1 files changed, 195 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp b/contrib/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp
new file mode 100644
index 0000000..b4102fe
--- /dev/null
+++ b/contrib/llvm/lib/Transforms/Scalar/LoopInstSimplify.cpp
@@ -0,0 +1,195 @@
+//===- LoopInstSimplify.cpp - Loop Instruction Simplification Pass --------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass performs lightweight instruction simplification on loop bodies.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Transforms/Utils/Local.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "loop-instsimplify"
+
+STATISTIC(NumSimplified, "Number of redundant instructions simplified");
+
+namespace {
+  class LoopInstSimplify : public LoopPass {
+  public:
+    static char ID; // Pass ID, replacement for typeid
+    LoopInstSimplify() : LoopPass(ID) {
+      initializeLoopInstSimplifyPass(*PassRegistry::getPassRegistry());
+    }
+
+    bool runOnLoop(Loop*, LPPassManager&) override;
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.setPreservesCFG();
+      AU.addRequired<AssumptionCacheTracker>();
+      AU.addRequired<LoopInfoWrapperPass>();
+      AU.addRequiredID(LoopSimplifyID);
+      AU.addPreservedID(LoopSimplifyID);
+      AU.addPreservedID(LCSSAID);
+      AU.addPreserved<ScalarEvolutionWrapperPass>();
+      AU.addRequired<TargetLibraryInfoWrapperPass>();
+    }
+  };
+}
+
+char LoopInstSimplify::ID = 0;
+INITIALIZE_PASS_BEGIN(LoopInstSimplify, "loop-instsimplify",
+                "Simplify instructions in loops", false, false)
+INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(LCSSA)
+INITIALIZE_PASS_END(LoopInstSimplify, "loop-instsimplify",
+                "Simplify instructions in loops", false, false)
+
+Pass *llvm::createLoopInstSimplifyPass() {
+  return new LoopInstSimplify();
+}
+
+bool LoopInstSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
+  if (skipOptnoneFunction(L))
+    return false;
+
+  DominatorTreeWrapperPass *DTWP =
+      getAnalysisIfAvailable<DominatorTreeWrapperPass>();
+  DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
+  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+  const TargetLibraryInfo *TLI =
+      &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+  auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(
+      *L->getHeader()->getParent());
+
+  SmallVector<BasicBlock*, 8> ExitBlocks;
+  L->getUniqueExitBlocks(ExitBlocks);
+  array_pod_sort(ExitBlocks.begin(), ExitBlocks.end());
+
+  SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;
+
+  // The bit we are stealing from the pointer represents whether this basic
+  // block is the header of a subloop, in which case we only process its phis.
+  typedef PointerIntPair<BasicBlock*, 1> WorklistItem;
+  SmallVector<WorklistItem, 16> VisitStack;
+  SmallPtrSet<BasicBlock*, 32> Visited;
+
+  bool Changed = false;
+  bool LocalChanged;
+  do {
+    LocalChanged = false;
+
+    VisitStack.clear();
+    Visited.clear();
+
+    VisitStack.push_back(WorklistItem(L->getHeader(), false));
+
+    while (!VisitStack.empty()) {
+      WorklistItem Item = VisitStack.pop_back_val();
+      BasicBlock *BB = Item.getPointer();
+      bool IsSubloopHeader = Item.getInt();
+      const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
+
+      // Simplify instructions in the current basic block.
+      for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
+        Instruction *I = &*BI++;
+
+        // The first time through the loop ToSimplify is empty and we try to
+        // simplify all instructions. On later iterations ToSimplify is not
+        // empty and we only bother simplifying instructions that are in it.
+        if (!ToSimplify->empty() && !ToSimplify->count(I))
+          continue;
+
+        // Don't bother simplifying unused instructions.
+        if (!I->use_empty()) {
+          Value *V = SimplifyInstruction(I, DL, TLI, DT, &AC);
+          if (V && LI->replacementPreservesLCSSAForm(I, V)) {
+            // Mark all uses for resimplification next time round the loop.
+            for (User *U : I->users())
+              Next->insert(cast<Instruction>(U));
+
+            I->replaceAllUsesWith(V);
+            LocalChanged = true;
+            ++NumSimplified;
+          }
+        }
+        bool res = RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
+        if (res) {
+          // RecursivelyDeleteTriviallyDeadInstruction can remove
+          // more than one instruction, so simply incrementing the
+          // iterator does not work. When instructions get deleted
+          // re-iterate instead.
+          BI = BB->begin(); BE = BB->end();
+          LocalChanged |= res;
+        }
+
+        if (IsSubloopHeader && !isa<PHINode>(I))
+          break;
+      }
+
+      // Add all successors to the worklist, except for loop exit blocks and the
+      // bodies of subloops. We visit the headers of loops so that we can process
+      // their phis, but we contract the rest of the subloop body and only follow
+      // edges leading back to the original loop.
+      for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE;
+           ++SI) {
+        BasicBlock *SuccBB = *SI;
+        if (!Visited.insert(SuccBB).second)
+          continue;
+
+        const Loop *SuccLoop = LI->getLoopFor(SuccBB);
+        if (SuccLoop && SuccLoop->getHeader() == SuccBB
+                     && L->contains(SuccLoop)) {
+          VisitStack.push_back(WorklistItem(SuccBB, true));
+
+          SmallVector<BasicBlock*, 8> SubLoopExitBlocks;
+          SuccLoop->getExitBlocks(SubLoopExitBlocks);
+
+          for (unsigned i = 0; i < SubLoopExitBlocks.size(); ++i) {
+            BasicBlock *ExitBB = SubLoopExitBlocks[i];
+            if (LI->getLoopFor(ExitBB) == L && Visited.insert(ExitBB).second)
+              VisitStack.push_back(WorklistItem(ExitBB, false));
+          }
+
+          continue;
+        }
+
+        bool IsExitBlock = std::binary_search(ExitBlocks.begin(),
+                                              ExitBlocks.end(), SuccBB);
+        if (IsExitBlock)
+          continue;
+
+        VisitStack.push_back(WorklistItem(SuccBB, false));
+      }
+    }
+
+    // Place the list of instructions to simplify on the next loop iteration
+    // into ToSimplify.
+    std::swap(ToSimplify, Next);
+    Next->clear();
+
+    Changed |= LocalChanged;
+  } while (LocalChanged);
+
+  return Changed;
+}