RFR: 8281815: x86: Use short jumps in TIG::generate_slow_signature_handler

[Aleksey Shipilev]

On Thu, 17 Feb 2022 08:30:04 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

> On s390, being CISC too, there are similar issues. We addressed them with `NearLabel`, `branch_optimized`, and `compare_and_branch_optimized`. They provide a higher level of abstraction which helps writing better code without knowing all the details, which at least I instantly forget after looking into the manual.

In x86 `MacroAssembler` there are `jcc` and `jccb` for this. When `MacroAssembler` can make `jcc`, it would, but that requires the jump target to be already bound, so that jump offset is already known. For *forward* jumps, though, `MacroAssembler` cannot know this, so in those cases we need to tell it explicitly. `NearLabel` looks like another way of doing so.

-------------

PR: https://git.openjdk.java.net/jdk/pull/7475