fallback: legalize: G_INSERT_SUBVECTOR <vscale x 4 x s8>,<8 x s8>

Snippet:

@G = external global i1

; Function Attrs: nounwind
define <8 x i8> @smulh_v8i8(<8 x i8> %x, <8 x i8> %y) #0 {
  %LGV = load i1, ptr @G, align 1
  %r = call <8 x i8> @llvm.smulh.v8i8(<8 x i8> %x, <8 x i8> %y)
  br i1 %LGV, label %T, label %F

BB:                                               ; preds = %F, %T
  ret <8 x i8> %r

T:                                                ; preds = %0
  br label %BB

F:                                                ; preds = %0
  br label %BB
}

; Function Attrs: nocallback nocreateundeforpoison nofree nosync nounwind speculatable willreturn memory(none)
declare <8 x i8> @llvm.smulh.v8i8(<8 x i8>, <8 x i8>) #1

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

Reproduce:

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

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %6:_(<vscale x 4 x s8>) = G_INSERT_SUBVECTOR %5:_, %4:_(<8 x s8>), 0 (in function: smulh_v8i8)
warning: Instruction selection used fallback path for smulh_v8i8

Occurrences (4):

Generated 2026-10-15 08:05 UTC.