Make makeLoopInvariant report whether it made any changes or not,

and use this to simplify more code.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75722 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 28 insertions, 56 deletions

diff --git a/include/llvm/Analysis/LoopInfo.h b/include/llvm/Analysis/LoopInfo.h
index 90afc01..de9a30d 100644
--- a/include/llvm/Analysis/LoopInfo.h
+++ b/include/llvm/Analysis/LoopInfo.h
@@ -490,7 +490,8 @@ public:
   /// If InsertPt is specified, it is the point to hoist instructions to.
   /// If null, the terminator of the loop preheader is used.
   ///
-  bool makeLoopInvariant(Value *V, Instruction *InsertPt = 0) const;
+  bool makeLoopInvariant(Value *V, bool &Changed,
+                         Instruction *InsertPt = 0) const;
 
   /// makeLoopInvariant - If the given instruction is inside of the
   /// loop and it can be hoisted, do so to make it trivially loop-invariant.
@@ -501,7 +502,8 @@ public:
   /// If InsertPt is specified, it is the point to hoist instructions to.
   /// If null, the terminator of the loop preheader is used.
   ///
-  bool makeLoopInvariant(Instruction *I, Instruction *InsertPt = 0) const;
+  bool makeLoopInvariant(Instruction *I, bool &Changed,
+                         Instruction *InsertPt = 0) const;
 
   /// getCanonicalInductionVariable - Check to see if the loop has a canonical
   /// induction variable: an integer recurrence that starts at 0 and increments
diff --git a/lib/Analysis/LoopInfo.cpp b/lib/Analysis/LoopInfo.cpp
index fb8027c..63de1aa 100644
--- a/lib/Analysis/LoopInfo.cpp
+++ b/lib/Analysis/LoopInfo.cpp
@@ -58,9 +58,10 @@ bool Loop::isLoopInvariant(Instruction *I) const {
 /// If InsertPt is specified, it is the point to hoist instructions to.
 /// If null, the terminator of the loop preheader is used.
 ///
-bool Loop::makeLoopInvariant(Value *V, Instruction *InsertPt) const {
+bool Loop::makeLoopInvariant(Value *V, bool &Changed,
+                             Instruction *InsertPt) const {
   if (Instruction *I = dyn_cast<Instruction>(V))
-    return makeLoopInvariant(I);
+    return makeLoopInvariant(I, Changed, InsertPt);
   return true;  // All non-instructions are loop-invariant.
 }
 
@@ -73,7 +74,8 @@ bool Loop::makeLoopInvariant(Value *V, Instruction *InsertPt) const {
 /// If InsertPt is specified, it is the point to hoist instructions to.
 /// If null, the terminator of the loop preheader is used.
 ///
-bool Loop::makeLoopInvariant(Instruction *I, Instruction *InsertPt) const {
+bool Loop::makeLoopInvariant(Instruction *I, bool &Changed,
+                             Instruction *InsertPt) const {
   // Test if the value is already loop-invariant.
   if (isLoopInvariant(I))
     return true;
@@ -96,10 +98,11 @@ bool Loop::makeLoopInvariant(Instruction *I, Instruction *InsertPt) const {
   }
   // Don't hoist instructions with loop-variant operands.
   for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
-    if (!makeLoopInvariant(I->getOperand(i), InsertPt))
+    if (!makeLoopInvariant(I->getOperand(i), Changed, InsertPt))
       return false;
   // Hoist.
   I->moveBefore(InsertPt);
+  Changed = true;
   return true;
 }
 
