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

[Fei Yang]

On Mon, 9 Sep 2024 11:17:54 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

> 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.

Nice catch! Thanks Robbin. I am trying it on my machines. BTW: Seems this fix deserves a small code comment.

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PR Review: https://git.openjdk.org/jdk/pull/20912#pullrequestreview-2290174737