Fix up instruction classes for Thumb2 RSB instructions to be consistent with

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

diff --git a/lib/CodeGen/CodePlacementOpt.cpp b/lib/CodeGen/CodePlacementOpt.cpp
index cbf5b891f8b9276074fab80ecc32f6208f0b269f..3ff2a046d233683fc95cebdaa3797e52b4d6e861 100644 (file)
--- a/lib/CodeGen/CodePlacementOpt.cpp
+++ b/lib/CodeGen/CodePlacementOpt.cpp
@@ -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().isEHLabel())
-    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;