LiveIntervalAnalysis: Fix handleMove() re-using the wrong value number

This fixes http://llvm.org/PR27856

llvm-svn: 270619

2 files changed, 27 insertions, 9 deletions

diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index 16d0030a346..2358b0e7464 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -1257,20 +1257,16 @@ private:
           // value.
           LiveRange::iterator NewSegment = NewIdxIn;
           LiveRange::iterator Next = std::next(NewSegment);
-          NewSegment->valno = OldIdxVNI;
           if (SlotIndex::isEarlierInstr(Next->start, NewIdx)) {
             // There is no gap between NewSegment and its predecessor.
             *NewSegment = LiveRange::Segment(Next->start, SplitPos,
-                                             NewSegment->valno);
-            NewSegment->valno->def = Next->start;
-
-            *Next = LiveRange::Segment(SplitPos, Next->end, Next->valno);
+                                             Next->valno);
+            *Next = LiveRange::Segment(SplitPos, Next->end, OldIdxVNI);
             Next->valno->def = SplitPos;
           } else {
             // There is a gap between NewSegment and its predecessor
             // Value becomes live in.
-            *NewSegment = LiveRange::Segment(SplitPos, Next->start,
-                                             NewSegment->valno);
+            *NewSegment = LiveRange::Segment(SplitPos, Next->start, OldIdxVNI);
             NewSegment->valno->def = SplitPos;
           }
         } else {
diff --git a/llvm/unittests/MI/LiveIntervalTest.cpp b/llvm/unittests/MI/LiveIntervalTest.cpp
index dc555c1e610..e4567363d39 100644
--- a/llvm/unittests/MI/LiveIntervalTest.cpp
+++ b/llvm/unittests/MI/LiveIntervalTest.cpp
@@ -109,8 +109,8 @@ private:
  * update affected liveness intervals with LiveIntervalAnalysis::handleMove().
  */
 static void testHandleMove(MachineFunction &MF, LiveIntervals &LIS,
-                           unsigned From, unsigned To) {
-  MachineBasicBlock &MBB = MF.front();
+                           unsigned From, unsigned To, unsigned BlockNum = 0) {
+  MachineBasicBlock &MBB = *MF.getBlockNumbered(BlockNum);
 
   unsigned I = 0;
   MachineInstr *FromInstr = nullptr;
@@ -307,6 +307,28 @@ TEST(LiveIntervalTest, MoveUndefUse) {
   });
 }
 
+TEST(LiveIntervalTest, MoveUpValNos) {
+  // handleMoveUp() had a bug where it would reuse the value number of the
+  // destination segment, even though we have no guarntee that this valno wasn't
+  // used in other segments.
+  liveIntervalTest(
+"    successors: %bb.1, %bb.2\n"
+"    %0 = IMPLICIT_DEF\n"
+"    JG_1 %bb.2, implicit %eflags\n"
+"    JMP_1 %bb.1\n"
+"  bb.2:\n"
+"    NOOP implicit %0\n"
+"  bb.1:\n"
+"    successors: %bb.2\n"
+"    %0 = IMPLICIT_DEF implicit %0(tied-def 0)\n"
+"    %0 = IMPLICIT_DEF implicit %0(tied-def 0)\n"
+"    %0 = IMPLICIT_DEF implicit %0(tied-def 0)\n"
+"    JMP_1 %bb.2\n",
+  [](MachineFunction &MF, LiveIntervals &LIS) {
+    testHandleMove(MF, LIS, 2, 0, 2);
+  });
+}
+
 int main(int argc, char **argv) {
   ::testing::InitGoogleTest(&argc, argv);
   initLLVM();