fallback: legalize: G_INSERT_SUBVECTOR <vscale x 2 x s64>,<2 x s64>

Snippet:

declare void @vector_use(<2 x i64>)

; Function Attrs: nounwind
define void @mul_use_commutative_clmul_v2i64(<2 x i64> %x, <2 x i64> %y, ptr %p0, ptr %p1) #0 {
  %xy = call <2 x i64> @llvm.clmul.v2i64(<2 x i64> %x, <2 x i64> %y)
  %yx = call <2 x i64> @llvm.clmul.v2i64(<2 x i64> %y, <2 x i64> %x)
  store <2 x i64> %xy, ptr %p0, align 16
  call void @vector_use(<2 x i64> %xy)
  store <2 x i64> %yx, ptr %p1, align 16
  ret void
}

; Function Attrs: nocallback nocreateundeforpoison nofree nosync nounwind speculatable willreturn memory(none)
declare <2 x i64> @llvm.clmul.v2i64(<2 x i64>, <2 x i64>) #1

attributes #0 = { nounwind }
attributes #1 = { nocallback nocreateundeforpoison nofree nosync nounwind speculatable willreturn memory(none) }

Reproduce:

llc -mtriple=riscv32 -mattr=+m,+zvbc -verify-machineinstrs -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv32 -mattr=+m,+zvbc -verify-machineinstrs -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %9:_(<vscale x 2 x s64>) = G_INSERT_SUBVECTOR %8:_, %6:_(<2 x s64>), 0 (in function: mul_use_commutative_clmul_v2i64)
warning: Instruction selection used fallback path for mul_use_commutative_clmul_v2i64

Occurrences (2):

Generated 2026-10-15 08:05 UTC.