[llvm-commits] [llvm] r122791 - /llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp

[Cameron Zwarich]

Author: zwarich
Date: Mon Jan  3 18:12:46 2011
New Revision: 122791

URL: http://llvm.org/viewvc/llvm-project?rev=122791&view=rev
Log:
Address most of Duncan's review comments. Also, make LoopInstSimplify a simple
FunctionPass. It probably doesn't have a reason to be a LoopPass, as it will
probably drop the simple fixed point and either use RPO iteration or Duncan's
approach in instsimplify of only revisiting instructions that have changed.

The next step is to preserve LoopSimplify. This looks like it won't be too hard,
although the pass manager doesn't actually seem to respect when non-loop passes
claim to preserve LCSSA or LoopSimplify. This will have to be fixed.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp?rev=122791&r1=122790&r2=122791&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LoopInstSimplify.cpp Mon Jan  3 18:12:46 2011
@@ -12,9 +12,11 @@
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "loop-instsimplify"
-#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Function.h"
+#include "llvm/Pass.h"
 #include "llvm/Analysis/Dominators.h"
 #include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/Local.h"
@@ -24,19 +26,17 @@
 STATISTIC(NumSimplified, "Number of redundant instructions simplified");
 
 namespace {
-  class LoopInstSimplify : public LoopPass {
+  class LoopInstSimplify : public FunctionPass {
   public:
     static char ID; // Pass ID, replacement for typeid
-    LoopInstSimplify() : LoopPass(ID) {
+    LoopInstSimplify() : FunctionPass(ID) {
       initializeLoopInstSimplifyPass(*PassRegistry::getPassRegistry());
     }
 
-    bool runOnLoop(Loop*, LPPassManager&);
+    bool runOnFunction(Function&);
 
     virtual void getAnalysisUsage(AnalysisUsage& AU) const {
       AU.setPreservesCFG();
-      AU.addRequired<DominatorTree>();
-      AU.addPreserved<DominatorTree>();
       AU.addRequired<LoopInfo>();
       AU.addPreserved<LoopInfo>();
       AU.addPreservedID(LCSSAID);
@@ -57,9 +57,9 @@
   return new LoopInstSimplify();
 }
 
-bool LoopInstSimplify::runOnLoop(Loop* L, LPPassManager& LPM) {
-  DominatorTree* DT = &getAnalysis<DominatorTree>();
-  const LoopInfo* LI = &getAnalysis<LoopInfo>();
+bool LoopInstSimplify::runOnFunction(Function& F) {
+  DominatorTree* DT = getAnalysisIfAvailable<DominatorTree>();
+  LoopInfo* LI = &getAnalysis<LoopInfo>();
   const TargetData* TD = getAnalysisIfAvailable<TargetData>();
 
   bool Changed = false;
@@ -67,24 +67,14 @@
   do {
     LocalChanged = false;
 
-    SmallPtrSet<BasicBlock*, 32> Visited;
-    SmallVector<BasicBlock*, 32> VisitStack;
-
-    VisitStack.push_back(L->getHeader());
-
-    while (!VisitStack.empty()) {
-      BasicBlock* BB = VisitStack.back();
-      VisitStack.pop_back();
-
-      if (Visited.count(BB))
-        continue;
-      Visited.insert(BB);
-
-      for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
+    for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
+         DE = df_end(&F.getEntryBlock()); DI != DE; ++DI)
+      for (BasicBlock::iterator BI = DI->begin(), BE = DI->end(); BI != BE;) {
         Instruction* I = BI++;
         // Don't bother simplifying unused instructions.
         if (!I->use_empty()) {
-          if (Value* V = SimplifyInstruction(I, TD, DT)) {
+          Value* V = SimplifyInstruction(I, TD, DT);
+          if (V && LI->replacementPreservesLCSSAForm(I, V)) {
             I->replaceAllUsesWith(V);
             LocalChanged = true;
             ++NumSimplified;
@@ -92,21 +82,9 @@
         }
         LocalChanged |= RecursivelyDeleteTriviallyDeadInstructions(I);
       }
-      Changed |= LocalChanged;
 
-      DomTreeNode* Node = DT->getNode(BB);
-      const std::vector<DomTreeNode*>& Children = Node->getChildren();
-      for (unsigned i = 0; i < Children.size(); ++i) {
-        // Only visit children that are in the same loop.
-        BasicBlock* ChildBB = Children[i]->getBlock();
-        if (!Visited.count(ChildBB) && LI->getLoopFor(ChildBB) == L)
-          VisitStack.push_back(ChildBB);
-      }
-    }
+    Changed |= LocalChanged;
   } while (LocalChanged);
 
-  // Nothing that SimplifyInstruction() does should invalidate LCSSA form.
-  assert(L->isLCSSAForm(*DT));
-
   return Changed;
 }