fallback: legalize: G_SHUFFLE

fallback: legalize: G_SHUFFLE_VECTOR <8 x s8>

Run:	explore-bc8218b282-20261015-075519
Kind:	fallback
Category:	legalize: G_SHUFFLE_VECTOR <8 x s8>
Occurrences:	22 in 1 configs, 4 test files
Snippet from:	rvp-reverse.ll @test_prev_v8i8 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_prev_v8i8(<8 x i8> %a) {
  %r = shufflevector <8 x i8> %a, <8 x i8> poison, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
  ret <8 x i8> %r
}

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: %1:_(<8 x s8>) = G_SHUFFLE_VECTOR %0:_(<8 x s8>), %2:_, shufflemask(7, 6, 5, 4, 3, 2, 1, 0) (in function: test_prev_v8i8)
warning: Instruction selection used fallback path for test_prev_v8i8

Occurrences (22):

Input	Function	Config
rvp-narrowing-zip.ll	test_pnzip_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-narrowing-zip.ll	test_pnziph_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-reverse.ll	test_prev_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_ppaireo_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_ppairoe_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_ppaire_swapped_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_ppairo_swapped_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_ppaireo_swapped_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_ppairoe_swapped_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_ppair_v1_used_twice_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_ppair_v2_used_twice_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pslide1up_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-simd-64.ll	test_pslide1down_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-zip.ll	test_unzip8p_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-zip.ll	test_unzip8hp_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-zip.ll	test_unzip8p_v8i8_partial_poison	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-zip.ll	test_unzip8hp_v8i8_partial_poison	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-narrowing-zip.54b004892c.ll (mutant of rvp-narrowing-zip.ll)	test_pnziph_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-narrowing-zip.92e5c0a676.ll (mutant of rvp-narrowing-zip.ll)	test_pnziph_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-reverse.552ba0edff.ll (mutant of rvp-reverse.ll)	test_prev_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-zip.10d4a4bde6.ll (mutant of rvp-zip.ll)	test_unzip8hp_v8i8_partial_poison	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`
rvp-zip.a312104e68.ll (mutant of rvp-zip.ll)	test_unzip8p_v8i8	`-mtriple=riscv64 -mattr=+experimental-p,+m,+zbb -verify-machineinstrs`

Generated 2026-10-15 08:05 UTC.