am 31675153: Merge branch \'upstream\' into merge_2

* commit '31675153bd2d7617db8cb6aeb58054934c7b9f73': (542 commits)
  MaximumSpanningTree::EdgeWeightCompare: Make this comparator actually be a strict weak ordering, and don't pass possibly-null pointers to dyn_cast.
  Fix misaligned access in MachO object file reader: despite containing an int64_t, Symbol64TableEntry is actually only stored with 4-byte alignment within the file.
  Fix unaligned memory accesses when performing relocations in X86 JIT. There's no cost to using memcpy here: the fixed code is optimized by LLVM to perfect machine code.
  Don't pass a null pointer to cast<> in its unit tests.
  Don't bind a reference to a dereferenced null pointer (for return value of WeakVH::operator*).
  [ms-inline asm] Do not report a Parser error when matching inline assembly.
  Ignore the documentation-suggested location for compile_commands.json
  The presence of the empty file "foo" unfortunately does not improve LLVM in any way.
  Remove unnecessary cast that was also unnecessarily casting away constness.
  Provide a portability macro for __builtin_trap.
  Fix macros arguments with an underscore, dot or dollar in them. This is based on a patch by Andy/PaX. I added the support for dot and dollar.
  [ms-inline asm] Expose the ErrorInfo from the MatchInstructionImpl.  In general, this is the index of the operand that failed to match.
  Formatting.  No functional change.
  Make the wording in of the "expected identifier" error in the .macro directive consistent with the other "expected identifier" errors. Extracted from the Andy/PaX patch. I added the test.
  Pacify PVS-Studio by changing the type rather than doing a cast, a tweak suggested by David Blaikie.
  Add support for the --param ssp-buffer-size= driver option. PR9673
  Use typedefs. Fix indentation. Extracted from the Andy/PaX patch.
  Remove unused variable. Extracted from the Andy/PaX patch.
  Fix typo. Extracted from the Andy/PaX patch.
  MCJIT: Tidy up the constructor.
  ...

1 files changed, 57 insertions, 13 deletions

diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index 277c4d5..a8deda8 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -66,11 +66,6 @@ static cl::opt<bool> DisableBranchOpts(
   "disable-cgp-branch-opts", cl::Hidden, cl::init(false),
   cl::desc("Disable branch optimizations in CodeGenPrepare"));
 
-// FIXME: Remove this abomination once all of the tests pass without it!
-static cl::opt<bool> DisableDeleteDeadBlocks(
-  "disable-cgp-delete-dead-blocks", cl::Hidden, cl::init(false),
-  cl::desc("Disable deleting dead blocks in CodeGenPrepare"));
-
 static cl::opt<bool> DisableSelectToBranch(
   "disable-cgp-select2branch", cl::Hidden, cl::init(false),
   cl::desc("Disable select to branch conversion."));
@@ -116,6 +111,7 @@ namespace {
     }
 
   private:
+    bool EliminateFallThrough(Function &F);
     bool EliminateMostlyEmptyBlocks(Function &F);
     bool CanMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
     void EliminateMostlyEmptyBlock(BasicBlock *BB);
@@ -187,10 +183,14 @@ bool CodeGenPrepare::runOnFunction(Function &F) {
           WorkList.insert(*II);
     }
 
-    if (!DisableDeleteDeadBlocks)
-      for (SmallPtrSet<BasicBlock*, 8>::iterator
-             I = WorkList.begin(), E = WorkList.end(); I != E; ++I)
-        DeleteDeadBlock(*I);
+    for (SmallPtrSet<BasicBlock*, 8>::iterator
+           I = WorkList.begin(), E = WorkList.end(); I != E; ++I)
+      DeleteDeadBlock(*I);
+
+    // Merge pairs of basic blocks with unconditional branches, connected by
+    // a single edge.
+    if (EverMadeChange || MadeChange)
+      MadeChange |= EliminateFallThrough(F);
 
     if (MadeChange)
       ModifiedDT = true;
@@ -203,6 +203,39 @@ bool CodeGenPrepare::runOnFunction(Function &F) {
   return EverMadeChange;
 }
 
+/// EliminateFallThrough - Merge basic blocks which are connected
+/// by a single edge, where one of the basic blocks has a single successor
+/// pointing to the other basic block, which has a single predecessor.
+bool CodeGenPrepare::EliminateFallThrough(Function &F) {
+  bool Changed = false;
+  // Scan all of the blocks in the function, except for the entry block.
+  for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ) {
+    BasicBlock *BB = I++;
+    // If the destination block has a single pred, then this is a trivial
+    // edge, just collapse it.
+    BasicBlock *SinglePred = BB->getSinglePredecessor();
+
+    if (!SinglePred || SinglePred == BB) continue;
+
+    BranchInst *Term = dyn_cast<BranchInst>(SinglePred->getTerminator());
+    if (Term && !Term->isConditional()) {
+      Changed = true;
+      DEBUG(dbgs() << "To merge:\n"<< *SinglePred << "\n\n\n");
+      // Remember if SinglePred was the entry block of the function.
+      // If so, we will need to move BB back to the entry position.
+      bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
+      MergeBasicBlockIntoOnlyPred(BB, this);
+
+      if (isEntry && BB != &BB->getParent()->getEntryBlock())
+        BB->moveBefore(&BB->getParent()->getEntryBlock());
+
+      // We have erased a block. Update the iterator.
+      I = BB;
+    }
+  }
+  return Changed;
+}
+
 /// EliminateMostlyEmptyBlocks - eliminate blocks that contain only PHI nodes,
 /// debug info directives, and an unconditional branch.  Passes before isel
 /// (e.g. LSR/loopsimplify) often split edges in ways that are non-optimal for
@@ -610,7 +643,7 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
   // that have the default "don't know" as the objectsize.  Anything else
   // should be left alone.
   CodeGenPrepareFortifiedLibCalls Simplifier;
-  return Simplifier.fold(CI, TD);
+  return Simplifier.fold(CI, TD, TLInfo);
 }
 
 /// DupRetToEnableTailCallOpts - Look for opportunities to duplicate return
@@ -645,10 +678,18 @@ bool CodeGenPrepare::DupRetToEnableTailCallOpts(ReturnInst *RI) {
   if (!TLI)
     return false;
 
+  PHINode *PN = 0;
+  BitCastInst *BCI = 0;
   Value *V = RI->getReturnValue();
-  PHINode *PN = V ? dyn_cast<PHINode>(V) : NULL;
-  if (V && !PN)
-    return false;
+  if (V) {
+    BCI = dyn_cast<BitCastInst>(V);
+    if (BCI)
+      V = BCI->getOperand(0);
+
+    PN = dyn_cast<PHINode>(V);
+    if (!PN)
+      return false;
+  }
 
   BasicBlock *BB = RI->getParent();
   if (PN && PN->getParent() != BB)
@@ -666,6 +707,9 @@ bool CodeGenPrepare::DupRetToEnableTailCallOpts(ReturnInst *RI) {
   if (PN) {
     BasicBlock::iterator BI = BB->begin();
     do { ++BI; } while (isa<DbgInfoIntrinsic>(BI));
+    if (&*BI == BCI)
+      // Also skip over the bitcast.
+      ++BI;
     if (&*BI != RI)
       return false;
   } else {