jax-metal: inconsistent index clipping in jax.lax.dynamic_slice

[jonatanklosko]

Description

import jax
import jax.numpy as jnp

def f(x, idx):
  return jax.lax.dynamic_slice(x, [idx], [2])

x = jnp.array([1, 2, 3])
idx = jnp.array(2)

# Print lowered HLO
print(jax.jit(f).lower(x, idx).as_text())
print(jax.jit(f)(x, idx))

In the example above idx is too high and there are not enough elements to slice (start_index + length <= dimension). In such case, the index should be clipped to 1, returning [2, 3] in this case (this is the current behaviour on the CPU platform). jax-metal returns [3, 3], but it actually behaves correctly if we replace idx with the constant 2 (the operation doesn't change).

System info (python version, jaxlib version, accelerator, etc.)

jax:    0.4.26
jaxlib: 0.4.26
numpy:  1.26.4
python: 3.10.8 (main, Nov 16 2022, 12:45:33) [Clang 14.0.0 (clang-1400.0.29.202)]
jax.devices (1 total, 1 local): [METAL(id=0)]
process_count: 1
platform: uname_result(system='Darwin', node='chonker', release='23.5.0', version='Darwin Kernel Version 23.5.0: Wed May  1 20:12:58 PDT 2024; root:xnu-10063.121.3~5/RELEASE_ARM64_T6000', machine='arm64')

jax-metal 0.0.7