fallback: legalize: G_INSERT_VECTOR_ELT <4 x s8>,s8,s64

Run:main-bc8218b282-20261015-074651
Kind:fallback
Category:legalize: G_INSERT_VECTOR_ELT <4 x s8>,s8,s64 NEW
Occurrences:1 in 1 configs, 1 test files
Snippet from:rvp-insert-subvector.b55629cbe8.ll (mutant of rvp-insert-subvector.ll) @insert_zero_v4i8 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:

@G = external global i8
@G.1 = external global <4 x i8>

define <8 x i8> @insert_zero_v4i8(<4 x i8> %v) {
  %LGV = load i8, ptr @G, align 1
  %r = call <8 x i8> @llvm.vector.insert.v8i8.v4i8(<8 x i8> zeroinitializer, <4 x i8> %v, i64 0)
  %I = insertelement <4 x i8> %v, i8 %LGV, i16 0
  store <4 x i8> %I, ptr @G.1, align 4
  ret <8 x i8> %r
}

; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare <8 x i8> @llvm.vector.insert.v8i8.v4i8(<8 x i8>, <4 x i8>, 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: %8:_(<4 x s8>) = G_INSERT_VECTOR_ELT %0:_, %3:_(s8), %9:_(s64) (in function: insert_zero_v4i8)
warning: Instruction selection used fallback path for insert_zero_v4i8

Occurrences (1):

InputFunctionConfig
rvp-insert-subvector.b55629cbe8.ll (mutant of rvp-insert-subvector.ll)insert_zero_v4i8-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs

Generated 2026-10-15 08:05 UTC.