RFR: 8292694: x86_64 c2i/i2c adapters may use more stack space than necessary [v2]

[Dean Long]

> The c2i adapter includes the return address in the alignment calculation, making %rsp always mis-aligned according to the ABI.
> 
> The i2c adapter aligns "extrawords" even though %rsp is aligned later, and the incoming stack is not guaranteed to be aligned.

Dean Long has updated the pull request incrementally with one additional commit since the last revision:

  revert change to generate_Continuation_doYield_entry

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10034/files
  - new: https://git.openjdk.org/jdk/pull/10034/files/d6a27a77..30a65c8a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10034&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10034&range=00-01

  Stats: 7 lines in 1 file changed: 0 ins; 7 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10034.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10034/head:pull/10034

PR: https://git.openjdk.org/jdk/pull/10034