RFR: 8339205: Optimize StackMapGenerator [v7]

[Shaojin Wen]

> Reduce code size by combining calls and defining local variables

Shaojin Wen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 18 commits:

 - Merge remote-tracking branch 'upstream/master' into optim_stack_map_gen_202408
 - use 4 spaces.
 - Update src/java.base/share/classes/jdk/internal/classfile/impl/StackMapGenerator.java
   
   Co-authored-by: Chen Liang <liach at openjdk.org>
 - Merge branch 'master' into optim_stack_map_gen_202408
 - Merge branch 'master' into optim_stack_map_gen_202408
 - reduce codeSize
 - reduce codeSize
 - decStack & stackUnderflow
 - fix merge error
 - Merge branch 'master' into optim_stack_map_gen_202408
 - ... and 8 more: https://git.openjdk.org/jdk/compare/3ab519f1...248f7474

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

Changes: https://git.openjdk.org/jdk/pull/20756/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20756&range=06
  Stats: 342 lines in 1 file changed: 217 ins; 33 del; 92 mod
  Patch: https://git.openjdk.org/jdk/pull/20756.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20756/head:pull/20756

PR: https://git.openjdk.org/jdk/pull/20756