RFR: 8253089: Windows (MSVC 2017) build fails after JDK-8243208

[Ioi Lam]

On Mon, 14 Sep 2020 17:17:27 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> LGTM, Goetz.
>
> I agree with Kim that it's better to disable the warning.

TL/DR; I think the proposed change is acceptable as it doesn't significantly change the bucket size distribution.

====
I added a patch to show the bucket size distribution:
http://cr.openjdk.java.net/~iklam/jdk16/8253089-jvmFlagLookup-u2-msvc/buckets_size.patch.txt

I then apply the proposed change on top. The contents of the hashtable is changed (I don't know why Aleksey sees no
changes; I used output from `gcc -save-temps`). Even the lower 16 bit of the hash may not change, this expression will
give different results depending on the upper 16 bits: int bucket_index = (int)(hash % NUM_BUCKETS); Anyway, the bucket
size distribution is about the same as before. The max bucket size is about 12.

http://cr.openjdk.java.net/~iklam/jdk16/8253089-jvmFlagLookup-u2-msvc/jvmFlagLookup.s.old.txt
http://cr.openjdk.java.net/~iklam/jdk16/8253089-jvmFlagLookup-u2-msvc/jvmFlagLookup.s.new.txt

Scroll down to here: the first 277 entries are the bucket size.

_ZL18_flag_lookup_table:
	.value	2
	.value	8
	.value	3
	.value	5
	.value	10
	.value	1
	.value	7
	.value	8
	.value	3
	.value	3
	.value	5
	.value	2
	.value	5
	.value	7
	.value	6
	.value	2
	.value	5
	.value	2
	.value	6
	.value	3
	.value	8
	.value	1
	.value	3

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PR: https://git.openjdk.java.net/jdk/pull/150