diff --git a/lib/Transforms/Scalar/LoopDeletion.cpp b/lib/Transforms/Scalar/LoopDeletion.cpp
index 38d0b39..525d03f 100644
--- a/lib/Transforms/Scalar/LoopDeletion.cpp
+++ b/lib/Transforms/Scalar/LoopDeletion.cpp
@@ -38,9 +38,9 @@ namespace {
     bool SingleDominatingExit(Loop* L,
                               SmallVector<BasicBlock*, 4>& exitingBlocks);
     bool IsLoopDead(Loop* L, SmallVector<BasicBlock*, 4>& exitingBlocks,
-                    SmallVector<BasicBlock*, 4>& exitBlocks);
-    bool IsLoopInvariantInst(Instruction *I, Loop* L);
-    
+                    SmallVector<BasicBlock*, 4>& exitBlocks,
+                    bool &Changed, BasicBlock *Preheader);
+
     virtual void getAnalysisUsage(AnalysisUsage& AU) const {
       AU.addRequired<ScalarEvolution>();
       AU.addRequired<DominatorTree>();
@@ -84,32 +84,13 @@ bool LoopDeletion::SingleDominatingExit(Loop* L,
   return DT.dominates(exitingBlocks[0], latch);
 }
 
-/// IsLoopInvariantInst - Checks if an instruction is invariant with respect to
-/// a loop, which is defined as being true if all of its operands are defined
-/// outside of the loop.  These instructions can be hoisted out of the loop
-/// if their results are needed.  This could be made more aggressive by
-/// recursively checking the operands for invariance, but it's not clear that
-/// it's worth it.
-bool LoopDeletion::IsLoopInvariantInst(Instruction *I, Loop* L)  {
-  // PHI nodes are not loop invariant if defined in  the loop.
-  if (isa<PHINode>(I) && L->contains(I->getParent()))
-    return false;
-    
-  // The instruction is loop invariant if all of its operands are loop-invariant
-  for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
-    if (!L->isLoopInvariant(I->getOperand(i)))
-      return false;
-  
-  // If we got this far, the instruction is loop invariant!
-  return true;
-}
-
 /// IsLoopDead - Determined if a loop is dead.  This assumes that we've already
 /// checked for unique exit and exiting blocks, and that the code is in LCSSA
 /// form.
 bool LoopDeletion::IsLoopDead(Loop* L,
                               SmallVector<BasicBlock*, 4>& exitingBlocks,
-                              SmallVector<BasicBlock*, 4>& exitBlocks) {
+                              SmallVector<BasicBlock*, 4>& exitBlocks,
+                              bool &Changed, BasicBlock *Preheader) {
   BasicBlock* exitingBlock = exitingBlocks[0];
   BasicBlock* exitBlock = exitBlocks[0];
   
@@ -122,7 +103,7 @@ bool LoopDeletion::IsLoopDead(Loop* L,
   while (PHINode* P = dyn_cast<PHINode>(BI)) {
     Value* incoming = P->getIncomingValueForBlock(exitingBlock);
     if (Instruction* I = dyn_cast<Instruction>(incoming))
-      if (!IsLoopInvariantInst(I, L))
+      if (!L->makeLoopInvariant(I, Changed, Preheader->getTerminator()))
         return false;
       
     BI++;
@@ -181,15 +162,16 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
     return false;
   
   // Finally, we have to check that the loop really is dead.
-  if (!IsLoopDead(L, exitingBlocks, exitBlocks))
-    return false;
+  bool Changed = false;
+  if (!IsLoopDead(L, exitingBlocks, exitBlocks, Changed, preheader))
+    return Changed;
   
   // Don't remove loops for which we can't solve the trip count.
   // They could be infinite, in which case we'd be changing program behavior.
   ScalarEvolution& SE = getAnalysis<ScalarEvolution>();
   const SCEV *S = SE.getBackedgeTakenCount(L);
   if (isa<SCEVCouldNotCompute>(S))
-    return false;
+    return Changed;
   
   // Now that we know the removal is safe, remove the loop by changing the
   // branch from the preheader to go to the single exit block.  
@@ -205,17 +187,6 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
   // to determine what it needs to clean up.
   SE.forgetLoopBackedgeTakenCount(L);
 
