Joshua Cao 629d880dc5 [LoopUnrollAndJam] Visit phi operand dependencies in post-order ...

Fixes https://github.com/llvm/llvm-project/issues/58565

The previous implementation visits operands in pre-order, but this does
not guarantee an instruction is visited before its uses. This can cause
instructions to be copied in the incorrect order. For example:

```
a = ...
b = add a, 1
c = add a, b
d = add b, a
```

Pre-order visits does not guarantee the order in which `a` and `b` are
visited. LoopUnrollAndJam may incorrectly insert `b` before `a`.

This patch implements post-order visits. By visiting dependencies first,
we guarantee that an instruction's dependencies are visited first.

Differential Revision: https://reviews.llvm.org/D140255

2023-01-05 00:05:49 -08:00

38 KiB

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