[PATCH] D32407: [JumpThread] Do RAUW in case Cond folds to a constant in the CFG

[Sanjoy Das via Phabricator via llvm-commits]

sanjoy accepted this revision.
sanjoy added a comment.
This revision is now accepted and ready to land.

lgtm with nits



================
Comment at: lib/Transforms/Scalar/JumpThreading.cpp:1252
   BasicBlock *OnlyDest = nullptr;
   BasicBlock *MultipleDestSentinel = (BasicBlock*)(intptr_t)~0ULL;
+  Constant *OnlyVal = nullptr;
----------------
Separately, it may be better to use `DenseMapInfo<BasicBlock *>::getTombStoneKey()` here.


================
Comment at: lib/Transforms/Scalar/JumpThreading.cpp:1322
       // erase it.
       auto *CondInst = dyn_cast<Instruction>(Cond);
       if (CondInst && CondInst->use_empty())
----------------
I'd structure this as:

```
if (auto *CondInst = dyn_cast<Instruction>(Cond)) {
  if (CondInst->use_empty()) {
  } else if (OnlyVal && ...) {
  }
}
```


Another thing is that this code needs to check `!CondInst->mayHaveSideEffects()` before removing it.


================
Comment at: test/Transforms/JumpThreading/fold-not-thread.ll:142
+entry:
+  %cmp = icmp eq i32 %value, 32
+  br i1 %cmp, label %L0, label %L3 
----------------
Please also add a negative test where `%add = add i32 %value, 64` is not in L0.


https://reviews.llvm.org/D32407