[MachineBasicBlock] Fix update of live intervals in splitAt

[critson]

Summary

In splitAt the wrong insertion point is passed to insertMBBInMaps.

[arsenm]

Any test?

[critson]

• Add tests, but these depend on D91066

[critson]

Rebase

[critson]

Superseded by D94311.

llvm/lib/CodeGen/MachineBasicBlock.cpp

MachineBasicBlock *MachineBasicBlock::splitAt(MachineInstr &MI,
 
   SplitBB->transferSuccessorsAndUpdatePHIs(this);
   addSuccessor(SplitBB);
 
   if (UpdateLiveIns)
     addLiveIns(*SplitBB, LiveRegs);
 
   if (LIS)
-    LIS->insertMBBInMaps(SplitBB, &MI);
+    LIS->insertMBBInMaps(SplitBB, &*SplitPoint);
 
   return SplitBB;
 }
 
 MachineBasicBlock *MachineBasicBlock::SplitCriticalEdge(
     MachineBasicBlock *Succ, Pass &P,
     std::vector<SparseBitVector<>> *LiveInSets) {
   if (!canSplitCriticalEdge(Succ))

llvm/unittests/MI/LiveIntervalTest.cpp

 #include "llvm/ADT/STLExtras.h"
 #include "llvm/CodeGen/LiveIntervals.h"
 #include "llvm/CodeGen/MIRParser/MIRParser.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Support/MemoryBuffer.h"
static void testHandleMoveIntoNewBundle(MachineFunction &MF, LiveIntervals &LIS,
   // Build bundle
   finalizeBundle(MBB, I, std::next(ToInstr.getIterator()));
 
   // Update LiveIntervals
   MachineBasicBlock::instr_iterator BundleStart = std::prev(I);
   LIS.handleMoveIntoNewBundle(*BundleStart, true);
 }
 
+/**
+ * Split block numbered \p BlockNum at instruction \p SplitAt using
+ * MachineBasicBlock::splitAt updating liveness intervals.
+ */
+static void testSplitAt(MachineFunction &MF, LiveIntervals &LIS,
+                        unsigned SplitAt, unsigned BlockNum) {
+  MachineInstr &SplitInstr = getMI(MF, SplitAt, BlockNum);
+  MachineBasicBlock &MBB = *SplitInstr.getParent();
+
+  // Split block and update live intervals
+  MBB.splitAt(SplitInstr, false, &LIS);
+}
+
 static void liveIntervalTest(StringRef MIRFunc, LiveIntervalTest T) {
   LLVMContext Context;
   std::unique_ptr<LLVMTargetMachine> TM = createTargetMachine();
   // This test is designed for the X86 backend; stop if it is not available.
   if (!TM)
     return;
 
   legacy::PassManager PM;
bb.1:
     S_NOP 0, implicit %0.sub1
   bb.2:
     S_NOP 0, implicit %0.sub1
 )MIR", [](MachineFunction &MF, LiveIntervals &LIS) {
     testHandleMoveIntoNewBundle(MF, LIS, 0, 1, 0);
   });
 }
 
+TEST(LiveIntervalTest, SplitAtOneInstruction) {
+  liveIntervalTest(R"MIR(
+    successors: %bb.1
+    %0 = IMPLICIT_DEF
+    S_BRANCH %bb.1
+  bb.1:
+    S_NOP 0
+)MIR", [](MachineFunction &MF, LiveIntervals &LIS) {
+    testSplitAt(MF, LIS, 1, 0);
+  });
+}
+
+TEST(LiveIntervalTest, SplitAtMultiInstruction) {
+  liveIntervalTest(R"MIR(
+    successors: %bb.1
+    %0 = IMPLICIT_DEF
+    S_NOP 0
+    S_NOP 0
+    S_NOP 0
+    S_NOP 0
+    S_BRANCH %bb.1
+  bb.1:
+    S_NOP 0
+)MIR", [](MachineFunction &MF, LiveIntervals &LIS) {
+    testSplitAt(MF, LIS, 0, 0);
+  });
+}
+
 int main(int argc, char **argv) {
   ::testing::InitGoogleTest(&argc, argv);
   initLLVM();
   return RUN_ALL_TESTS();
 }