-  // Move simple loop-invariant expressions out of the loop, since they
-  // might be needed by the exit phis.
-  for (Loop::block_iterator LI = L->block_begin(), LE = L->block_end();
-       LI != LE; ++LI)
-    for (BasicBlock::iterator BI = (*LI)->begin(), BE = (*LI)->end();
-         BI != BE; ) {
-      Instruction* I = BI++;
-      if (!I->use_empty() && IsLoopInvariantInst(I, L))
-        I->moveBefore(preheader->getTerminator());
-    }
-  
   // Connect the preheader directly to the exit block.
   TerminatorInst* TI = preheader->getTerminator();
   TI->replaceUsesOfWith(L->getHeader(), exitBlock);
@@ -273,8 +244,9 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
   // The last step is to inform the loop pass manager that we've
   // eliminated this loop.
   LPM.deleteLoopFromQueue(L);
+  Changed = true;
   
   NumDeleted++;
   
-  return true;
+  return Changed;
 }
diff --git a/lib/Transforms/Scalar/LoopUnswitch.cpp b/lib/Transforms/Scalar/LoopUnswitch.cpp
index f5061b5..daf1841 100644
--- a/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -168,13 +168,10 @@ static Value *FindLIVLoopCondition(Value *Cond, Loop *L, bool &Changed) {
   if (isa<Constant>(Cond)) return 0;
 
   // TODO: Handle: br (VARIANT|INVARIANT).
-  if (L->isLoopInvariant(Cond)) return Cond;
 
   // Hoist simple values out.
-  if (L->makeLoopInvariant(Cond)) {
-    Changed = true;
+  if (L->makeLoopInvariant(Cond, Changed))
     return Cond;
-  }
 
   if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Cond))
     if (BO->getOpcode() == Instruction::And ||
diff --git a/lib/Transforms/Utils/LoopSimplify.cpp b/lib/Transforms/Utils/LoopSimplify.cpp
index cfdfcb0..81fa4f9 100644
--- a/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/lib/Transforms/Utils/LoopSimplify.cpp
@@ -93,7 +93,7 @@ namespace {
     BasicBlock *RewriteLoopExitBlock(Loop *L, BasicBlock *Exit);
     BasicBlock *InsertPreheaderForLoop(Loop *L);
     Loop *SeparateNestedLoop(Loop *L);
-    void InsertUniqueBackedgeBlock(Loop *L);
+    void InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader);
     void PlaceSplitBlockCarefully(BasicBlock *NewBB,
                                   SmallVectorImpl<BasicBlock*> &SplitPreds,
                                   Loop *L);
@@ -244,7 +244,7 @@ ReprocessLoop:
     // If we either couldn't, or didn't want to, identify nesting of the loops,
     // insert a new block that all backedges target, then make it jump to the
     // loop header.
-    InsertUniqueBackedgeBlock(L);
+    InsertUniqueBackedgeBlock(L, Preheader);
     NumInserted++;
     Changed = true;
   }
@@ -288,9 +288,8 @@ ReprocessLoop:
         Instruction *Inst = I++;
         if (Inst == CI)
           continue;
-        if (!L->makeLoopInvariant(Inst, Preheader->getTerminator())) {
+        if (!L->makeLoopInvariant(Inst, Changed, Preheader->getTerminator())) {
           AllInvariant = false;
-          Changed = true;
           break;
         }
       }
@@ -574,11 +573,10 @@ Loop *LoopSimplify::SeparateNestedLoop(Loop *L) {
 /// backedges to target a new basic block and have that block branch to the loop
 /// header.  This ensures that loops have exactly one backedge.
 ///
-void LoopSimplify::InsertUniqueBackedgeBlock(Loop *L) {
+void LoopSimplify::InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader) {
   assert(L->getNumBackEdges() > 1 && "Must have > 1 backedge!");
 
   // Get information about the loop
-  BasicBlock *Preheader = L->getLoopPreheader();
   BasicBlock *Header = L->getHeader();
   Function *F = Header->getParent();