fallback: legalize: G_ASHR <2 x s256>

Run:explore-bc8218b282-20261015-075519
Kind:fallback
Category:legalize: G_ASHR <2 x s256>
Occurrences:4 in 2 configs, 1 test files
Snippet from:smulh.ll @smulh_v2i128 via llvm-extract
Config:-mtriple=riscv32 -mattr=+m
Local check:reproduces at bc8218b282
Compiler Explorer:not uploaded (over --godbolt-limit or disabled)

Snippet:

; Function Attrs: nounwind
define <2 x i128> @smulh_v2i128(<2 x i128> %x, <2 x i128> %y) #0 {
  %r = call <2 x i128> @llvm.smulh.v2i128(<2 x i128> %x, <2 x i128> %y)
  ret <2 x i128> %r
}

; Function Attrs: nocallback nocreateundeforpoison nofree nosync nounwind speculatable willreturn memory(none)
declare <2 x i128> @llvm.smulh.v2i128(<2 x i128>, <2 x i128>) #1

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

Reproduce:

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

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %32:_(<2 x s256>) = G_ASHR %29:_, %31:_(<2 x s256>) (in function: smulh_v2i128)
warning: Instruction selection used fallback path for smulh_v2i128

Occurrences (4):

InputFunctionConfig
smulh.llsmulh_v2i128-mtriple=riscv32 -mattr=+m
smulh.llsmulh_v2i128-mtriple=riscv64 -mattr=+m
smulh.68ff7ba2dc.ll (mutant of smulh.ll)smulh_v2i128-mtriple=riscv64 -mattr=+m
smulh.7d6a59e58c.ll (mutant of smulh.ll)smulh_v2i128-mtriple=riscv32 -mattr=+m

Generated 2026-10-15 08:05 UTC.