RFR: 8362504: AArch64: Replace MOVZ+MOVK+MOVK with ADRP+ADD [v2]

[Andrew Haley]

On Tue, 19 Aug 2025 10:44:12 GMT, Fei Gao <fgao at openjdk.org> wrote:

>> If the relocation or target address is guaranteed to reside within the CodeCache, we can safely replace a `movz + movk + movk` sequence with a more compact and efficient `adrp + add` instruction pair.
>> 
>> In `MacroAssembler::mov(Register r, Address dest)`, this replacement can be applied if any of the following rules hold:
>> 
>> 1. The relocation type indicates that the address resides within the CodeCache and the necessary patching logic is provided in `fix_relocation_after_move()`.
>> 2. The target address is fixed (i.e., does not require relocation) and is within the reachable range for `adrp`.
>> 
>> The patch performs the filtering in `is_relocated_within_codecache()` and `is_adrp_reachable()` to ensure this optimization is applied safely and selectively.
>
> Fei Gao has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Disable reachability-based optimization during AOT code dumping
>  - Merge branch 'master' into replace-mov-with-adrp
>  - 8362504: AArch64: Replace MOVZ+MOVK+MOVK with ADRP+ADD
>    
>    If the relocation or target address is guaranteed to reside within
>    the CodeCache, we can safely replace a `movz + movk + movk`
>    sequence with a more compact and efficient `adrp + add`
>    instruction pair.
>    
>    In `MacroAssembler::mov(Register r, Address dest)`, this
>    replacement can be applied if any of the following rules hold:
>    
>    1. The relocation type indicates that the address resides within
>    the CodeCache and the necessary patching logic is provided in
>    `fix_relocation_after_move()`.
>    2. The target address is fixed (i.e., does not require relocation)
>    and is within the reachable range for `adrp`.
>    
>    The patch performs the filtering in `is_relocated_within_codecache()`
>    and `is_adrp_reachable()` to ensure this optimization is applied
>    safely and selectively.

src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp line 2272:

> 2270: 
> 2271: #ifdef ASSERT
> 2272: bool MacroAssembler::unqualified_type(relocInfo::relocType rtype) {

Suggestion:

bool MacroAssembler::is_unqualified_type(relocInfo::relocType rtype) {

src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp line 2302:

> 2300:     add(r, r, offset);
> 2301:   } else {
> 2302: #ifdef ASSERT

You don't need this

#ifdef ASSERT

src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp line 5799:

> 5797: }
> 5798: 
> 5799: bool MacroAssembler::is_adrp_reachable(const address target) {

assert here that code cache is 4k-aligned.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/26653#discussion_r2285243434
PR Review Comment: https://git.openjdk.org/jdk/pull/26653#discussion_r2285230901
PR Review Comment: https://git.openjdk.org/jdk/pull/26653#discussion_r2285238274