Check in LLVM r95781.
diff --git a/lib/Analysis/LiveValues.cpp b/lib/Analysis/LiveValues.cpp
new file mode 100644
index 0000000..1b91d93
--- /dev/null
+++ b/lib/Analysis/LiveValues.cpp
@@ -0,0 +1,193 @@
+//===- LiveValues.cpp - Liveness information for LLVM IR Values. ----------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the implementation for the LLVM IR Value liveness
+// analysis pass.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/LiveValues.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/LoopInfo.h"
+using namespace llvm;
+
+namespace llvm {
+ FunctionPass *createLiveValuesPass() { return new LiveValues(); }
+}
+
+char LiveValues::ID = 0;
+static RegisterPass<LiveValues>
+X("live-values", "Value Liveness Analysis", false, true);
+
+LiveValues::LiveValues() : FunctionPass(&ID) {}
+
+void LiveValues::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<DominatorTree>();
+ AU.addRequired<LoopInfo>();
+ AU.setPreservesAll();
+}
+
+bool LiveValues::runOnFunction(Function &F) {
+ DT = &getAnalysis<DominatorTree>();
+ LI = &getAnalysis<LoopInfo>();
+
+ // This pass' values are computed lazily, so there's nothing to do here.
+
+ return false;
+}
+
+void LiveValues::releaseMemory() {
+ Memos.clear();
+}
+
+/// isUsedInBlock - Test if the given value is used in the given block.
+///
+bool LiveValues::isUsedInBlock(const Value *V, const BasicBlock *BB) {
+ Memo &M = getMemo(V);
+ return M.Used.count(BB);
+}
+
+/// isLiveThroughBlock - Test if the given value is known to be
+/// live-through the given block, meaning that the block is properly
+/// dominated by the value's definition, and there exists a block
+/// reachable from it that contains a use. This uses a conservative
+/// approximation that errs on the side of returning false.
+///
+bool LiveValues::isLiveThroughBlock(const Value *V,
+ const BasicBlock *BB) {
+ Memo &M = getMemo(V);
+ return M.LiveThrough.count(BB);
+}
+
+/// isKilledInBlock - Test if the given value is known to be killed in
+/// the given block, meaning that the block contains a use of the value,
+/// and no blocks reachable from the block contain a use. This uses a
+/// conservative approximation that errs on the side of returning false.
+///
+bool LiveValues::isKilledInBlock(const Value *V, const BasicBlock *BB) {
+ Memo &M = getMemo(V);
+ return M.Killed.count(BB);
+}
+
+/// getMemo - Retrieve an existing Memo for the given value if one
+/// is available, otherwise compute a new one.
+///
+LiveValues::Memo &LiveValues::getMemo(const Value *V) {
+ DenseMap<const Value *, Memo>::iterator I = Memos.find(V);
+ if (I != Memos.end())
+ return I->second;
+ return compute(V);
+}
+
+/// getImmediateDominator - A handy utility for the specific DominatorTree
+/// query that we need here.
+///
+static const BasicBlock *getImmediateDominator(const BasicBlock *BB,
+ const DominatorTree *DT) {
+ DomTreeNode *Node = DT->getNode(const_cast<BasicBlock *>(BB))->getIDom();
+ return Node ? Node->getBlock() : 0;
+}
+
+/// compute - Compute a new Memo for the given value.
+///
+LiveValues::Memo &LiveValues::compute(const Value *V) {
+ Memo &M = Memos[V];
+
+ // Determine the block containing the definition.
+ const BasicBlock *DefBB;
+ // Instructions define values with meaningful live ranges.
+ if (const Instruction *I = dyn_cast<Instruction>(V))
+ DefBB = I->getParent();
+ // Arguments can be analyzed as values defined in the entry block.
+ else if (const Argument *A = dyn_cast<Argument>(V))
+ DefBB = &A->getParent()->getEntryBlock();
+ // Constants and other things aren't meaningful here, so just
+ // return having computed an empty Memo so that we don't come
+ // here again. The assumption here is that client code won't
+ // be asking about such values very often.
+ else
+ return M;
+
+ // Determine if the value is defined inside a loop. This is used
+ // to track whether the value is ever used outside the loop, so
+ // it'll be set to null if the value is either not defined in a
+ // loop or used outside the loop in which it is defined.
+ const Loop *L = LI->getLoopFor(DefBB);
+
+ // Track whether the value is used anywhere outside of the block
+ // in which it is defined.
+ bool LiveOutOfDefBB = false;
+
+ // Examine each use of the value.
+ for (Value::use_const_iterator I = V->use_begin(), E = V->use_end();
+ I != E; ++I) {
+ const User *U = *I;
+ const BasicBlock *UseBB = cast<Instruction>(U)->getParent();
+
+ // Note the block in which this use occurs.
+ M.Used.insert(UseBB);
+
+ // If the use block doesn't have successors, the value can be
+ // considered killed.
+ if (succ_begin(UseBB) == succ_end(UseBB))
+ M.Killed.insert(UseBB);
+
+ // Observe whether the value is used outside of the loop in which
+ // it is defined. Switch to an enclosing loop if necessary.
+ for (; L; L = L->getParentLoop())
+ if (L->contains(UseBB))
+ break;
+
+ // Search for live-through blocks.
+ const BasicBlock *BB;
+ if (const PHINode *PHI = dyn_cast<PHINode>(U)) {
+ // For PHI nodes, start the search at the incoming block paired with the
+ // incoming value, which must be dominated by the definition.
+ unsigned Num = PHI->getIncomingValueNumForOperand(I.getOperandNo());
+ BB = PHI->getIncomingBlock(Num);
+
+ // A PHI-node use means the value is live-out of it's defining block
+ // even if that block also contains the only use.
+ LiveOutOfDefBB = true;
+ } else {
+ // Otherwise just start the search at the use.
+ BB = UseBB;
+
+ // Note if the use is outside the defining block.
+ LiveOutOfDefBB |= UseBB != DefBB;
+ }
+
+ // Climb the immediate dominator tree from the use to the definition
+ // and mark all intermediate blocks as live-through.
+ for (; BB != DefBB; BB = getImmediateDominator(BB, DT)) {
+ if (BB != UseBB && !M.LiveThrough.insert(BB))
+ break;
+ }
+ }
+
+ // If the value is defined inside a loop and is not live outside
+ // the loop, then each exit block of the loop in which the value
+ // is used is a kill block.
+ if (L) {
+ SmallVector<BasicBlock *, 4> ExitingBlocks;
+ L->getExitingBlocks(ExitingBlocks);
+ for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
+ const BasicBlock *ExitingBlock = ExitingBlocks[i];
+ if (M.Used.count(ExitingBlock))
+ M.Killed.insert(ExitingBlock);
+ }
+ }
+
+ // If the value was never used outside the block in which it was
+ // defined, it's killed in that block.
+ if (!LiveOutOfDefBB)
+ M.Killed.insert(DefBB);
+
+ return M;
+}