Rebased PNaCl localmods in LLVM to 223109

lib/Transforms/NaCl/ExpandShuffleVector.cpp

+//===- ExpandShuffleVector.cpp - shufflevector to {insert/extract}element -===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Replace all shufflevector instructions by insertelement / extractelement.
+// BackendCanonicalize is able to reconstruct the shufflevector.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/NaCl.h"
+
+using namespace llvm;
+
+namespace {
+class ExpandShuffleVector : public BasicBlockPass {
+public:
+  static char ID; // Pass identification, replacement for typeid
+  ExpandShuffleVector() : BasicBlockPass(ID), M(0) {
+    initializeExpandShuffleVectorPass(*PassRegistry::getPassRegistry());
+  }
+  using BasicBlockPass::doInitialization;
+  bool doInitialization(Module &Mod) override {
+    M = &Mod;
+    return false; // Unchanged.
+  }
+  bool runOnBasicBlock(BasicBlock &BB) override;
+
+private:
+  const Module *M;
+  void Expand(ShuffleVectorInst *Shuf, Type *Int32);
+};
+}
+
+char ExpandShuffleVector::ID = 0;
+INITIALIZE_PASS(
+    ExpandShuffleVector, "expand-shufflevector",
+    "Expand shufflevector instructions into insertelement and extractelement",
+    false, false)
+
+void ExpandShuffleVector::Expand(ShuffleVectorInst *Shuf, Type *Int32) {
+  Value *L = Shuf->getOperand(0);
+  Value *R = Shuf->getOperand(1);
+  assert(L->getType() == R->getType());
+  VectorType *SrcVecTy = cast<VectorType>(L->getType());
+  VectorType *DstVecTy = Shuf->getType();
+  Type *ElemTy = DstVecTy->getElementType();
+  SmallVector<int, 16> Mask = Shuf->getShuffleMask();
+  unsigned NumSrcElems = SrcVecTy->getNumElements();
+  unsigned NumDstElems = Mask.size();
+
+  // Start with an undefined vector, extract each element from either L
+  // or R according to the Mask, and insert it into contiguous element
+  // locations in the result vector.
+  //
+  // The sources for shufflevector must have the same type but the
+  // destination could be a narrower or wider vector with the same
+  // element type.
+  Instruction *ExtractLoc = Shuf;
+  Value *Res = UndefValue::get(DstVecTy);
+  for (unsigned Elem = 0; Elem != NumDstElems; ++Elem) {
+    bool IsUndef =
+        0 > Mask[Elem] || static_cast<unsigned>(Mask[Elem]) >= NumSrcElems * 2;
+    bool IsL = static_cast<unsigned>(Mask[Elem]) < NumSrcElems;
+    Value *From = IsL ? L : R;
+    int Adjustment = IsL ? 0 : NumSrcElems;
+    Constant *ExtractIdx = ConstantInt::get(Int32, Mask[Elem] - Adjustment);
+    Constant *InsertIdx = ConstantInt::get(Int32, Elem);
+    Value *ElemToInsert = IsUndef ? UndefValue::get(ElemTy)
+                                  : (Value *)ExtractElementInst::Create(
+                                        From, ExtractIdx, "", ExtractLoc);
+    Res = InsertElementInst::Create(Res, ElemToInsert, InsertIdx, "", Shuf);
+    if (ExtractLoc == Shuf)
+      // All the extracts should be added just before the first insert we added.
+      ExtractLoc = cast<Instruction>(Res);
+  }
+
+  Shuf->replaceAllUsesWith(Res);
+  Shuf->eraseFromParent();
+}
+
+bool ExpandShuffleVector::runOnBasicBlock(BasicBlock &BB) {
+  Type *Int32 = Type::getInt32Ty(M->getContext());
+  typedef SmallVector<ShuffleVectorInst *, 8> Instructions;
+  Instructions Shufs;
+
+  for (BasicBlock::iterator BBI = BB.begin(); BBI != BB.end(); ++BBI)
+    if (ShuffleVectorInst *S = dyn_cast<ShuffleVectorInst>(&*BBI))
+      Shufs.push_back(S);
+
+  for (Instructions::iterator S = Shufs.begin(), E = Shufs.end(); S != E; ++S)
+    Expand(*S, Int32);
+
+  return !Shufs.empty();
+}
+
+BasicBlockPass *llvm::createExpandShuffleVectorPass() {
+  return new ExpandShuffleVector();
+}