Update local stack block allocation to let PEI do the allocs if no additional

base registers were required. This will allow for slightly better packing
of the locals when alignment padding is necessary after callee saved registers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111508 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/MachineFrameInfo.h b/include/llvm/CodeGen/MachineFrameInfo.h
index ba5d6ba97ebf00d8e0163c894113ca992c55e2cd..f8bf14ab018851cffbce025447bf235e60cbc0a0 100644 (file)
--- a/include/llvm/CodeGen/MachineFrameInfo.h
+++ b/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/lib/CodeGen/LocalStackSlotAllocation.cpp b/lib/CodeGen/LocalStackSlotAllocation.cpp
index b7071dec474b3aa31fdc410b4ec43a23c7cff706..a4a43875ceed5719d5e2608dea68596de6c1292c 100644 (file)
--- a/lib/CodeGen/LocalStackSlotAllocation.cpp
+++ b/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/lib/CodeGen/PrologEpilogInserter.cpp b/lib/CodeGen/PrologEpilogInserter.cpp
index 569faceffdc7ae6ea0e8c69ad800bb23745b76a2..4b8a4b5562ff6459c6e54347b24142ba817fee2c 100644 (file)
--- a/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/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;