fallback: legalize: G_INSERT_SUBVECTOR <vscale x 2 x s16>,<4 x s16>

Snippet:

@G.4 = external global <4 x i16>

; Function Attrs: nounwind
define <4 x i16> @smulh_v4i16(<4 x i16> %x, <4 x i16> %y) #0 {
  %S = shufflevector <4 x i16> %y, <4 x i16> %x, <4 x i32> poison
  %r = call <4 x i16> @llvm.smulh.v4i16(<4 x i16> %x, <4 x i16> %y)
  store <4 x i16> %S, ptr @G.4, align 8
  ret <4 x i16> %r
}

; Function Attrs: nocallback nocreateundeforpoison nofree nosync nounwind speculatable willreturn memory(none)
declare <4 x i16> @llvm.smulh.v4i16(<4 x i16>, <4 x i16>) #1

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

Reproduce:

llc -mtriple=riscv64 -mattr=+m,+v -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv64 -mattr=+m,+v -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %12:_(<vscale x 2 x s16>) = G_INSERT_SUBVECTOR %11:_, %4:_(<4 x s16>), 0 (in function: smulh_v4i16)
warning: Instruction selection used fallback path for smulh_v4i16

Occurrences (4):

Generated 2026-10-15 08:05 UTC.