AnalyzeBranch doesn't change which successors a bb has, just the order

we try to branch to them.

Before we were creating successor lists with duplicated entries. Fixing that
found a bug in isBlockOnlyReachableByFallthrough that would causes it to
return the wrong answer for

-----------
...
jne foo
jmp bar

foo:
----------

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132882 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 13 insertions, 7 deletions

diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 161afbafb5..1fd724f9ca 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1925,7 +1925,7 @@ isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const {
     return false;
 
   // The predecessor has to be immediately before this block.
-  const MachineBasicBlock *Pred = *PI;
+  MachineBasicBlock *Pred = *PI;
 
   if (!Pred->isLayoutSuccessor(MBB))
     return false;
@@ -1934,9 +1934,16 @@ isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const {
   if (Pred->empty())
     return true;
 
-  // Otherwise, check the last instruction.
-  const MachineInstr &LastInst = Pred->back();
-  return !LastInst.getDesc().isBarrier();
+  // Otherwise, ask the backend.
+  const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
+  MachineBasicBlock *PredTBB = NULL, *PredFBB = NULL;
+  SmallVector<MachineOperand, 4> PredCond;
+  if (TII->AnalyzeBranch(*Pred, PredTBB, PredFBB, PredCond))
+    return false;
+
+  if (PredCond.empty())
+    return true;
+  return !PredFBB || PredFBB == MBB;
 }
 
 
diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index e2016eb2d6..b3237d5971 100644
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -1789,7 +1789,6 @@ bool X86InstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
           .addMBB(UnCondBrIter->getOperand(0).getMBB());
         BuildMI(MBB, UnCondBrIter, MBB.findDebugLoc(I), get(X86::JMP_4))
           .addMBB(TargetBB);
-        MBB.addSuccessor(TargetBB);
 
         OldInst->eraseFromParent();
         UnCondBrIter->eraseFromParent();
diff --git a/test/CodeGen/Thumb2/machine-licm.ll b/test/CodeGen/Thumb2/machine-licm.ll
index ee054a165a..2468aa6cab 100644
--- a/test/CodeGen/Thumb2/machine-licm.ll
+++ b/test/CodeGen/Thumb2/machine-licm.ll
@@ -13,7 +13,7 @@ entry:
   br i1 %0, label %return, label %bb.nph
 
 bb.nph:                                           ; preds = %entry
-; CHECK: BB#1
+; CHECK: LBB0_1:
 ; CHECK: movw r[[R2:[0-9]+]], :lower16:L_GV$non_lazy_ptr
 ; CHECK: movt r[[R2]], :upper16:L_GV$non_lazy_ptr
 ; CHECK: ldr{{(.w)?}} r[[R2b:[0-9]+]], [r[[R2]]
@@ -21,7 +21,7 @@ bb.nph:                                           ; preds = %entry
 ; CHECK: LBB0_2
 ; CHECK-NOT: LCPI0_0:
 
-; PIC: BB#1
+; PIC: LBB0_1:
 ; PIC: movw r[[R2:[0-9]+]], :lower16:(L_GV$non_lazy_ptr-(LPC0_0+4))
 ; PIC: movt r[[R2]], :upper16:(L_GV$non_lazy_ptr-(LPC0_0+4))
 ; PIC: add r[[R2]], pc