RFR: 8357220: Introduce a BSMAttributeEntry struct

[Lois Foltan]

On Mon, 19 May 2025 07:35:16 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

> Hi,
> 
>  The constant pool currently has a lot of methods specific to extracting parts of the operands array. What this array actually is, is a sequence of bootstrap method attribute entries, where each entry has the following components:
> 
> ```c++
> struct BSMAE {
>   u2 bootstrap_method_index;
>   u2 argument_count;
>   u2 arguments[argument_count];
> }
> 
> 
> We can removes some of these operands array specific methods, and instead allows you to extract BSMAttributeEntrys which you can then use to extract its piece wise components. This makes for a nicer interface, and a bit easier to come into as a reader of the code, as it more closely mirrors the JVMS. 
> 
> Please consider!
> 
> Testing: Currently GHA, running tier1-tier3

Overall looks good, a couple of comments below.

src/hotspot/share/oops/constantPool.hpp line 80:

> 78: };
> 79: 
> 80: class BSMAttributeEntry {

Please consider moving the description comment from lines #569-#572 ahead of this structure

src/hotspot/share/oops/constantPool.hpp line 92:

> 90:     return reinterpret_cast<u2*>(this + 1);
> 91:   }
> 92: 

Remove blank lines at #92, #95, #103

src/hotspot/share/oops/constantPool.hpp line 105:

> 103: 
> 104:   int argument_index(int n) const {
> 105:     assert(checked_cast<u2>(n) < _argument_count, "oob");

Should the assert contain a check that _argument_count is >= 0 as well?

src/hotspot/share/oops/constantPool.hpp line 638:

> 636:   u2 bootstrap_argument_count_at(int cp_index) {
> 637:     assert(tag_at(cp_index).has_bootstrap(), "Corrupted constant pool");
> 638:     int bsmai = bootstrap_methods_attribute_index(cp_index);

The "matched ending" assert was the only code that used bootstrap_operand_limit(), so that method could be removed as well.  This comment applies to bootstrap_operand_base() as well.

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/ConstantPool.java line 124:

> 122:   private static long elementSize;
> 123: 
> 124:   private static int INDY_BSM_OFFSET = 0;

Please update the copyright of this file.

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

PR Review: https://git.openjdk.org/jdk/pull/25298#pullrequestreview-2858597040
PR Review Comment: https://git.openjdk.org/jdk/pull/25298#discussion_r2100820121
PR Review Comment: https://git.openjdk.org/jdk/pull/25298#discussion_r2100820521
PR Review Comment: https://git.openjdk.org/jdk/pull/25298#discussion_r2100831579
PR Review Comment: https://git.openjdk.org/jdk/pull/25298#discussion_r2100833066
PR Review Comment: https://git.openjdk.org/jdk/pull/25298#discussion_r2100849208