commit b2597268c215e2349905c81bfc22f69849b5ab18
author Jakob Stoklund Olesen <stoklund@2pi.dk> Thu Feb 24 01:07:55 2011 +0000
committer Jakob Stoklund Olesen <stoklund@2pi.dk> Thu Feb 24 01:07:55 2011 +0000
tree 7f0335ab95458fdbd924246a13f71395dcab1266
parent fae7f6de9ec18a6a8331b7ddbf51fd5f5c3e4288

Use the same spill slot for all live ranges that descend form the same original
register.

This avoids some silly stack slot shuffling when both sides of a copy get
spilled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126353 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/InlineSpiller.cpp

diff --git a/lib/CodeGen/InlineSpiller.cpp b/lib/CodeGen/InlineSpiller.cpp
index ba37e54..38e6c85 100644
--- a/lib/CodeGen/InlineSpiller.cpp
+++ b/lib/CodeGen/InlineSpiller.cpp
@@ -345,7 +345,8 @@
          && "Trying to spill a stack slot.");
   DEBUG(dbgs() << "Inline spilling "
                << mri_.getRegClass(edit.getReg())->getName()
-               << ':' << edit.getParent() << "\n");
+               << ':' << edit.getParent() << "\nFrom original "
+               << PrintReg(vrm_.getOriginal(edit.getReg())) << '\n');
   assert(edit.getParent().isSpillable() &&
          "Attempting to spill already spilled value.");
 
@@ -356,12 +357,20 @@
     return;
 
   rc_ = mri_.getRegClass(edit.getReg());
-  stackSlot_ = vrm_.assignVirt2StackSlot(edit_->getReg());
+
+  // Share a stack slot among all descendants of Orig.
+  unsigned Orig = vrm_.getOriginal(edit.getReg());
+  stackSlot_ = vrm_.getStackSlot(Orig);
+  if (stackSlot_ == VirtRegMap::NO_STACK_SLOT)
+    stackSlot_ = vrm_.assignVirt2StackSlot(Orig);
+
+  if (Orig != edit.getReg())
+    vrm_.assignVirt2StackSlot(edit.getReg(), stackSlot_);
 
   // Update LiveStacks now that we are committed to spilling.
   LiveInterval &stacklvr = lss_.getOrCreateInterval(stackSlot_, rc_);
-  assert(stacklvr.empty() && "Just created stack slot not empty");
-  stacklvr.getNextValue(SlotIndex(), 0, lss_.getVNInfoAllocator());
+  if (!stacklvr.hasAtLeastOneValue())
+    stacklvr.getNextValue(SlotIndex(), 0, lss_.getVNInfoAllocator());
   stacklvr.MergeRangesInAsValue(edit_->getParent(), stacklvr.getValNumInfo(0));
 
   // Iterate over instructions using register.