UI = Arg.use_begin(); UI != Arg.use_end();) {
+          if (isa<SExtInst>(*UI)) {
+            Instruction* Use = cast<Instruction>(*UI);
+            SExtInst* SI = new SExtInst(&Arg, Use->getType());
+            assert (EVT::getEVT(SI->getType()) ==
+                    (EVT::getEVT(Use->getType())));
+            ++UI;
+            Use->replaceAllUsesWith(SI);
+            Instruction* First = F.getEntryBlock().begin();
+            SI->insertBefore(First);
+            Use->eraseFromParent();
+          } else {
+            ++UI;
+          }
+        }
+      }
+    }
+    ++Idx;
+  }
+
+  // Try to remove redundant sext operations on Hexagon. The hardware
+  // already sign extends many 16 bit intrinsic operations to 32 bits.
+  // For example:
+  // %34 = tail call i32 @llvm.hexagon.A2.addh.l16.sat.ll(i32 %x, i32 %y)
+  // %sext233 = shl i32 %34, 16
+  // %conv52 = ashr exact i32 %sext233, 16
+  for (auto &B : F) {
+    for (auto &I : B) {
+      // Look for arithmetic shift right by 16.
+      BinaryOperator *Ashr = dyn_cast<BinaryOperator>(&I);
+      if (!(Ashr && Ashr->getOpcode() == Instruction::AShr))
+        continue;
+      Value *AshrOp1 = Ashr->getOperand(1);
+      ConstantInt *C = dyn_cast<ConstantInt>(AshrOp1);
+      // Right shifted by 16.
+      if (!(C && C->getSExtValue() == 16))
+        continue;
+
+      // The first operand of Ashr comes from logical shift left.
+      Instruction *Shl = dyn_cast<Instruction>(Ashr->getOperand(0));
+      if (!(Shl && Shl->getOpcode() == Instruction::Shl))
+        continue;
+      Value *Intr = Shl->getOperand(0);
+      Value *ShlOp1 = Shl->getOperand(1);
+      C = dyn_cast<ConstantInt>(ShlOp1);
+      // Left shifted by 16.
+      if (!(C && C->getSExtValue() == 16))
+        continue;
+
+      // The first operand of Shl comes from an intrinsic.
+      if (IntrinsicInst *I = dyn_cast<IntrinsicInst>(Intr)) {
+        if (!intrinsicAlreadySextended(I->getIntrinsicID()))
+          continue;
+        // All is well. Replace all uses of AShr with I.
+        for (auto UI = Ashr->user_begin(), UE = Ashr->user_end();
+             UI != UE; ++UI) {
+          const Use &TheUse = UI.getUse();
+          if (Instruction *J = dyn_cast<Instruction>(TheUse.getUser())) {
+            J->replaceUsesOfWith(Ashr, I);
+          }
+        }
+      }
+    }
+  }
+
+  return true;
+}
+
+
+FunctionPass *llvm::createHexagonOptimizeSZextends() {
+  return new HexagonOptimizeSZextends();
+}

llvm/lib/Target/Hexagon/HexagonTargetMachine.cpp

@@ -100,6 +100,7 @@ namespace llvm {
   FunctionPass *createHexagonISelDag(HexagonTargetMachine &TM,
                                      CodeGenOpt::Level OptLevel);
   FunctionPass *createHexagonNewValueJump();
+  FunctionPass *createHexagonOptimizeSZextends();
   FunctionPass *createHexagonPacketizer();
   FunctionPass *createHexagonPeephole();
   FunctionPass *createHexagonSplitConst32AndConst64();
@@ -213,6 +214,9 @@ bool HexagonPassConfig::addInstSelector() {
   HexagonTargetMachine &TM = getHexagonTargetMachine();
   bool NoOpt = (getOptLevel() == CodeGenOpt::None);
 
+  if (!NoOpt)
+    addPass(createHexagonOptimizeSZextends());
+
   addPass(createHexagonISelDag(TM, getOptLevel()));
 
   if (!NoOpt) {