fallback: legalize: G_INSERT_VECTOR

fallback: legalize: G_INSERT_VECTOR_ELT <8 x s8>,s8,s32

Run:	main-04ca53e65f-20261014-113325
Kind:	fallback
Category:	legalize: G_INSERT_VECTOR_ELT <8 x s8>,s8,s32 NEW
Occurrences:	13 in 13 configs, 7 test files
Snippet from:	half-imm.1ed18322c7.ll (mutant of half-imm.ll) @poison via llvm-extract + llvm-reduce
Config:	`-mtriple=riscv32 -mattr=+zhinxmin -verify-machineinstrs -target-abi ilp32`
Local check:	reproduces at 04ca53e65f
Compiler Explorer:	https://godbolt.org/z/rxxKvPE79 (llc-assertions-trunk, checked 2026-10-14 11:04 UTC): G reproduces

Snippet:

define <8 x i8> @poison(<8 x i8> %LGV) {
  %I = insertelement <8 x i8> %LGV, i8 0, i64 0
  ret <8 x i8> %I
}

Compiler Explorer panes:

Pane	Options	Exit	Insts	stderr
GlobalISel	`-mtriple=riscv32 -mattr=+zhinxmin -verify-machineinstrs -target-abi ilp32 -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.*`	0	16	remark: <unknown>:0:0: unable to legalize instruction: %3:_(<8 x s8>) = G_INSERT_VECTOR_ELT %0:_, %4:_(s8), %5:_(s32) (in function: poison) warning: Instruction selection used fallback path for poison
SelectionDAG (control)	`-mtriple=riscv32 -mattr=+zhinxmin -verify-machineinstrs -target-abi ilp32 -global-isel=0`	0	16	-

Reproduce:

llc -mtriple=riscv32 -mattr=+zhinxmin -verify-machineinstrs -target-abi ilp32 -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv32 -mattr=+zhinxmin -verify-machineinstrs -target-abi ilp32 -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %3:_(<8 x s8>) = G_INSERT_VECTOR_ELT %0:_, %4:_(s8), %5:_(s32) (in function: poison)
warning: Instruction selection used fallback path for poison

Occurrences (13):

Input	Function	Config
calls.4cde1ea7a7.ll (mutant of calls.ll)	defined_function	`-relocation-model=pic -mtriple=riscv32 -verify-machineinstrs`
calls.fbef3ca0c6.ll (mutant of calls.ll)	defined_function	`-mtriple=riscv32 -verify-machineinstrs`
float-imm.b9bc176d76.ll (mutant of float-imm.ll)	poison	`-mtriple=riscv32 -mattr=+f -verify-machineinstrs -target-abi=ilp32f`
fold-masked-merge.601e20c496.ll (mutant of fold-masked-merge.ll)	masked_merge2	`-mtriple=riscv32 -mattr=+zbb`
fold-masked-merge.8ce0b8176f.ll (mutant of fold-masked-merge.ll)	masked_merge2	`-mtriple=riscv32`
half-imm.1ed18322c7.ll (mutant of half-imm.ll)	poison	`-mtriple=riscv32 -mattr=+zhinxmin -verify-machineinstrs -target-abi ilp32`
half-imm.684f9b3603.ll (mutant of half-imm.ll)	poison	`-mtriple=riscv32 -mattr=+zfhmin -verify-machineinstrs -target-abi ilp32f`
half-imm.96204b0a82.ll (mutant of half-imm.ll)	poison	`-mtriple=riscv32 -mattr=+zfh -verify-machineinstrs -target-abi ilp32f`
half-imm.9926f442c5.ll (mutant of half-imm.ll)	poison	`-mtriple=riscv32 -mattr=+zhinx -verify-machineinstrs -target-abi ilp32`
sfb-merge-base-offset.1b03bf03f4.ll (mutant of sfb-merge-base-offset.ll)	load_cond_ga_word_zext	`-mtriple=riscv32 -verify-machineinstrs -mattr=+xqci,+short-forward-branch-iload`
sfb-merge-base-offset.fbb431a2f3.ll (mutant of sfb-merge-base-offset.ll)	load_cond_ga_word_zext	`-mtriple=riscv32 -verify-machineinstrs -mattr=+short-forward-branch-iload`
stack-clash-prologue.7223f8eaed.ll (mutant of stack-clash-prologue.ll)	f2	`-mtriple=riscv32 -mattr=+m -O2`
xqcisls-merge-base-offset-shladd.2f48a3ecce.ll (mutant of xqcisls-merge-base-offset-shladd.ll)	load_scaled_i8	`-mtriple=riscv32 -mattr=+xqcili,+xqcisls,+zba,+xqciac -verify-machineinstrs`

Generated 2026-10-15 08:05 UTC.