fallback: legalize: G_UDIV <2 x s64>

Run:	explore-04ca53e65f-20261014-114124
Kind:	fallback
Category:	legalize: G_UDIV <2 x s64> NEW
Occurrences:	3 in 3 configs, 2 test files
Snippet from:	rv64zbb.3e426b4f52.ll (mutant of rv64zbb.ll) @sexth_extract_i32 via llvm-extract + llvm-reduce
Config:	`-mtriple=riscv64 -mattr=+zbb -verify-machineinstrs`
Local check:	reproduces at 04ca53e65f
Compiler Explorer:	https://godbolt.org/z/e5rqGrjP5 (llc-assertions-trunk, checked 2026-10-14 11:50 UTC): G reproduces

Snippet:

define <2 x i64> @sexth_extract_i32() {
  %B = udiv <2 x i64> splat (i64 1), zeroinitializer
  ret <2 x i64> %B
}

Compiler Explorer panes:

Pane	Options	Exit	Insts	stderr
GlobalISel	`-mtriple=riscv64 -mattr=+zbb -verify-machineinstrs -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.*`	0	1	remark: <unknown>:0:0: unable to legalize instruction: %4:_(<2 x s64>) = G_UDIV %0:_, %2:_ (in function: sexth_extract_i32) warning: Instruction selection used fallback path for sexth_extract_i32
SelectionDAG (control)	`-mtriple=riscv64 -mattr=+zbb -verify-machineinstrs -global-isel=0`	0	1	-

Reproduce:

llc -mtriple=riscv64 -mattr=+zbb -verify-machineinstrs -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv64 -mattr=+zbb -verify-machineinstrs -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %4:_(<2 x s64>) = G_UDIV %0:_, %2:_ (in function: sexth_extract_i32)
warning: Instruction selection used fallback path for sexth_extract_i32

Occurrences (3):

Input	Function	Config
pei-crash.d8853e1c84.ll (mutant of pei-crash.ll)	a	`-O0 --frame-pointer=none -mtriple=riscv32 -mattr=+zcmp -verify-machineinstrs`
rv64zbb.3e426b4f52.ll (mutant of rv64zbb.ll)	sexth_extract_i32	`-mtriple=riscv64 -mattr=+zbb -verify-machineinstrs`
rv64zbb.b09d812e9b.ll (mutant of rv64zbb.ll)	sexth_extract_i32	`-mtriple=riscv64 -verify-machineinstrs`

Generated 2026-10-15 08:05 UTC.