Implemented stack symbol table ordering/packing optimization to improve data locality and code size from SP/FP offset encoding.

Differential Revision: http://reviews.llvm.org/D15393

llvm-svn: 260917

1 files changed, 14 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index 8a4df422294..14a2d0800a5 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -707,8 +707,10 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
                           Offset, MaxAlign, Skew);
   }
 
-  // Then assign frame offsets to stack objects that are not used to spill
-  // callee saved registers.
+  SmallVector<int, 8> ObjectsToAllocate;
+
+  // Then prepare to 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) &&
         MFI->getUseLocalStackAllocationBlock())
@@ -724,8 +726,17 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
     if (ProtectedObjs.count(i))
       continue;
 
-    AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign, Skew);
+    // Add the objects that we need to allocate to our working set.
+    ObjectsToAllocate.push_back(i);
   }
+  // Give the targets a chance to order the objects the way they like it.
+  if (Fn.getTarget().getOptLevel() != CodeGenOpt::None &&
+      Fn.getTarget().Options.StackSymbolOrdering)
+    TFI.orderFrameObjects(Fn, ObjectsToAllocate);
+  
+  // Now walk the objects and actually assign base offsets to them.
+  for (auto &Object : ObjectsToAllocate)
+    AdjustStackOffset(MFI, Object, StackGrowsDown, Offset, MaxAlign, Skew);
 
   // Make sure the special register scavenging spill slot is closest to the
   // stack pointer.