fallback: legalize: G_VECREDUCE_ADD s16,<16 x s16>

Snippet:

define i16 @add_ext_i16(<16 x i8> %a, <16 x i8> %b) {
  %ae = zext <16 x i8> %a to <16 x i16>
  %be = zext <16 x i8> %b to <16 x i16>
  %r1 = call i16 @llvm.vector.reduce.add.v16i16(<16 x i16> %ae)
  %r2 = call i16 @llvm.vector.reduce.add.v16i16(<16 x i16> %be)
  %r = add i16 %r1, %r2
  ret i16 %r
}

; Function Attrs: nocallback nocreateundeforpoison nofree nosync nounwind speculatable willreturn memory(none)
declare i16 @llvm.vector.reduce.add.v16i16(<16 x i16>) #0

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

Reproduce:

llc -mtriple=riscv32 -mattr=+d,+zfh,+zvfh,+v,+m -target-abi=ilp32d -verify-machineinstrs -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv32 -mattr=+d,+zfh,+zvfh,+v,+m -target-abi=ilp32d -verify-machineinstrs -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %7:_(s16) = G_VECREDUCE_ADD %5:_(<16 x s16>) (in function: add_ext_i16)
warning: Instruction selection used fallback path for add_ext_i16

Occurrences (4):

Generated 2026-10-15 08:05 UTC.