1 files changed, 44 insertions, 13 deletions

diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index 3869f976854d..06112723497b 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -23,6 +23,7 @@
 #include "llvm/CodeGen/SlotIndexes.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/ModuleSlotTracker.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
@@ -148,8 +149,11 @@ MachineBasicBlock::iterator MachineBasicBlock::getFirstNonPHI() {
 
 MachineBasicBlock::iterator
 MachineBasicBlock::SkipPHIsAndLabels(MachineBasicBlock::iterator I) {
+  const TargetInstrInfo *TII = getParent()->getSubtarget().getInstrInfo();
+
   iterator E = end();
-  while (I != E && (I->isPHI() || I->isPosition()))
+  while (I != E && (I->isPHI() || I->isPosition() ||
+                    TII->isBasicBlockPrologue(*I)))
     ++I;
   // FIXME: This needs to change if we wish to bundle labels
   // inside the bundle.
@@ -160,8 +164,11 @@ MachineBasicBlock::SkipPHIsAndLabels(MachineBasicBlock::iterator I) {
 
 MachineBasicBlock::iterator
 MachineBasicBlock::SkipPHIsLabelsAndDebug(MachineBasicBlock::iterator I) {
+  const TargetInstrInfo *TII = getParent()->getSubtarget().getInstrInfo();
+
   iterator E = end();
-  while (I != E && (I->isPHI() || I->isPosition() || I->isDebugValue()))
+  while (I != E && (I->isPHI() || I->isPosition() || I->isDebugValue() ||
+                    TII->isBasicBlockPrologue(*I)))
     ++I;
   // FIXME: This needs to change if we wish to bundle labels / dbg_values
   // inside the bundle.
@@ -225,7 +232,7 @@ StringRef MachineBasicBlock::getName() const {
   if (const BasicBlock *LBB = getBasicBlock())
     return LBB->getName();
   else
-    return "(null)";
+    return StringRef("", 0);
 }
 
 /// Return a hopefully unique identifier for this block.
@@ -417,7 +424,7 @@ void MachineBasicBlock::updateTerminator() {
 
   MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
   SmallVector<MachineOperand, 4> Cond;
-  DebugLoc DL;  // FIXME: this is nowhere
+  DebugLoc DL = findBranchDebugLoc();
   bool B = TII->analyzeBranch(*this, TBB, FBB, Cond);
   (void) B;
   assert(!B && "UpdateTerminators requires analyzable predecessors!");
@@ -485,7 +492,7 @@ void MachineBasicBlock::updateTerminator() {
       // FIXME: This does not seem like a reasonable pattern to support, but it
       // has been seen in the wild coming out of degenerate ARM test cases.
       TII->removeBranch(*this);
-  
+
       // Finally update the unconditional successor to be reached via a branch if
       // it would not be reached by fallthrough.
       if (!isLayoutSuccessor(TBB))
@@ -681,16 +688,16 @@ bool MachineBasicBlock::isLayoutSuccessor(const MachineBasicBlock *MBB) const {
   return std::next(I) == MachineFunction::const_iterator(MBB);
 }
 
-bool MachineBasicBlock::canFallThrough() {
+MachineBasicBlock *MachineBasicBlock::getFallThrough() {
   MachineFunction::iterator Fallthrough = getIterator();
   ++Fallthrough;
   // If FallthroughBlock is off the end of the function, it can't fall through.
   if (Fallthrough == getParent()->end())
-    return false;
+    return nullptr;
 
   // If FallthroughBlock isn't a successor, no fallthrough is possible.
   if (!isSuccessor(&*Fallthrough))
-    return false;
+    return nullptr;
 
   // Analyze the branches, if any, at the end of the block.
   MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
@@ -702,25 +709,31 @@ bool MachineBasicBlock::canFallThrough() {
     // is possible. The isPredicated 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.
-    return empty() || !back().isBarrier() || TII->isPredicated(back());
+    return (empty() || !back().isBarrier() || TII->isPredicated(back()))
+               ? &*Fallthrough
+               : nullptr;
   }
 
   // If there is no branch, control always falls through.
-  if (!TBB) return true;
+  if (!TBB) return &*Fallthrough;
 
   // If there is some explicit branch to the fallthrough block, it can obviously
   // reach, even though the branch should get folded to fall through implicitly.
   if (MachineFunction::iterator(TBB) == Fallthrough ||
       MachineFunction::iterator(FBB) == Fallthrough)
-    return true;
+    return &*Fallthrough;
 
   // If it's an unconditional branch to some block not the fall through, it
   // doesn't fall through.
-  if (Cond.empty()) return false;
+  if (Cond.empty()) return nullptr;
 
   // Otherwise, if it is conditional and has no explicit false block, it falls
   // through.
-  return FBB == nullptr;
+  return (FBB == nullptr) ? &*Fallthrough : nullptr;
+}
+
+bool MachineBasicBlock::canFallThrough() {
+  return getFallThrough() != nullptr;
 }
 
 MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ,
@@ -1144,6 +1157,24 @@ MachineBasicBlock::findDebugLoc(instr_iterator MBBI) {
   return {};
 }
 
+/// Find and return the merged DebugLoc of the branch instructions of the block.
+/// Return UnknownLoc if there is none.
+DebugLoc
+MachineBasicBlock::findBranchDebugLoc() {
+  DebugLoc DL;
+  auto TI = getFirstTerminator();
+  while (TI != end() && !TI->isBranch())
+    ++TI;
+
+  if (TI != end()) {
+    DL = TI->getDebugLoc();
+    for (++TI ; TI != end() ; ++TI)
+      if (TI->isBranch())
+        DL = DILocation::getMergedLocation(DL, TI->getDebugLoc());
+  }
+  return DL;
+}
+
 /// Return probability of the edge from this block to MBB.
 BranchProbability
 MachineBasicBlock::getSuccProbability(const_succ_iterator Succ) const {