Pad with a mix of bytes and longs

[cl4es]

Using a mix of bytes and longs we should get the gap-filling effect described in https://shipilev.net/jvm/objects-inside-out/#_observation_hierarchy_tower_padding_trick_collapse_in_jdk_15 while reducing size of generated code by roughly 20%:

864772  jmh-samples/target/jmh-samples-1.38-SNAPSHOT.jar
490531  jmh-samples/target/jmh-samples-1.38-SNAPSHOT-sources.jar

684383 jmh-samples/target/jmh-samples-1.38-SNAPSHOT.jar
399758 jmh-samples/target/jmh-samples-1.38-SNAPSHOT-sources.jar

---

Progress

• Change must not contain extraneous whitespace
• Change must be properly reviewed (1 review required, with at least 1 Committer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jmh.git pull/147/head:pull/147
$ git checkout pull/147

Update a local copy of the PR:
$ git checkout pull/147
$ git pull https://git.openjdk.org/jmh.git pull/147/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 147

View PR using the GUI difftool:
$ git pr show -t 147

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jmh/pull/147.diff

[bridgekeeper]

👋 Welcome back redestad! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[cl4es]

Checking locally with JOL internals on my M1 the B2 fields are laid out at the exact same offset (280), only discernible difference is that byte and long padding fields of the B1 type are laid out in reverse:

240   8             long JMHSample_39_MemoryAccess_jmhType_B1.b1_2b                  0
248   8             long JMHSample_39_MemoryAccess_jmhType_B1.b1_2c                  0
256   8             long JMHSample_39_MemoryAccess_jmhType_B1.b1_2d                  0
264   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_00                  0
265   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_01                  0
266   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_02                  0
267   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_03                  0
268   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_04                  0
269   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_05                  0
270   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_06                  0
271   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_07                  0
272   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_08                  0
273   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_09                  0
274   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_0a                  0
275   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_0b                  0
276   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_0c                  0
277   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_0d                  0
278   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_0e                  0
279   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_0f                  0
280   4              int JMHSample_39_MemoryAccess_jmhType_B2.setupTrialMutex        0
284   4              int JMHSample_39_MemoryAccess_jmhType_B2.tearTrialMutex         0
288   4              int JMHSample_39_MemoryAccess_jmhType_B2.setupIterationMutex    0
292   4              int JMHSample_39_MemoryAccess_jmhType_B2.tearIterationMutex     0
296   4              int JMHSample_39_MemoryAccess_jmhType_B2.setupInvocationMutex   0
300   4              int JMHSample_39_MemoryAccess_jmhType_B2.tearInvocationMutex    0
304   1          boolean JMHSample_39_MemoryAccess_jmhType_B2.readyTrial             false
305   1          boolean JMHSample_39_MemoryAccess_jmhType_B2.readyIteration         false
306   1          boolean JMHSample_39_MemoryAccess_jmhType_B2.readyInvocation        false
307   1             byte JMHSample_39_MemoryAccess_jmhType.b3_00                     0
308   1             byte JMHSample_39_MemoryAccess_jmhType.b3_01                     0
309   1             byte JMHSample_39_MemoryAccess_jmhType.b3_02                     0
310   1             byte JMHSample_39_MemoryAccess_jmhType.b3_03                     0
311   1             byte JMHSample_39_MemoryAccess_jmhType.b3_04                     0

Before:

276   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_252                 0
277   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_253                 0
278   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_254                 0
279   1             byte JMHSample_39_MemoryAccess_jmhType_B1.b1_255                 0
280   4              int JMHSample_39_MemoryAccess_jmhType_B2.setupTrialMutex        0
284   4              int JMHSample_39_MemoryAccess_jmhType_B2.tearTrialMutex         0
288   4              int JMHSample_39_MemoryAccess_jmhType_B2.setupIterationMutex    0
292   4              int JMHSample_39_MemoryAccess_jmhType_B2.tearIterationMutex     0
296   4              int JMHSample_39_MemoryAccess_jmhType_B2.setupInvocationMutex   0
300   4              int JMHSample_39_MemoryAccess_jmhType_B2.tearInvocationMutex    0
304   1          boolean JMHSample_39_MemoryAccess_jmhType_B2.readyTrial             false
305   1          boolean JMHSample_39_MemoryAccess_jmhType_B2.readyIteration         false
306   1          boolean JMHSample_39_MemoryAccess_jmhType_B2.readyInvocation        false
307   1             byte JMHSample_39_MemoryAccess_jmhType.b3_000                    0
308   1             byte JMHSample_39_MemoryAccess_jmhType.b3_001                    0
309   1             byte JMHSample_39_MemoryAccess_jmhType.b3_002                    0
310   1             byte JMHSample_39_MemoryAccess_jmhType.b3_003                    0

Note: while using hexadecimal has a size benefit, I just thought it made it easier to check that the generated code is correct since everything aligns when doing 16 vars per line, e.g.:

    byte p00, p01, p02, p03, p04, p05, p06, p07, p08, p09, p0a, p0b, p0c, p0d, p0e, p0f;
    long p10, p11, p12, p13, p14, p15, p16, p17, p18, p19, p1a, p1b, p1c, p1d, p1e, p1f;
    long p20, p21, p22, p23, p24, p25, p26, p27, p28, p29, p2a, p2b, p2c, p2d;