[PATCH] D113079: [InstCombine] Take arguments into consideration when simplify range check

[guopeilin via Phabricator via llvm-commits]

guopeilin added a comment.

Sorry for the absence of the description.
Actually, it is a runtime error. The simplify range check optimization will change `(icmp slt x, 0) | (icmp sgt x, n) ` into `icmp ugt x, n`
Now, suppose the %0 is `negative`, Before optimizing, we will compare the argument with 0 to see whether the argument is less than 0, if so, we will finally return `shl i32 %0, 0`. 
However, after optimizing, we will not have this comparison, and we will finally return `shl i32 %0, %and`. The problem is that `%and` is also driven from the argument, it can be undefined cause it is a shift operation that depends on the argument. So, after optimization, we will get an undefined result.
So, I guess that if both `x` and `n` in `(icmp slt x, 0) | (icmp sgt x, n) ` are derived from the argument, then we should be conservative.


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https://reviews.llvm.org/D113079