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

Snippet:

define <4 x i16> @insert_zero_v2i16(<2 x i16> %v) {
  %r = call <4 x i16> @llvm.vector.insert.v4i16.v2i16(<4 x i16> zeroinitializer, <2 x i16> %v, i64 0)
  ret <4 x i16> %r
}

; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare <4 x i16> @llvm.vector.insert.v4i16.v2i16(<4 x i16>, <2 x i16>, i64 immarg) #0

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

Reproduce:

llc -mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %3:_(<4 x s16>) = G_INSERT_SUBVECTOR %4:_, %0:_(<2 x s16>), 0 (in function: insert_zero_v2i16)
warning: Instruction selection used fallback path for insert_zero_v2i16

Occurrences (3):

Generated 2026-10-15 08:05 UTC.