Remove trailing whitespace from SelectionDAG/*.cpp

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

diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp
index 774df81b4d578397f4473f77a5cc623d0b2b5842..4b0f7f38fcc9ecef0426a370936d92e3dd659092 100644 (file)
--- a/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/lib/CodeGen/MachineBlockPlacement.cpp
@@ -991,6 +991,28 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) {
     Cond.clear();
     MachineBasicBlock *TBB = 0, *FBB = 0; // For AnalyzeBranch.
     if (!TII->AnalyzeBranch(*PrevBB, TBB, FBB, Cond)) {
+      // The "PrevBB" is not yet updated to reflect current code layout, so,
+      //   o. it may fall-through to a block without explict "goto" instruction
+      //      before layout, and no longer fall-through it after layout; or 
+      //   o. just opposite.
+      // 
+      // AnalyzeBranch() may return erroneous value for FBB when these two
+      // situations take place. For the first scenario FBB is mistakenly set
+      // NULL; for the 2nd scenario, the FBB, which is expected to be NULL,
+      // is mistakenly pointing to "*BI".
+      //
+      bool needUpdateBr = true;
+      if (!Cond.empty() && (!FBB || FBB == *BI)) {
+        PrevBB->updateTerminator();
+        needUpdateBr = false;
+        Cond.clear();
+        TBB = FBB = 0;
+        if (TII->AnalyzeBranch(*PrevBB, TBB, FBB, Cond)) {
+          // FIXME: This should never take place.
+          TBB = FBB = 0;
+        }
+      }
+
       // If PrevBB has a two-way branch, try to re-order the branches
       // such that we branch to the successor with higher weight first.
       if (TBB && !Cond.empty() && FBB &&
@@ -1003,8 +1025,10 @@ void MachineBlockPlacement::buildCFGChains(MachineFunction &F) {
         DebugLoc dl;  // FIXME: this is nowhere
         TII->RemoveBranch(*PrevBB);
         TII->InsertBranch(*PrevBB, FBB, TBB, Cond, dl);
+        needUpdateBr = true;
       }
-      PrevBB->updateTerminator();
+      if (needUpdateBr)
+        PrevBB->updateTerminator();
     }
   }
 
@@ -1089,19 +1113,17 @@ bool MachineBlockPlacement::runOnMachineFunction(MachineFunction &F) {
   TLI = F.getTarget().getTargetLowering();
   assert(BlockToChain.empty());
 
-  if (AlignAllBlock) {
-    // Align all of the blocks in the function to a specific alignment.
-    for (MachineFunction::iterator FI = F.begin(), FE = F.end();
-         FI != FE; ++FI)
-      FI->setAlignment(AlignAllBlock);
-    return true;
-  }
-
   buildCFGChains(F);
 
   BlockToChain.clear();
   ChainAllocator.DestroyAll();
 
+  if (AlignAllBlock)
+    // Align all of the blocks in the function to a specific alignment.
+    for (MachineFunction::iterator FI = F.begin(), FE = F.end();
+         FI != FE; ++FI)
+      FI->setAlignment(AlignAllBlock);
+
   // We always return true as we have no way to track whether the final order
   // differs from the original order.
   return true;