fallback: legalize: G_ASHR <8 x s16>

Run:	main-bc8218b282-20261015-074651
Kind:	fallback
Category:	legalize: G_ASHR <8 x s16>
Occurrences:	6 in 3 configs, 2 test files
Snippet from:	rvp-simd-64.ll @test_paadd_b via llvm-extract
Config:	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
Local check:	reproduces at bc8218b282
Compiler Explorer:	not uploaded (over --godbolt-limit or disabled)

Snippet:

define <8 x i8> @test_paadd_b(<8 x i8> %a, <8 x i8> %b) {
  %ext.a = sext <8 x i8> %a to <8 x i16>
  %ext.b = sext <8 x i8> %b to <8 x i16>
  %add = add nsw <8 x i16> %ext.a, %ext.b
  %shift = ashr <8 x i16> %add, splat (i16 1)
  %res = trunc <8 x i16> %shift to <8 x i8>
  ret <8 x i8> %res
}

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: %7:_(<8 x s16>) = G_ASHR %4:_, %5:_(<8 x s16>) (in function: test_paadd_b)
warning: Instruction selection used fallback path for test_paadd_b

Occurrences (6):

Input	Function	Config
rvp-simd-64.ll	test_paadd_b	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pasub_b	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
smulh.ll	smulh_v8i8	`-mtriple=riscv32 -mattr=+m`
smulh.ll	smulh_v8i8	`-mtriple=riscv64 -mattr=+m`
smulh.7077678c78.ll (mutant of smulh.ll)	smulh_v8i8	`-mtriple=riscv32 -mattr=+m`
smulh.7283c3de45.ll (mutant of smulh.ll)	smulh_v8i8	`-mtriple=riscv64 -mattr=+m`

Generated 2026-10-15 08:05 UTC.