RFR: 8261671: X86 I2L conversion can be skipped for certain masked positive values [v4]

[Marcus G K Williams]

> 8261671: X86 I2L conversion can be skipped for certain masked positive values
> 
> For the following expression:
>  (long)(value & mask)
> Where value is of int type and mask is constant (power of two – 1), we can directly generate bzhi instruction to zero the upper bits instead of doing an andl, followed by movslq
> 
> Before:
> Benchmark Mode Cnt Score Error Units
> SkipIntToLongCast.skipMaskedSmallPositiveCast avgt 15 10.679 ± 1.496 ns/op
> 
> 
> After:
> Benchmark Mode Cnt Score Error Units
> SkipIntToLongCast.skipMaskedSmallPositiveCast avgt 15 7.870 ± 0.067 ns/op
> 
> Signed-off-by: Marcus G K Williams <marcus.williams at intel.com>

Marcus G K Williams has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - Add BMI2 and BzhiTestI2L tests
   
   Signed-off-by: Marcus G K Williams <marcus.williams at intel.com>
 - Merge branch 'master' into int2l_opt
 - Revert to predicate supports_bmi2
   
   Signed-off-by: Marcus G K Williams <marcus.williams at intel.com>
 - Update convI2LAndI_reg_immIbitmask w/ is_Intel
   
   Signed-off-by: Marcus G K Williams <marcus.williams at intel.com>
 - 8261671: Skip unnecessary Int2L conversions
   
   X86 I2L conversion can be skipped for certain
   masked positive values.
   
   Signed-off-by: Marcus G K Williams <marcus.williams at intel.com>

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2590/files
  - new: https://git.openjdk.java.net/jdk/pull/2590/files/2717297b..1a88325b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2590&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2590&range=02-03

  Stats: 31038 lines in 1013 files changed: 19535 ins; 6109 del; 5394 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2590.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2590/head:pull/2590

PR: https://git.openjdk.java.net/jdk/pull/2590