3 files changed, 28 insertions, 3 deletions

diff --git a/llvm/include/llvm/CodeGen/MachineFrameInfo.h b/llvm/include/llvm/CodeGen/MachineFrameInfo.h
index ba5d6ba97eb..f8bf14ab018 100644
--- a/llvm/include/llvm/CodeGen/MachineFrameInfo.h
+++ b/llvm/include/llvm/CodeGen/MachineFrameInfo.h
@@ -216,6 +216,11 @@ class MachineFrameInfo {
   /// alignment of any object in it.
   unsigned LocalFrameMaxAlign;
 
+  /// Whether the local object blob needs to be allocated together. If not,
+  /// PEI should ignore the isPreAllocated flags on the stack objects and
+  /// just allocate them normally.
+  bool UseLocalStackAllocationBlock;
+
 public:
     explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
     StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
@@ -315,6 +320,17 @@ public:
   /// object blob.
   unsigned getLocalFrameMaxAlign() { return LocalFrameMaxAlign; }
 
+  /// getUseLocalStackAllocationBlock - Get whether the local allocation blob
+  /// should be allocated together or let PEI allocate the locals in it
+  /// directly.
+  bool getUseLocalStackAllocationBlock() {return UseLocalStackAllocationBlock;}
+
+  /// setUseLocalStackAllocationBlock - Set whether the local allocation blob
+  /// should be allocated together or let PEI allocate the locals in it
+  /// directly.
+  void setUseLocalStackAllocationBlock(bool v) {
+    UseLocalStackAllocationBlock = v;
+  }
 
   /// isObjectPreAllocated - Return true if the object was pre-allocated into
   /// the local block.
diff --git a/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp b/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
index b7071dec474..a4a43875cee 100644
--- a/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
+++ b/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
@@ -89,6 +89,13 @@ bool LocalStackSlotPass::runOnMachineFunction(MachineFunction &MF) {
   // Insert virtual base registers to resolve frame index references.
   insertFrameReferenceRegisters(MF);
 
+  // Tell MFI whether any base registers were allocated. PEI will only
+  // want to use the local block allocations from this pass if there were any.
+  // Otherwise, PEI can do a bit better job of getting the alignment right
+  // without a hole at the start since it knows the alignment of the stack
+  // at the start of local allocation, and this pass doesn't.
+  MFI->setUseLocalStackAllocationBlock(NumBaseRegisters > 0);
+
   return true;
 }
 
diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index 569faceffdc..4b8a4b5562f 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -560,7 +560,7 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
   // check for whether the frame is large enough to want to use virtual
   // frame index registers. Functions which don't want/need this optimization
   // will continue to use the existing code path.
-  if (EnableLocalStackAlloc && MFI->getLocalFrameSize()) {
+  if (EnableLocalStackAlloc && MFI->getUseLocalStackAllocationBlock()) {
     unsigned Align = MFI->getLocalFrameMaxAlign();
 
     // Adjust to alignment boundary.
@@ -593,7 +593,8 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
 
     // Assign large stack objects first.
     for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
-      if (MFI->isObjectPreAllocated(i))
+      if (MFI->isObjectPreAllocated(i) &&
+          MFI->getUseLocalStackAllocationBlock())
         continue;
       if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
         continue;
@@ -614,7 +615,8 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
   // Then assign frame offsets to stack objects that are not used to spill
   // callee saved registers.
   for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
-    if (MFI->isObjectPreAllocated(i))
+    if (MFI->isObjectPreAllocated(i) &&
+        MFI->getUseLocalStackAllocationBlock())
       continue;
     if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
       continue;