RFR: 8357434: x86: Simplify Interpreter::profile_taken_branch

[Vladimir Ivanov]

On Wed, 21 May 2025 08:23:14 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Noticed that `Interpreter::profile_taken_branch` has the same `sbbptr` pattern we have eliminated with [JDK-8356946](https://bugs.openjdk.org/browse/JDK-8356946). The same logic applies here: the counter is 64-bit, never practically overflows, and no other code cares about it.
> 
> Also tidied up some comments around it.
> 
> Additional testing;
>  - [x] Linux x86_64 server fastdebug, `tier1 tier2`

src/hotspot/cpu/x86/templateTable_x86.cpp line 1690:

> 1688: void TemplateTable::branch(bool is_jsr, bool is_wide) {
> 1689:   __ get_method(rcx); // rcx holds method
> 1690:   __ profile_taken_branch(rax); // rax holds updated MDP

Stale comment at line 1741? Otherwise, looks good.


 if (UseLoopCounter) {
    // increment backedge counter for backward branches
    // rax: MDO
    // rbx: MDO bumped taken-count

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PR Review Comment: https://git.openjdk.org/jdk/pull/25343#discussion_r2110003697