Add tags to live interval unions to avoid using stale queries.

The tag is updated whenever the live interval union is changed, and it is tested
before using cached information.

llvm-svn: 125224

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/LiveIntervalUnion.cpp b/llvm/lib/CodeGen/LiveIntervalUnion.cpp
index 2027db19b75..205f28a0d65 100644
--- a/llvm/lib/CodeGen/LiveIntervalUnion.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalUnion.cpp
@@ -28,6 +28,7 @@ using namespace llvm;
 void LiveIntervalUnion::unify(LiveInterval &VirtReg) {
   if (VirtReg.empty())
     return;
+  ++Tag;
 
   // Insert each of the virtual register's live segments into the map.
   LiveInterval::iterator RegPos = VirtReg.begin();
@@ -46,6 +47,7 @@ void LiveIntervalUnion::unify(LiveInterval &VirtReg) {
 void LiveIntervalUnion::extract(LiveInterval &VirtReg) {
   if (VirtReg.empty())
     return;
+  ++Tag;
 
   // Remove each of the virtual register's live segments from the map.
   LiveInterval::iterator RegPos = VirtReg.begin();