[regalloc] Fix liverange bundle TryMerge to merge connected UseIntervals

The current bundle merge check on uses does not merge UseInterval starting from the other UserInterval's end.
This is incorrect and will miss some bundle merge opportunties.

Change-Id: I0b828f83cfe7ae401e3c0c40dc94aa3787f2e05e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2059570
Commit-Queue: Yolanda Chen <yolanda.chen@intel.com>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66404}

src/compiler/backend/register-allocator.cc

@@ -2808,9 +2808,9 @@ bool LiveRangeBundle::TryMerge(LiveRangeBundle* other, bool trace_alloc) {
   auto iter2 = other->uses_.begin();
 
   while (iter1 != uses_.end() && iter2 != other->uses_.end()) {
-    if (iter1->start > iter2->end) {
+    if (iter1->start >= iter2->end) {
       ++iter2;
-    } else if (iter2->start > iter1->end) {
+    } else if (iter2->start >= iter1->end) {
       ++iter1;
     } else {
       TRACE_COND(trace_alloc, "No merge %d:%d %d:%d\n", iter1->start,

src/compiler/backend/register-allocator.h

@@ -721,6 +721,7 @@ class LiveRangeBundle : public ZoneObject {
  private:
   friend class BundleBuilder;
 
+  // Representation of the non-empty interval [start,end[.
   class Range {
    public:
     Range(int s, int e) : start(s), end(e) {}