Reapply r110396, with fixes to appease the Linux buildbot gods.

[oota-llvm.git] / lib / CodeGen / CodePlacementOpt.cpp

diff --git a/lib/CodeGen/CodePlacementOpt.cpp b/lib/CodeGen/CodePlacementOpt.cpp
index 126700b7fe5b0846f0e7b398a9a923690db69c81..91a9536e7757c250634194021496e691f4937fb5 100644 (file)
--- a/lib/CodeGen/CodePlacementOpt.cpp
+++ b/lib/CodeGen/CodePlacementOpt.cpp
@@ -36,7 +36,7 @@ namespace {
 
   public:
     static char ID;
-    CodePlacementOpt() : MachineFunctionPass(&ID) {}
+    CodePlacementOpt() : MachineFunctionPass(ID) {}
 
     virtual bool runOnMachineFunction(MachineFunction &MF);
     virtual const char *getPassName() const {
@@ -102,22 +102,23 @@ bool CodePlacementOpt::HasAnalyzableTerminator(MachineBasicBlock *MBB) {
   // Conservatively ignore EH landing pads.
   if (MBB->isLandingPad()) return false;
 
-  // Ignore blocks which look like they might have EH-related control flow.
-  // At the time of this writing, there are blocks which AnalyzeBranch
-  // thinks end in single uncoditional branches, yet which have two CFG
-  // successors. Code in this file is not prepared to reason about such things.
-  if (!MBB->empty() && MBB->back().getOpcode() == TargetInstrInfo::EH_LABEL)
-    return false;
-
   // Aggressively handle return blocks and similar constructs.
   if (MBB->succ_empty()) return true;
 
   // Ask the target's AnalyzeBranch if it can handle this block.
   MachineBasicBlock *TBB = 0, *FBB = 0;
   SmallVector<MachineOperand, 4> Cond;
-  // Make the the terminator is understood.
+  // Make sure the terminator is understood.
   if (TII->AnalyzeBranch(*MBB, TBB, FBB, Cond))
     return false;
+   // Ignore blocks which look like they might have EH-related control flow.
+   // AnalyzeBranch thinks it knows how to analyze such things, but it doesn't
+   // recognize the possibility of a control transfer through an unwind.
+   // Such blocks contain EH_LABEL instructions, however they may be in the
+   // middle of the block. Instead of searching for them, just check to see
+   // if the CFG disagrees with AnalyzeBranch.
+  if (1u + !Cond.empty() != MBB->succ_size())
+    return false;
   // Make sure we have the option of reversing the condition.
   if (!Cond.empty() && TII->ReverseBranchCondition(Cond))
     return false;
@@ -177,6 +178,8 @@ bool CodePlacementOpt::EliminateUnconditionalJumpsToTop(MachineFunction &MF,
         continue;
 
       // Move the block.
+      DEBUG(dbgs() << "CGP: Moving blocks starting at BB#" << Pred->getNumber()
+                   << " to top of loop.\n");
       Changed = true;
 
       // Move it and all the blocks that can reach it via fallthrough edges
@@ -296,6 +299,8 @@ bool CodePlacementOpt::MoveDiscontiguousLoopBlocks(MachineFunction &MF,
         continue;
 
       // Move the block.
+      DEBUG(dbgs() << "CGP: Moving blocks starting at BB#" << BB->getNumber()
+                   << " to be contiguous with loop.\n");
       Changed = true;
 
       // Process this block and all loop blocks contiguous with it, to keep