RFR: 8339741: RISC-V: C ABI breakage for integer on stack

[Robbin Ehn]

Hi please review,

When calling a native function using integers smaller than 64,
they must be loaded from a Java stack slot and widen to 64-bit, sign-extended.
In the interpreter case we only store 32-bit, which means the top 32-bit are 'random'.
In the compiler case we do an ld and grab random top 32-bit.
These should be loaded with a lw from Java stack, thus proper sign extended and then stored with sd into the native stack.

I found the intrepter bug first, wrote a test case for it, which found the compiler bug.

Here you can see the difference, both are legal todo from a compiler:
https://godbolt.org/z/85aMhja5f
Relevant specs:
https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-cc.adoc
> integer scalars narrower than XLEN bits are widened according to the sign of their type up to 32 bits, then sign-extended to XLEN bits.

I checked floats also, they seems fine, but please go ahead and do a check regarding floats.

Passes ./test/hotspot/jtreg/compiler/calls/, runnnig t1.

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Commit messages:
 - Fixed

Changes: https://git.openjdk.org/jdk/pull/20912/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20912&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339741
  Stats: 136 lines in 4 files changed: 134 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/20912.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20912/head:pull/20912

PR: https://git.openjdk.org/jdk/pull/20912