fallback: legalize: G

fallback: legalize: G_SUB <2 x s64>

Run:	main-04ca53e65f-20261014-113325
Kind:	fallback
Category:	legalize: G_SUB <2 x s64> NEW
Occurrences:	31 in 27 configs, 6 test files
Snippet from:	div.40842d0458.ll (mutant of div.ll) @udiv16_constant via llvm-extract + llvm-reduce
Config:	`-mtriple=riscv64 -verify-machineinstrs`
Local check:	reproduces at 04ca53e65f
Compiler Explorer:	https://godbolt.org/z/snfTe94Ee (llc-assertions-trunk, checked 2026-10-14 11:04 UTC): G reproduces

Snippet:

define <2 x i64> @udiv16_constant(<2 x i64> %LGV) {
  %B = urem <2 x i64> %LGV, splat (i64 42)
  ret <2 x i64> %B
}

Compiler Explorer panes:

Pane	Options	Exit	Insts	stderr
GlobalISel	`-mtriple=riscv64 -verify-machineinstrs -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.*`	0	18	remark: <unknown>:0:0: unable to legalize instruction: %23:_(<2 x s64>) = G_SUB %0:_, %22:_ (in function: udiv16_constant) warning: Instruction selection used fallback path for udiv16_constant
SelectionDAG (control)	`-mtriple=riscv64 -verify-machineinstrs -global-isel=0`	0	18	-

Reproduce:

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

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %23:_(<2 x s64>) = G_SUB %0:_, %22:_ (in function: udiv16_constant)
warning: Instruction selection used fallback path for udiv16_constant

Occurrences (31):

Input	Function	Config
atomic-load-store.10db122773.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv32 -mattr=+a,+zalasr,+ztso -verify-machineinstrs`
atomic-load-store.1fcf9b6b71.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv32 -mattr=+a,+ztso,+no-trailing-seq-cst-fence -verify-machineinstrs`
atomic-load-store.2f9f7af717.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv64 -mattr=+a,+zalasr,+ztso -verify-machineinstrs`
atomic-load-store.3b0536ca92.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv64 -mattr=+a -verify-machineinstrs`
atomic-load-store.47ac975303.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv32 -verify-machineinstrs`
atomic-load-store.47aee157c6.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv32 -mattr=+a,+zalasr -verify-machineinstrs`
atomic-load-store.58b30de2d8.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-load-store.8733416b80.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv32 -mattr=+zalrsc -verify-machineinstrs`
atomic-load-store.8b32e0d0ec.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv32 -mattr=+a,+no-trailing-seq-cst-fence -verify-machineinstrs`
atomic-load-store.9b79b07db1.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv32 -mattr=+a -verify-machineinstrs`
atomic-load-store.a59725629a.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv64 -mattr=+a,+zalasr -verify-machineinstrs`
atomic-load-store.b69299a220.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv64 -mattr=+a,+ztso,+no-trailing-seq-cst-fence -verify-machineinstrs`
atomic-load-store.bd0aef21fa.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv64 -verify-machineinstrs`
atomic-load-store.c443bc3048.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv32 -mattr=+a,+ztso -verify-machineinstrs`
atomic-load-store.ed15860eaf.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv64 -mattr=+a,+no-trailing-seq-cst-fence -verify-machineinstrs`
atomic-load-store.fdedea1651.ll (mutant of atomic-load-store.ll)	atomic_load_i64_unordered	`-mtriple=riscv64 -mattr=+a,+ztso -verify-machineinstrs`
div.40842d0458.ll (mutant of div.ll)	udiv16_constant	`-mtriple=riscv64 -verify-machineinstrs`
div.bfbed72c98.ll (mutant of div.ll)	udiv16_constant	`-mtriple=riscv32 -mattr=+m -verify-machineinstrs`
div.f5c85855dc.ll (mutant of div.ll)	udiv16_constant	`-mtriple=riscv64 -mattr=+m -verify-machineinstrs`
div.f689fbfb46.ll (mutant of div.ll)	udiv16_constant	`-mtriple=riscv32 -verify-machineinstrs`
double-zfa.97fd116c66.ll (mutant of double-zfa.ll)	loadfpimm13	`-mtriple=riscv32 -target-abi ilp32d -mattr=+zfa,+d`
double-zfa.c621cb871e.ll (mutant of double-zfa.ll)	loadfpimm13	`-mtriple=riscv64 -target-abi lp64d -mattr=+zfa,+d`
float-zfa.83aaaea0ac.ll (mutant of float-zfa.ll)	loadfpimm13	`-mtriple=riscv64 -target-abi lp64f -mattr=+zfa`
float-zfa.9aa4a54701.ll (mutant of float-zfa.ll)	loadfpimm13	`-mtriple=riscv32 -target-abi ilp32f -mattr=+zfa`
inline-asm-mem-constraint.71ac089dfb.ll (mutant of inline-asm-mem-constraint.ll)	constraint_m_with_extern_weak_global_3	`-mtriple=riscv64 -code-model=large -verify-machineinstrs`
inline-asm-mem-constraint.ffd6aa0277.ll (mutant of inline-asm-mem-constraint.ll)	constraint_m_with_extern_weak_global_3	`-mtriple=riscv64 -code-model=large -verify-machineinstrs -no-integrated-as`
prefetch.09de1d0e02.ll (mutant of prefetch.ll)	test_prefetch_instruction_locality_2	`-mtriple=riscv32 -verify-machineinstrs`
prefetch.a629dfea38.ll (mutant of prefetch.ll)	test_prefetch_instruction_locality_2	`-mtriple=riscv64 -mattr=+zicbop,+zihintntl -verify-machineinstrs`
prefetch.c98fb915b1.ll (mutant of prefetch.ll)	test_prefetch_instruction_locality_2	`-mtriple=riscv32 -mattr=+zicbop -verify-machineinstrs`
prefetch.edfad876ef.ll (mutant of prefetch.ll)	test_prefetch_instruction_locality_2	`-mtriple=riscv64 -verify-machineinstrs`
prefetch.fdedbfb304.ll (mutant of prefetch.ll)	test_prefetch_instruction_locality_2	`-mtriple=riscv64 -mattr=+zicbop -verify-machineinstrs`

Generated 2026-10-15 08:05 UTC.