RFR: 8302114: RISC-V: Several foreign jtreg tests fail with debug build after JDK-8301818

[Feilong Jiang]

This problem only triggers when using debug build to run foreign jtreg tests.
[JDK-8301818](https://bugs.openjdk.org/browse/JDK-8301818) made following code changes in function generate_generic_copy [1]:


    // At this point, it is known to be a typeArray (array_tag 0x3).
 #ifdef ASSERT
     {
       BLOCK_COMMENT("assert primitive array {");
       Label L;
-      __ mvw(t1, Klass::_lh_array_tag_type_value << Klass::_lh_array_tag_shift);
+      __ mv(t1, Klass::_lh_array_tag_type_value << Klass::_lh_array_tag_shift);
       __ bge(lh, t1, L);
       __ stop("must be a primitive array");
       __ bind(L);
       BLOCK_COMMENT("} assert primitive array done");
    }
 #endif


Notably, `Klass::_lh_array_tag_type_value` is of type `unsigned int`:

  static const unsigned int _lh_array_tag_type_value = 0Xffffffff;
  static const int _lh_array_tag_shift = BitsPerInt - _lh_array_tag_bits;
  static const int _lh_array_tag_bits = 2;

So `Klass::_lh_array_tag_type_value << Klass::_lh_array_tag_shift` would be `0xc0000000` of type `unsigned int`.

Previously, `mvw` function would sign-extend this value into 64-bit `0xffffffffc0000000` since we want to do 64-bit signed compare and branch with `bge` instruction next.

  template<typename T, ENABLE_IF(std::is_integral<T>::value)>
  inline void mv(Register Rd, T o) { li(Rd, (int64_t)o); }

  inline void mvw(Register Rd, int32_t imm32) { mv(Rd, imm32); }


But this is not the case when changed to use `mv` with type `unsigned int`. So I think this changes the behaviour.
A simple fix would be adding an explicit int32_t type conversion here for this value, like:

__ mv(t1, (int32_t)(Klass::_lh_array_tag_type_value << Klass::_lh_array_tag_shift));



P.S.: We also checked other places where moving an immediate into registers and some type conversions were added/removed.


[1] https://github.com/openjdk/jdk/commit/c04a982eb47170f3c613617179fca012bb4d40ae

Testing:
- [x] jdk_foreign all passed on Unmatched board (fastdebug build)
- [ ] tier1-3 on Unmatched board (release build)

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

Commit messages:
 - fix move with type conversion

Changes: https://git.openjdk.org/jdk/pull/12481/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12481&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302114
  Stats: 11 lines in 4 files changed: 0 ins; 0 del; 11 mod
  Patch: https://git.openjdk.org/jdk/pull/12481.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12481/head:pull/12481

PR: https://git.openjdk.org/jdk/pull/12481