fallback: legalize: G_ATOMICRMW_ADD s64,p0

Run:explore-04ca53e65f-20261014-114124
Kind:fallback
Category:legalize: G_ATOMICRMW_ADD s64,p0
Occurrences:10 in 3 configs, 3 test files
Snippet from:forced-atomics.ll @rmw64_monotonic 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_monotonic(ptr %p) #0 {
  %v = atomicrmw add ptr %p, i64 1 monotonic, 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_ADD %0:_(p0), %2:_ :: (load store monotonic (s64) on %ir.p) (in function: rmw64_monotonic)
warning: Instruction selection used fallback path for rmw64_monotonic

Occurrences (10):

InputFunctionConfig
atomic-rmw.llatomicrmw_add_i64_monotonic-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs
atomic-rmw.llatomicrmw_add_i64_acquire-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs
atomic-rmw.llatomicrmw_add_i64_release-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs
atomic-rmw.llatomicrmw_add_i64_acq_rel-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs
atomic-rmw.llatomicrmw_add_i64_seq_cst-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs
atomic-signext.llatomicrmw_add_i64_monotonic-mtriple=riscv64 -mattr=+zalrsc -verify-machineinstrs
forced-atomics.llrmw64_monotonic-mtriple=riscv64 -mattr=+forced-atomics
forced-atomics.llrmw64_add_seq_cst-mtriple=riscv64 -mattr=+forced-atomics
forced-atomics.llrmw64_monotonic-mtriple=riscv64 -mattr=+forced-atomics,+no-trailing-seq-cst-fence
forced-atomics.llrmw64_add_seq_cst-mtriple=riscv64 -mattr=+forced-atomics,+no-trailing-seq-cst-fence

Generated 2026-10-15 08:05 UTC.