RFR: 8367692: RISC-V: Align post call nop [v5]

[Hamlin Li]

On Thu, 25 Sep 2025 12:44:01 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> Hi please, consider.
>> 
>> As ziccif require instructions to natural aligned to be atomic the 4 byte post call nop must be aligned.
>> But I don't want to add a c.nop(2b) to align the nop(4b) which means the jal(r) must also be algined.
>> As we have no utility to aligned the end of an instruction sequence the call it self is aligned and uses only 4 byte instructions. Only in the case where we could use an two c-instruction we may loose space.
>> 
>> Thanks, Robbin
>
> Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use relocation spec as marker.

src/hotspot/cpu/riscv/c1_LIRAssembler_riscv.cpp line 1353:

> 1351: 
> 1352: void LIR_Assembler::call(LIR_OpJavaCall* op, relocInfo::relocType rtype) {
> 1353:   Assembler::IncompressibleScope scope(_masm);

Is an alignment needed here?

src/hotspot/cpu/riscv/c1_LIRAssembler_riscv.cpp line 1364:

> 1362: 
> 1363: void LIR_Assembler::ic_call(LIR_OpJavaCall* op) {
> 1364:   Assembler::IncompressibleScope scope(_masm);

Is an alignment needed here?

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PR Review Comment: https://git.openjdk.org/jdk/pull/27467#discussion_r2382427866
PR Review Comment: https://git.openjdk.org/jdk/pull/27467#discussion_r2382428132