[SimpleLoopUnswitch] Skip trivial select conds for selects

Fixes https://github.com/llvm/llvm-project/issues/62715

If a select's condition is a trivial select:
```
%s = select %cond, i1 true, i1 false
```
Unswitch on %cond, rather than %s. This fixes crashes where there is a
disparity in finding candidates and and the transformation logic.

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
index e15ee81..b3ebfaa 100644
--- a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
@@ -2872,7 +2872,7 @@ static bool collectUnswitchCandidates(
 
     for (auto &I : *BB) {
       if (auto *SI = dyn_cast<SelectInst>(&I)) {
-        auto *Cond = SI->getCondition();
+        auto *Cond = skipTrivialSelect(SI->getCondition());
         // restrict to simple boolean selects
         if (!isa<Constant>(Cond) && L.isLoopInvariant(Cond) && Cond->getType()->isIntegerTy(1))
           UnswitchCandidates.push_back({&I, {Cond}});