The test compiler/floatingpoint/ScalarFPtoIntCastTest.java enforces x86 specific IR on non-x86 platforms if the feature `avx10_2` is not available.

The test succeeds coincidentally on aarch64 and riscv because they have instruction forms with the same names as on x86 in their AD files.

Example double2byte
https://github.com/openjdk/jdk/blob/fdbba049a2491c591fc1a866e4707bf9aac50f17/test/hotspot/jtreg/compiler/floatingpoint/ScalarFPtoIntCastTest.java#L193-L206

The test double2byte expects at least one IRNode.X86_SCONV_D2I if the feature `avx10_2` is not available.
(https://github.com/openjdk/jdk/blob/fdbba049a2491c591fc1a866e4707bf9aac50f17/test/hotspot/jtreg/compiler/floatingpoint/ScalarFPtoIntCastTest.java#L195-L196)

IRNode.X86_SCONV_D2I is defined as "convD2I_reg_reg"
(https://github.com/openjdk/jdk/blob/fdbba049a2491c591fc1a866e4707bf9aac50f17/test/hotspot/jtreg/compiler/lib/ir_framework/IRNode.java#L2700C43-L2700C58)

Coincidentally the instruction forms on aarch64 and riscv are also named "convD2I_reg_reg". That's why double2byte succeeds on these platforms.
It fails though on ppc64 because the corresponding instruction forms on ppc64 have different names.