Provide LiveIntervalUnion::Query::checkLoopInterference.

This is a three-way interval list intersection between a virtual register, a
live interval union, and a loop. It will be used to identify interference-free
loops for live range splitting.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122034 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 28 insertions, 0 deletions

diff --git a/lib/CodeGen/LiveIntervalUnion.cpp b/lib/CodeGen/LiveIntervalUnion.cpp
index 079468a4f0..7ebe96f066 100644
--- a/lib/CodeGen/LiveIntervalUnion.cpp
+++ b/lib/CodeGen/LiveIntervalUnion.cpp
@@ -16,6 +16,7 @@
 #define DEBUG_TYPE "regalloc"
 #include "LiveIntervalUnion.h"
 #include "llvm/ADT/SparseBitVector.h"
+#include "llvm/CodeGen/MachineLoopRanges.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetRegisterInfo.h"
@@ -284,3 +285,30 @@ collectInterferingVRegs(unsigned MaxInterferingRegs) {
   SeenAllInterferences = true;
   return InterferingVRegs.size();
 }
+
+bool LiveIntervalUnion::Query::checkLoopInterference(MachineLoopRange *Loop) {
+  // VirtReg is likely live throughout the loop, so start by checking LIU-Loop
+  // overlaps.
+  IntervalMapOverlaps<LiveIntervalUnion::Map, MachineLoopRange::Map>
+    Overlaps(LiveUnion->getMap(), Loop->getMap());
+  if (!Overlaps.valid())
+    return false;
+
+  // The loop is overlapping an LIU assignment. Check VirtReg as well.
+  LiveInterval::iterator VRI = VirtReg->find(Overlaps.start());
+
+  for (;;) {
+    if (VRI == VirtReg->end())
+      return false;
+    if (VRI->start < Overlaps.stop())
+      return true;
+
+    Overlaps.advanceTo(VRI->start);
+    if (!Overlaps.valid())
+      return false;
+    if (Overlaps.start() < VRI->end)
+      return true;
+
+    VRI = VirtReg->advanceTo(VRI, Overlaps.start());
+  }
+}