[llvm] [RemoveDIs] Handle DPValues in hoistCommonCodeFromSuccessors (PR #79476)

[Stephen Tozer via llvm-commits]

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@@ -1660,18 +1722,25 @@ bool SimplifyCFGOpt::hoistCommonCodeFromSuccessors(BasicBlock *BB,
         // The debug location is an integral part of a debug info intrinsic
         // and can't be separated from it or replaced.  Instead of attempting
         // to merge locations, simply hoist both copies of the intrinsic.
-        I1->moveBeforePreserving(TI);
+        hoistLockstepIdenticalDPValues(TI, I1, OtherInsts);
+        // We've just hoisted DPValues; move I1 after them (before TI) and
+        // leave any that were not hoisted behind (by calling moveBefore
+        // rather than moveBeforePreserving).
+        I1->moveBefore(TI);
         for (auto &SuccIter : OtherSuccIterRange) {
           auto *I2 = &*SuccIter++;
           assert(isa<DbgInfoIntrinsic>(I2));
-          I2->moveBeforePreserving(TI);
+          I2->moveBefore(TI);
         }
       } else {
         // For a normal instruction, we just move one to right before the
         // branch, then replace all uses of the other with the first.  Finally,
-        // we remove the now redundant second instruction.
-        I1->moveBeforePreserving(TI);
-        BB->splice(TI->getIterator(), BB1, I1->getIterator());
+        // we remove the now redundant second instruction.s
----------------
SLTozer wrote:

```suggestion
        // we remove the now redundant second instruction.
```

https://github.com/llvm/llvm-project/pull/79476