[AArch64] llc crash: Cannot select: t4: i32,ch = AtomicLoadUIncWrap<(load store monotonic (s32) on %ir.p)> t0, t2, Constant:i32<0>

[alexey-bataev]

target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32"
target triple = "aarch64-unknown-linux-gnu"

define i32 @test(ptr %p) #0 {
.lr.ph:
  %0 = atomicrmw uinc_wrap ptr %p, i32 0 monotonic, align 4
  ret i32 %0
}

attributes #0 = { "target-features"="+outline-atomics" }

llc ./reduced.ll results in:

LLVM ERROR: Cannot select: t4: i32,ch = AtomicLoadUIncWrap<(load store monotonic (s32) on %ir.p)> t0, t2, Constant:i32<0>
  t2: i64,ch = CopyFromReg t0, Register:i64 %0
In function: test

[llvmbot]

@llvm/issue-subscribers-backend-aarch64

Author: Alexey Bataev (alexey-bataev)

``` target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32" target triple = "aarch64-unknown-linux-gnu"

define i32 @test(ptr %p) #0 {
.lr.ph:
%0 = atomicrmw uinc_wrap ptr %p, i32 0 monotonic, align 4
ret i32 %0
}

attributes #0 = { "target-features"="+outline-atomics" }

`llc ./reduced.ll` results in:

LLVM ERROR: Cannot select: t4: i32,ch = AtomicLoadUIncWrap<(load store monotonic (s32) on %ir.p)> t0, t2, Constant:i32<0>
t2: i64,ch = CopyFromReg t0, Register:i64 %0
In function: test

</details>

[davemgreen]

There are a number of other missing cases too, that have been added more recently. The list of outline atomic supported operations in AArch64TargetLowering::shouldExpandAtomicRMWInIR should be opt-in, not opt-out.