RFR: JDK-8290822: C2: assert in PhaseIdealLoop::do_unroll() is subject to undefined behavior

[Tobias Hartmann]

On Wed, 15 Feb 2023 16:13:21 GMT, Tobias Holenstein <tholenstein at openjdk.org> wrote:

> The following assert had undefined behavior (UB) because of _signed_ integer underflow/overflow: 
> 
>     assert(stride_con > 0 && ((limit_type->_hi - stride_con) < limit_type->_hi) || 
>            stride_con < 0 && ((limit_type->_lo - stride_con) > limit_type->_lo), 
>            "sanity"); 
> 
> 
> # Solution 
> The fix is to check for underflow/overflow (the purpose of the assert) without actually underflowing/overflowing.

Looks good to me too.

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Marked as reviewed by thartmann (Reviewer).

PR: https://git.openjdk.org/jdk/pull/12576