[llvm-commits] CVS: llvm/lib/Analysis/LoopInfo.cpp ScalarEvolution.cpp

[Chris Lattner]

Changes in directory llvm/lib/Analysis:

LoopInfo.cpp updated: 1.51 -> 1.52
ScalarEvolution.cpp updated: 1.14 -> 1.15

---
Log message:

Change the ExitBlocks list from being explicitly contained in the Loop
structure to being dynamically computed on demand.  This makes updating
loop information MUCH easier.


---
Diffs of the changes:  (+20 -46)

Index: llvm/lib/Analysis/LoopInfo.cpp
diff -u llvm/lib/Analysis/LoopInfo.cpp:1.51 llvm/lib/Analysis/LoopInfo.cpp:1.52
--- llvm/lib/Analysis/LoopInfo.cpp:1.51	Sun Apr 18 01:54:48 2004
+++ llvm/lib/Analysis/LoopInfo.cpp	Sun Apr 18 17:13:35 2004
@@ -63,14 +63,6 @@
     if (i) OS << ",";
     WriteAsOperand(OS, getBlocks()[i], false);
   }
-  if (!ExitBlocks.empty()) {
-    OS << "\tExitBlocks: ";
-    for (unsigned i = 0; i < getExitBlocks().size(); ++i) {
-      if (i) OS << ",";
-      WriteAsOperand(OS, getExitBlocks()[i], false);
-    }
-  }
-
   OS << "\n";
 
   for (iterator I = begin(), E = end(); I != E; ++I)
@@ -248,14 +240,6 @@
     }
   }
 
-  // Now that we know all of the blocks that make up this loop, see if there are
-  // any branches to outside of the loop... building the ExitBlocks list.
-  for (std::vector<BasicBlock*>::iterator BI = L->Blocks.begin(),
-         BE = L->Blocks.end(); BI != BE; ++BI)
-    for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I)
-      if (!L->contains(*I))               // Not in current loop?
-        L->ExitBlocks.push_back(*I);      // It must be an exit block...
-
   return L;
 }
 
@@ -344,6 +328,18 @@
 // APIs for simple analysis of the loop.
 //
 
+/// getExitBlocks - Return all of the successor blocks of this loop.  These
+/// are the blocks _outside of the current loop_ which are branched to.
+///
+void Loop::getExitBlocks(std::vector<BasicBlock*> &Blocks) const {
+  for (std::vector<BasicBlock*>::const_iterator BI = Blocks.begin(),
+         BE = Blocks.end(); BI != BE; ++BI)
+    for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I)
+      if (!contains(*I))               // Not in current loop?
+        Blocks.push_back(*I);          // It must be an exit block...
+}
+
+
 /// getLoopPreheader - If there is a preheader for this loop, return it.  A
 /// loop has a preheader if there is only one edge to the header of the loop
 /// from outside of the loop.  If this is the case, the block branching to the
@@ -481,22 +477,6 @@
   }
 }
 
-/// changeExitBlock - This method is used to update loop information.  All
-/// instances of the specified Old basic block are removed from the exit list
-/// and replaced with New.
-///
-void Loop::changeExitBlock(BasicBlock *Old, BasicBlock *New) {
-  assert(Old != New && "Cannot changeExitBlock to the same thing!");
-  assert(Old && New && "Cannot changeExitBlock to or from a null node!");
-  assert(hasExitBlock(Old) && "Old exit block not found!");
-  std::vector<BasicBlock*>::iterator
-    I = std::find(ExitBlocks.begin(), ExitBlocks.end(), Old);
-  while (I != ExitBlocks.end()) {
-    *I = New;
-    I = std::find(I+1, ExitBlocks.end(), Old);
-  }
-}
-
 /// replaceChildLoopWith - This is used when splitting loops up.  It replaces
 /// the OldChild entry in our children list with NewChild, and updates the
 /// parent pointers of the two loops as appropriate.
@@ -550,15 +530,4 @@
 /// does not update the mapping in the LoopInfo class.
 void Loop::removeBlockFromLoop(BasicBlock *BB) {
   RemoveFromVector(Blocks, BB);
-
-  // If this block branched out of this loop, remove any exit blocks entries due
-  // to it.
-  for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
-    if (!contains(*SI) && *SI != BB)
-      RemoveFromVector(ExitBlocks, *SI);
-
-  // If any blocks in this loop branch to BB, add it to the exit blocks set.
-  for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
-    if (contains(*PI))
-      ExitBlocks.push_back(BB);
 }


Index: llvm/lib/Analysis/ScalarEvolution.cpp
diff -u llvm/lib/Analysis/ScalarEvolution.cpp:1.14 llvm/lib/Analysis/ScalarEvolution.cpp:1.15
--- llvm/lib/Analysis/ScalarEvolution.cpp:1.14	Sat Apr 17 17:58:41 2004
+++ llvm/lib/Analysis/ScalarEvolution.cpp	Sun Apr 18 17:13:35 2004
@@ -1452,11 +1452,13 @@
 /// will iterate.
 SCEVHandle ScalarEvolutionsImpl::ComputeIterationCount(const Loop *L) {
   // If the loop has a non-one exit block count, we can't analyze it.
-  if (L->getExitBlocks().size() != 1) return UnknownValue;
+  std::vector<BasicBlock*> ExitBlocks;
+  L->getExitBlocks(ExitBlocks);
+  if (ExitBlocks.size() != 1) return UnknownValue;
 
   // Okay, there is one exit block.  Try to find the condition that causes the
   // loop to be exited.
-  BasicBlock *ExitBlock = L->getExitBlocks()[0];
+  BasicBlock *ExitBlock = ExitBlocks[0];
 
   BasicBlock *ExitingBlock = 0;
   for (pred_iterator PI = pred_begin(ExitBlock), E = pred_end(ExitBlock);
@@ -2293,7 +2295,10 @@
     PrintLoopInfo(OS, SE, *I);
   
   std::cerr << "Loop " << L->getHeader()->getName() << ": ";
-  if (L->getExitBlocks().size() != 1)
+
+  std::vector<BasicBlock*> ExitBlocks;
+  L->getExitBlocks(ExitBlocks);
+  if (ExitBlocks.size() != 1)
     std::cerr << "<multiple exits> ";
 
   if (SE->hasLoopInvariantIterationCount(L)) {