RFR: 8315771: [JVMCI] Resolution of bootstrap methods with int[] static arguments [v8]

[Doug Simon]

On Wed, 13 Sep 2023 15:01:34 GMT, Sacha Coppey <duke at openjdk.org> wrote:

>> Currently, `jdk.vm.ci.meta.ConstantPool.lookupBootstrapMethodInvocation` does not support static arguments of type `int[]`.
>> 
>> Supporting those static arguments allows to correctly lookup the `BootstrapMethodInvocation` of some `InvokeDynamic` and `DynamicConstant`.
>> 
>> To lookup the constant at the index in the static arguments index list, a new class is introduced, allowing to lazily resolve the constant or obtain the constant pool index of the arguments:
>> 
>> 
>>     static class CachedBSMArgs extends AbstractList<JavaConstant> {
>>         private final JavaConstant[] cache;
>>         private final HotSpotConstantPool cp;
>>         private final int bssIndex;
>> 
>>         CachedBSMArgs(HotSpotConstantPool cp, int bssIndex, int size) {
>>             this.cp = cp;
>>             this.bssIndex = bssIndex;
>>             this.cache = new JavaConstant[size];
>>         }
>> 
>>         @Override
>>         public JavaConstant get(int index) {
>>             JavaConstant res = cache[index];
>>             if (res == null) {
>>                 int argCpi = compilerToVM().bootstrapArgumentIndexAt(cp, bssIndex, index);
>>                 res = compilerToVM().lookupConstantInPool(cp, argCpi, false);
>>                 if (res == null) {
>>                     res = JavaConstant.forInt(argCpi);
>>                 }
>>                 cache[index] = res;
>>             }
>>             return res;
>>         }
>> 
>>         @Override
>>         public int size() {
>>             return cache.length;
>>         }
>>     }
>
> Sacha Coppey has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add undefined behavior documentation for bootstrapArgumentIndexAt and update documentation for @return of CachedBSMArgs.get

Please update `test/hotspot/jtreg/compiler/jvmci/jdk.vm.ci.hotspot.test/src/jdk/vm/ci/hotspot/test/TestDynamicConstant.java` to test the new functionality.

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/meta/ConstantPool.java line 172:

> 170:          *
> 171:          * <pre>
> 172:          * lookupConstant(int index, boolean resolve) {

This example should focus on resolving the static arguments:

List<JavaConstant> args = cp.getStaticArguments();
List<JavaConstant> resolvedArgs = new ArrayList<>(args.size());
for (JavaConstant c : args) {
    JavaConstant r = c;
    if (c instanceof PrimitiveConstant pc) {
        r = ...
    }
    resolvedArgs.append(rc);
}

It should also use real Java code to remove all ambiguity.

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

PR Comment: https://git.openjdk.org/jdk/pull/15588#issuecomment-1718890016
PR Review Comment: https://git.openjdk.org/jdk/pull/15588#discussion_r1325465891