RFR: 8314078: HotSpotConstantPool.lookupField() asserts due to field changes in ConstantPool.cpp

[Doug Simon]

On Fri, 11 Aug 2023 01:15:01 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> This PR updates Java code in JVMCI to match the C code changes in [JDK-8301996](https://bugs.openjdk.java.net/browse/JDK-8301996) that modified the constant pool layout. Essentially, the indices after a getfield/putfield/getstatic/putstatic bytecode is no longer a CpCacheIndex, but an index for `ConstantPool::resolved_field_entry_at(int field_index)`.
> 
> The assertion (and subsequent crash) happen only in debug builds. Out of pure luck, in product build JVMCI produces the correct output even after [JDK-8301996](https://bugs.openjdk.java.net/browse/JDK-8301996), although the code was doing the wrong thing.
> 
> This PR has (so far) two commits:
> 
> - 6527e67b1832087d180d2b50b65aaeca2e244c28 The actual functional change to use the `rawIndex` that follows a field bytecode.
> - c322b8e71d4d9e33bd065e64420101010f9127fc Fixed incorrectly named parameters and variables in the JVMCI code and JavaDoc. In most cases, `cpi` needs to be changed to `rawIndex` to reflect the correct type of the index.
> 
> To help reviewing, I am limiting the renaming to just those affected by the field changes (without the renames, it's hard to validate that I am actually doing the right thing).
> 
> There are still some cases of `cpi` that need to be changed to `rawIndex`. I will fix those in a separate RFE. E.g. in ConstantPool.java:
> 
> 
> default JavaMethod lookupMethod(int cpi, int opcode) {
>     return lookupMethod(cpi, opcode, null);
> }

Marked as reviewed by dnsimon (Reviewer).

Thanks for doing this Ioi.

In this PR or the follow-up renaming RFE, could you please add a "decoder ring" comment to the javadoc for ConstantPool. An incomplete example:

 * The following terminology is used when indexing a constant pool entry:
 * <ul>
 * <li>rawIndex - index in the bytecode stream after the opcode (could be rewritten for some bytecodes)</li>
 * <li>cpi - the class file constant pool index</li>
 * <li>cpci - a constant pool cache index</li>
 * </ul>

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PR Review: https://git.openjdk.org/jdk/pull/15237#pullrequestreview-1573540144
PR Comment: https://git.openjdk.org/jdk/pull/15237#issuecomment-1674643799