Yingwei Zheng c89d731c5d [LVI] Infer non-zero from equality icmp (#112838) ...

This following pattern is common in loop headers:
```
  %101 = sub nuw i64 %78, %98
  %103 = icmp eq i64 %78, %98
  br i1 %103, label %.thread.i.i, label %.preheader.preheader.i.i

.preheader.preheader.i.i:
  %invariant.umin.i.i = call i64 @llvm.umin.i64(i64 %101, i64 9)
  %umax.i = call i64 @llvm.umax.i64(i64 %invariant.umin.i.i, i64 1)
  br label %.preheader.i.i

.preheader.i.i:
  ...
  %116 = add nuw nsw i64 %.011.i.i, 1
  %exitcond.not.i = icmp eq i64 %116, %umax.i
  br i1 %exitcond.not.i, label %.critedge.i.i, label %.preheader.i.i
```
As `%78` is not equal to `%98` in BB `.preheader.preheader.i.i`, we can
prove `%101` is non-zero. Then we can simplify the loop exit condition.

Addresses regression introduced by
https://github.com/llvm/llvm-project/pull/112742.

2024-10-18 21:19:02 +08:00

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