effects: fix effects of atomic pointer operations

As discussed with Jameson earlier, the effects of atomic pointer
operations are not precisely defined.
This commit includes the minimal changes necessary to fix
#57780, but a more extensive audit is planned for later.

- closes #57780

Author: aviatesk

Compiler/src/tfuncs.jl

@@ -2891,7 +2891,12 @@ end
 # whether `f` is pure for inference
 function is_pure_intrinsic_infer(f::IntrinsicFunction)
     return !(f === Intrinsics.pointerref || # this one is volatile
+             f === Intrinsics.atomic_pointerref || # this one is volatile
              f === Intrinsics.pointerset || # this one is never effect-free
+             f === Intrinsics.atomic_pointerset || # this one is never effect-free
+             f === Intrinsics.atomic_pointerswap || # this one is never effect-free
+             f === Intrinsics.atomic_pointermodify || # this one is never effect-free
+             f === Intrinsics.atomic_pointerreplace || # this one is never effect-free
              f === Intrinsics.llvmcall ||   # this one is never effect-free
              f === Intrinsics.sqrt_llvm_fast ||  # this one may differ at runtime (by a few ulps)
              f === Intrinsics.have_fma ||  # this one depends on the runtime environment

stdlib/REPL/test/replcompletions.jl

@@ -2484,3 +2484,9 @@ let (c, r, res) = test_complete_context("global xxx::Number = Base.", Main)
     @test res
     @test "pi" ∈ c
 end
+
+# JuliaLang/julia#57780
+const issue57780 = ["a", "b", "c"]
+const issue57780_orig = copy(issue57780)
+test_complete_context("empty!(issue57780).", Main)
+@test issue57780 == issue57780_orig