fallback: legalize: G_ATOMICRMW

fallback: legalize: G_ATOMICRMW_SUB s64,p0

Run:	explore-04ca53e65f-20261014-114124
Kind:	fallback
Category:	legalize: G_ATOMICRMW_SUB s64,p0
Occurrences:	14 in 3 configs, 4 test files
Snippet from:	forced-atomics.ll @rmw64_sub_seq_cst via llvm-extract
Config:	`-mtriple=riscv64 -mattr=+forced-atomics`
Local check:	reproduces at 04ca53e65f
Compiler Explorer:	not uploaded (over --godbolt-limit or disabled)

Snippet:

; Function Attrs: nounwind
define i64 @rmw64_sub_seq_cst(ptr %p) #0 {
  %v = atomicrmw sub ptr %p, i64 1 seq_cst, align 8
  ret i64 %v
}

attributes #0 = { nounwind }

Reproduce:

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

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %1:_(s64) = G_ATOMICRMW_SUB %0:_(p0), %2:_ :: (load store seq_cst (s64) on %ir.p) (in function: rmw64_sub_seq_cst)
warning: Instruction selection used fallback path for rmw64_sub_seq_cst

Occurrences (14):

Input	Function	Config
atomic-rmw-sub.ll	atomicrmw_sub_i64_constant	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-rmw-sub.ll	atomicrmw_sub_i64_neg	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-rmw.ll	atomicrmw_sub_i64_monotonic	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-rmw.ll	atomicrmw_sub_i64_acquire	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-rmw.ll	atomicrmw_sub_i64_release	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-rmw.ll	atomicrmw_sub_i64_acq_rel	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-rmw.ll	atomicrmw_sub_i64_seq_cst	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-signext.ll	atomicrmw_sub_i64_monotonic	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
forced-atomics.ll	rmw64_sub_seq_cst	`-mtriple=riscv64 -mattr=+forced-atomics`
forced-atomics.ll	rmw64_sub_seq_cst	`-mtriple=riscv64 -mattr=+forced-atomics,+no-trailing-seq-cst-fence`
atomic-rmw-sub.2ab1b432d0.ll (mutant of atomic-rmw-sub.ll)	atomicrmw_sub_i64_neg	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-rmw-sub.5131c57b4d.ll (mutant of atomic-rmw-sub.ll)	atomicrmw_sub_i64_constant	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-rmw-sub.b96a155b00.ll (mutant of atomic-rmw-sub.ll)	atomicrmw_sub_i64_neg	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`
atomic-signext.6159e452e8.ll (mutant of atomic-signext.ll)	atomicrmw_sub_i64_monotonic	`-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs`

Generated 2026-10-15 08:05 UTC.