Simplify this code: don't call AnalyzeBranch before doing simpler checks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90633 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index 5ef25ca4eede40eefacf10d4c5ca5e5770ac146a..de358fa31f5ffd77fcf205d80e3e59b5f8218170 100644 (file)
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -363,11 +363,6 @@ bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
 }
 
 bool MachineBasicBlock::canFallThrough() {
-  MachineBasicBlock *TBB = 0, *FBB = 0;
-  SmallVector<MachineOperand, 4> Cond;
-  const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
-  bool BranchUnAnalyzable = TII->AnalyzeBranch(*this, TBB, FBB, Cond, true);
-
   MachineFunction::iterator Fallthrough = this;
   ++Fallthrough;
   // If FallthroughBlock is off the end of the function, it can't fall through.
@@ -378,16 +373,21 @@ bool MachineBasicBlock::canFallThrough() {
   if (!isSuccessor(Fallthrough))
     return false;
 
-  // If we couldn't analyze the branch, examine the last instruction.
-  // If the block doesn't end in a known control barrier, assume fallthrough
-  // is possible. The isPredicable check is needed because this code can be
-  // called during IfConversion, where an instruction which is normally a
-  // Barrier is predicated and thus no longer an actual control barrier. This
-  // is over-conservative though, because if an instruction isn't actually
-  // predicated we could still treat it like a barrier.
-  if (BranchUnAnalyzable)
+  // Analyze the branches, if any, at the end of the block.
+  MachineBasicBlock *TBB = 0, *FBB = 0;
+  SmallVector<MachineOperand, 4> Cond;
+  const TargetInstrInfo *TII = getParent()->getTarget().getInstrInfo();
+  if (TII->AnalyzeBranch(*this, TBB, FBB, Cond, true)) {
+    // If we couldn't analyze the branch, examine the last instruction.
+    // If the block doesn't end in a known control barrier, assume fallthrough
+    // is possible. The isPredicable check is needed because this code can be
+    // called during IfConversion, where an instruction which is normally a
+    // Barrier is predicated and thus no longer an actual control barrier. This
+    // is over-conservative though, because if an instruction isn't actually
+    // predicated we could still treat it like a barrier.
     return empty() || !back().getDesc().isBarrier() ||
            back().getDesc().isPredicable();
+  }
 
   // If there is no branch, control always falls through.
   if (TBB == 0) return true;