[lworld] RFR: 8320225: [lworld] TestBasicFunctionality::test20 fails intermittently because it does not correctly handle coalescing of subword stores

[Tobias Hartmann]

`TestBasicFunctionality::test20` fails intermittently if one of the randomly chosen field values of a value object is zero because that will lead to slightly different type information for the captured stores that initialize the object. 

Passing case:

299  StoreP  === 330 375 285 290  [[ 302 304 ]]  @rawptr:BotPTR, idx=Raw;  Memory: @rawptr:BotPTR, idx=Raw;
304  StoreL  === 330 299 289 302  [[ 308 ]]  @null  Memory: @rawptr:BotPTR, idx=Raw;
308  StoreNKlass  === 330 304 306 331  [[ 316 ]]  @null  Memory: @rawptr:BotPTR, idx=Raw;
316  StoreI  === 330 308 315 57  [[ 280 ]]  @rawptr:BotPTR, idx=Raw;  Memory: @rawptr:BotPTR, idx=Raw;
311  StoreL  === 279 280 309 310  [[ 246 ]]  @rawptr:BotPTR, idx=Raw;  Memory: @rawptr:BotPTR, idx=Raw; !orig=[245],3161 !jvms: MyValue1::<vnew> @ bci:82 (line 57) MyValue1::setV4 @ bci:40 (line 178) MyValue1::createWithFieldsInline @ bci:106 (line 89) TestBasicFunctionality::test20 @ bci:6 (line 475)
246  StoreL  === 279 311 254 188  [[ 314 ]]  @compiler/valhalla/inlinetypes/MyValue2 (compiler/valhalla/inlinetypes/MyInterface):exact+24 *, name=l, idx=11;  Memory: @rawptr:BotPTR, idx=Raw; !orig=3166 !jvms: MyValue1::<vnew> @ bci:82 (line 57) MyValue1::setV4 @ bci:40 (line 178) MyValue1::createWithFieldsInline @ bci:106 (line 89) TestBasicFunctionality::test20 @ bci:6 (line 475)
314  StoreL  === 279 246 312 313  [[ 231 ]]  @rawptr:BotPTR, idx=Raw;  Memory: @rawptr:BotPTR, idx=Raw; !orig=[248],3178 !jvms: MyValue1::<vnew> @ bci:82 (line 57) MyValue1::setV4 @ bci:40 (line 178) MyValue1::createWithFieldsInline @ bci:106 (line 89) TestBasicFunctionality::test20 @ bci:6 (line 475)


Failing case:

300  StoreP  === 337 384 286 291  [[ 303 305 ]]  @rawptr:BotPTR, idx=Raw;  Memory: @rawptr:BotPTR, idx=Raw;
305  StoreL  === 337 300 290 303  [[ 309 ]]  @null  Memory: @rawptr:BotPTR, idx=Raw;
309  StoreNKlass  === 337 305 307 338  [[ 317 ]]  @null  Memory: @rawptr:BotPTR, idx=Raw;
317  StoreI  === 337 309 316 57  [[ 343 ]]  @rawptr:BotPTR, idx=Raw;  Memory: @rawptr:BotPTR, idx=Raw;
343  StoreL  === 337 317 322 184  [[ 281 ]]  @rawptr:BotPTR, idx=Raw;  Memory: @rawptr:BotPTR, idx=Raw; !orig=[323]
312  StoreL  === 280 281 310 311  [[ 315 ]]  @rawptr:BotPTR, idx=Raw;  Memory: @rawptr:BotPTR, idx=Raw; !orig=[248],3163 !jvms: MyValue1::<vnew> @ bci:82 (line 57) MyValue1::setV4 @ bci:40 (line 178) MyValue1::createWithFieldsInline @ bci:106 (line 89) TestBasicFunctionality::test20 @ bci:6 (line 475)
315  StoreL  === 280 312 313 314  [[ 234 ]]  @rawptr:BotPTR, idx=Raw;  Memory: @rawptr:BotPTR, idx=Raw; !orig=[250],3180 !jvms: MyValue1::<vnew> @ bci:82 (line 57) MyValue1::setV4 @ bci:40 (line 178) MyValue1::createWithFieldsInline @ bci:106 (line 89) TestBasicFunctionality::test20 @ bci:6 (line 475)
``` 

In the failing case, the `343  StoreL` is a zeroing store that's separated from the other non-zero `StoreL` by a memory Phi and thus not detected as a store to field `l`. The fix is to make the test more robust by matching on the number of `STORE_L` instead.

Thanks,
Tobias

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

Commit messages:
 - 8320225: [lworld] TestBasicFunctionality::test20 fails intermittently because it does not correctly handle coalescing of subword stores

Changes: https://git.openjdk.org/valhalla/pull/957/files
 Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=957&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320225
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/valhalla/pull/957.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/957/head:pull/957

PR: https://git.openjdk.org/valhalla/pull/957