<i18n dev> RFR: 8335252: Use ImmutableBitSetPredicate optimize j.u.Formatter.Conversion#isValid

[Shaojin Wen]

On Thu, 27 Jun 2024 11:14:30 GMT, Shaojin Wen <duke at openjdk.org> wrote:

> Currently, the java.util.Formatter$Conversion::isValid method is implemented based on switch, which cannot be inlined because codeSize > 325. This problem can be avoided by implementing it with ImmutableBitSetPredicate.
> 
> use `-XX:+UnlockDiagnosticVMOptions -XX:+PrintInlining` to see the master branch:
> 
> @ 109   java.util.Formatter$Conversion::isValid (358 bytes)   failed to inline: hot method too big
> 
> 
> current version
> 
> @ 109   java.util.Formatter$Conversion::isValid (10 bytes)   inline (hot)
>   @ 4   jdk.internal.util.ImmutableBitSetPredicate$SmallImmutableBitSetPredicate::test (50 bytes)   inline (hot)

@cl4es This is a scenario optimized using ImmutableBitSetPredicate

Execute the following command, we can see that the `java.util.Formatter$Conversion.isValid` method generates a tableswitch of size 85. This large tableswitch makes the code size 358 bytes. Can C2 be optimized to use `jdk.internal.util.ImmutableBitSetPredicate$SmallImmutableBitSetPredicate`?


javap -c java.util.Formatter.Conversion


* byte codes of `Conversion.isValid`

static boolean isValid(char);
    Code:
       0: iload_0
       1: tableswitch   { // 37 to 120
                    37: 352
                    38: 356
                    39: 356
                    40: 356
                    41: 356
                    42: 356
                    43: 356
                    44: 356
                    45: 356
                    46: 356
                    47: 356
                    48: 356
                    49: 356
                    50: 356
                    51: 356
                    52: 356
                    53: 356
                    54: 356
                    55: 356
                    56: 356
                    57: 356
                    58: 356
                    59: 356
                    60: 356
                    61: 356
                    62: 356
                    63: 356
                    64: 356
                    65: 352
                    66: 352
                    67: 352
                    68: 356
                    69: 352
                    70: 356
                    71: 352
                    72: 352
                    73: 356
                    74: 356
                    75: 356
                    76: 356
                    77: 356
                    78: 356
                    79: 356
                    80: 356
                    81: 356
                    82: 356
                    83: 352
                    84: 356
                    85: 356
                    86: 356
                    87: 356
                    88: 352
                    89: 356
                    90: 356
                    91: 356
                    92: 356
                    93: 356
                    94: 356
                    95: 356
                    96: 356
                    97: 352
                    98: 352
                    99: 352
                   100: 352
                   101: 352
                   102: 352
                   103: 352
                   104: 352
                   105: 356
                   106: 356
                   107: 356
                   108: 356
                   109: 356
                   110: 352
                   111: 352
                   112: 356
                   113: 356
                   114: 356
                   115: 352
                   116: 356
                   117: 356
                   118: 356
                   119: 356
                   120: 352
               default: 356
          }
     352: iconst_1
     353: goto          357
     356: iconst_0
     357: ireturn

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

PR Comment: https://git.openjdk.org/jdk/pull/19926#issuecomment-2194416329
PR Comment: https://git.openjdk.org/jdk/pull/19926#issuecomment-2194470276