RFR: 8265403: consolidate definition of CPU features

[Doug Simon]

On Sat, 17 Apr 2021 20:18:31 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

> While porting [JDK-8224974](https://bugs.openjdk.java.net/browse/JDK-8224974) to Graal, I noticed that new CPU features were defined for x86 and AArch64 without being exposed via JVMCI. To avoid this problem in future, this PR updates x86 and AArch64 to define CPU features with a single macro that is used to generate enum declarations as well as vmstructs entries.
> 
> In addition, the JVMCI API is updated to exposes the new CPU feature constants and now has a check that ensure these constants are in sync with the underlying macro definition.

src/hotspot/cpu/aarch64/vm_version_aarch64.cpp line 198:

> 196:   sprintf(buf, "0x%02x:0x%x:0x%03x:%d", _cpu, _variant, _model, _revision);
> 197:   if (_model2) sprintf(buf+strlen(buf), "(0x%03x)", _model2);
> 198: #define ADD_FEATURE_IF_SUPPORTED(id, name, bit) if (_features & CPU_##id) strcat(buf, ", " name);

I'm not sure why only some of the supported AArch64 CPU features were being added to `_features_string` but I assume there's no harm in adding them all.

src/hotspot/cpu/x86/vm_version_x86.hpp line 382:

> 380:   static const char* _features_names[];
> 381: 
> 382:   // NB! When adding new CPU feature detection consider updating vmStructs_x86.hpp, vmStructs_jvmci.hpp, and VM_Version::get_processor_features().

No need for this comment any more as the derivative declarations are now automatically kept up to date.

src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot.amd64/src/jdk/vm/ci/hotspot/amd64/AMD64HotSpotJVMCIBackendFactory.java line 57:

> 55: 
> 56:         Map<String, Long> constants = config.getStore().getConstants();
> 57:         Function<String, CPUFeature> nameToFeature = name -> name.equals("3DNOW_PREFETCH") ? CPUFeature.AMD_3DNOW_PREFETCH : CPUFeature.valueOf(name);

The `AMD_3DNOW_PREFETCH` enum constant has to keep its old name to preserve backward compatibility.

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PR: https://git.openjdk.java.net/jdk/pull/3558