[NFC] Refactor looping over recomputeLiveIns into function (#88040)

https://github.com/llvm/llvm-project/pull/79940 put calls to
recomputeLiveIns into
a loop, to repeatedly call the function until the computation converges.
However,
this repeats a lot of code. This changes moves the loop into a function
to simplify
the handling.

Note that this changes the order in which recomputeLiveIns is called.
For example,

```
  bool anyChange = false;
  do {
    anyChange = recomputeLiveIns(*ExitMBB) || recomputeLiveIns(*LoopMBB);
  } while (anyChange);
```

only begins to recompute the live-ins for LoopMBB after the computation
for ExitMBB
has converged. With this change, all basic blocks have a recomputation
of the live-ins
for each loop iteration. This can result in less or more calls,
depending on the
situation.

1 files changed, 2 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index ecf7bc3..55aa1d4 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -2047,12 +2047,8 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
   MBB->splice(Loc, TBB, TBB->begin(), TIB);
   FBB->erase(FBB->begin(), FIB);
 
-  if (UpdateLiveIns) {
-    bool anyChange = false;
-    do {
-      anyChange = recomputeLiveIns(*TBB) || recomputeLiveIns(*FBB);
-    } while (anyChange);
-  }
+  if (UpdateLiveIns)
+    fullyRecomputeLiveIns({TBB, FBB});
 
   ++NumHoist;
   return true;