Remove vmSnapshotFilePath from J9SpecialArguments

[ThanHenderson]

Signed-off-by: Nathan Henderson [email protected]

[babsingh]

While this approach does save on an intermediary pointer, it requires an additional iteration through the args list. In the worst case, depending on the location of the -Xsnapshot= option and the size of the list, it may result in a full traversal of a potentially large args list, which could negatively impact startup performance. Although this incurs additional memory usage, the impact on startup time outweighs the benefit of reduced memory usage. @tajila Thoughts?

[ThanHenderson]

Removing the additional memory that a pointer takes up wasn't the main thrust behind this; it is more so a code cleanliness patch.

I understand that ideally we would not traverse the args list again in its entirety, but VMOPT_XSNAPSHOT has little overlap with other options, so the strncmp would be short circuited relatively quickly (at most 4 bytes are being compared per non-matching arg that is specified after VMOPT_XSNAPSHOT i.e. with VMOPT_XSNW).

To get around this, we could also pass createParams into initialArgumentScan. I had avoided this approach because the parameter would be unused within the function when J9VM_OPT_SNAPSHOTS code isn't defined. I guess I could just guard the function parameter too though. I've pushed a second commit that implements this version.

[ThanHenderson]

Actually, we could just change the initialArgumentScan signature to:
initialArgumentScan(JavaVMInitArgs *args, J9SpecialArguments *specialArgs, J9CreateJavaVMParams *createParams)
regardless of whether J9VM_OPT_SNAPSHOT code is generated, and just set the localVerboseLevel in that function rather than outside of it like it is done now:

openj9/runtime/j9vm/jvm.c

Lines 2246 to 2250 in dc42c9a

	localVerboseLevel = specialArgs.localVerboseLevel;
	if (VERBOSE_INIT == localVerboseLevel) {
	createParams.flags |= J9_CREATEJAVAVM_VERBOSE_INIT;
	}

[babsingh]

jenkins test sanity.functional amac jdk21

[babsingh]

The PR builds will test the changes in the disabled state. @ThanHenderson Did you test these changes in the enabled state; do they look good?

[ThanHenderson]

Yes, I have tested it. All good.