fallback: legalize: G

fallback: legalize: G_SUB <2 x s64>

Run:	explore-bc8218b282-20261015-075519
Kind:	fallback
Category:	legalize: G_SUB <2 x s64> NEW
Occurrences:	15 in 13 configs, 4 test files
Snippet from:	imm.097b546b43.ll (mutant of imm.ll) @imm_right_shifted_addi via llvm-extract + llvm-reduce
Config:	`-mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -verify-machineinstrs -riscv-use-rematerializable-movimm`
Local check:	reproduces at bc8218b282
Compiler Explorer:	https://godbolt.org/z/f9r8casjv (llc-assertions-trunk, checked 2026-10-15 08:05 UTC): G reproduces

Snippet:

define <2 x i64> @imm_right_shifted_addi(<2 x i64> %LGV) {
  %B = srem <2 x i64> %LGV, splat (i64 4294967296)
  ret <2 x i64> %B
}

Compiler Explorer panes:

Pane	Options	Exit	Insts	stderr
GlobalISel	`-mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -verify-machineinstrs -riscv-use-rematerializable-movimm -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.*`	0	13	remark: <unknown>:0:0: unable to legalize instruction: %5:_(<2 x s64>) = G_SUB %17:_, %15:_ (in function: imm_right_shifted_addi) warning: Instruction selection used fallback path for imm_right_shifted_addi
SelectionDAG (control)	`-mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -verify-machineinstrs -riscv-use-rematerializable-movimm -global-isel=0`	0	13	-

Reproduce:

llc -mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -verify-machineinstrs -riscv-use-rematerializable-movimm -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -verify-machineinstrs -riscv-use-rematerializable-movimm -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %5:_(<2 x s64>) = G_SUB %17:_, %15:_ (in function: imm_right_shifted_addi)
warning: Instruction selection used fallback path for imm_right_shifted_addi

Occurrences (15):

Input	Function	Config
alu64.317514652b.ll (mutant of alu64.ll)	srai	`-mtriple=riscv64 -verify-machineinstrs`
alu64.52f3004a1b.ll (mutant of alu64.ll)	srai	`-mtriple=riscv32 -verify-machineinstrs`
double-zfa.d3bfc134ee.ll (mutant of double-zfa.ll)	loadfpimm9	`-mtriple=riscv64 -target-abi lp64d -mattr=+zfa,+d`
double-zfa.e3649335d9.ll (mutant of double-zfa.ll)	loadfpimm9	`-mtriple=riscv32 -target-abi ilp32d -mattr=+zfa,+d`
i64-icmp.f31c0f41db.ll (mutant of i64-icmp.ll)	icmp_ne_constant	`-mtriple=riscv64 -verify-machineinstrs`
imm.097b546b43.ll (mutant of imm.ll)	imm_right_shifted_addi	`-mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -verify-machineinstrs -riscv-use-rematerializable-movimm`
imm.176d557918.ll (mutant of imm.ll)	imm_right_shifted_addi	`-mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -mattr=+zba -verify-machineinstrs`
imm.1a23177c35.ll (mutant of imm.ll)	imm_right_shifted_addi	`-mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -mattr=+xtheadbb -verify-machineinstrs`
imm.25b6fd729d.ll (mutant of imm.ll)	imm_right_shifted_addi	`-mtriple=riscv32 -riscv-constant-pool-for-large-ints=0 -mattr=+xqcili -verify-machineinstrs`
imm.264ced609a.ll (mutant of imm.ll)	imm_right_shifted_addi	`-mtriple=riscv32 -riscv-constant-pool-for-large-ints=0 -verify-machineinstrs -riscv-use-rematerializable-movimm`
imm.284d5739fe.ll (mutant of imm.ll)	imm_right_shifted_addi	`-mtriple=riscv32 -riscv-constant-pool-for-large-ints=0 -verify-machineinstrs`
imm.4213604a23.ll (mutant of imm.ll)	imm_right_shifted_addi	`-mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -mattr=+zbs -verify-machineinstrs`
imm.6df8e2ed25.ll (mutant of imm.ll)	imm_right_shifted_addi	`-mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -verify-machineinstrs`
imm.90ef724a79.ll (mutant of imm.ll)	imm_right_shifted_addi	`-mtriple=riscv64 -verify-machineinstrs`
imm.bbffb4d578.ll (mutant of imm.ll)	imm_right_shifted_addi	`-mtriple=riscv64 -riscv-constant-pool-for-large-ints=0 -mattr=+zbb -verify-machineinstrs`

Generated 2026-10-15 08:05 UTC.