[pypy-dev] Spurious dict lookups in my JIT loops

[Benjamin Peterson]

This would probably be easier if you showed us the code.

2011/9/17 Boris <boris2010 at boristhebrave.com>:
> Hi,
>
> I've been trying out writing my own interpreter using the PyPy framework
> recently, as a bit of fun. I've been trying to get the JIT to optimize a
> trivial loop down to the minimal amount of operations. With judicious use of
> `_immutable_fields_` and `_virtualizable2_`, I've got pretty close.
>
> But I'm still seeing lots of calls to
> `ll_dict_lookup__dicttablePtr_Signed_Signed`, which don't correspond to any
> code in my interpreter. I don't think I even have any dicts that take
> integer keys. Could someone give me a hint where these are coming from and
> for what purpose? Or perhaps how to inspect the dicts or get further info?
>
> I append what I'm seeing in the logs (Note: I've augmented the logs to give
> the raw pointer). In this case, it is only looking up the value 21, but I've
> seen other values in addition when running other programs. The
> setarrayitem_gc calls are expected - it is nulling out the stack that was
> being used. Everything from i17 is unexpected. I tested on revisions
> 00711ff1e03d and 96a212b0688a.
>
> Thanks,
>
> Boris
>
>
> #############################
>
> [3fd12ea6569db] {jit-log-opt-loop
> # Loop 0 : loop with 37 ops
> [p0, p1, p2, i3, p4, p5]
> debug_merge_point(0, '::Test$iinit:20')
> +113: i7 = int_add(i3, 1)
> debug_merge_point(0, '::Test$iinit:22')
> debug_merge_point(0, '::Test$iinit:23')
> debug_merge_point(0, '::Test$iinit:26')
> +116: setarrayitem_gc(p5, 0, ConstPtr(ptr9,0x0), descr=<GcPtrArrayDescr>)
> +126: setarrayitem_gc(p5, 1, ConstPtr(ptr11,0x0), descr=<GcPtrArrayDescr>)
> +133: i13 = uint_lt(i7, 10000)
> guard_true(i13, descr=<Guard2>) [p0, p1, p2, p4, i7]
> +145: i17 = call(ConstClass(ll_dict_lookup__dicttablePtr_Signed_Signed),
> ConstPtr(ptr15,0x84c2958), 21, 21, descr=<SignedCallDescr>)
> +176: guard_no_exception(, descr=<Guard3>) [p0, i17, p1, p2, p4, i7]
> +189: i19 = int_and(i17, -2147483648)
> +195: i20 = int_is_true(i19)
> guard_true(i20, descr=<Guard4>) [p0, p1, p2, p4, i7]
> +204: i23 = call(ConstClass(ll_dict_lookup__dicttablePtr_Signed_Signed),
> ConstPtr(ptr22,0x84c2978), 21, 21, descr=<SignedCallDescr>)
> +235: guard_no_exception(, descr=<Guard5>) [p0, i23, p1, p2, p4, i7]
> +248: i24 = int_and(i23, -2147483648)
> +254: i25 = int_is_true(i24)
> guard_true(i25, descr=<Guard6>) [p0, p1, p2, p4, i7]
> +263: i28 = call(ConstClass(ll_dict_lookup__dicttablePtr_Signed_Signed),
> ConstPtr(ptr27,0x84c2988), 21, 21, descr=<SignedCallDescr>)
> +294: guard_no_exception(, descr=<Guard7>) [p0, i28, p1, p2, p4, i7]
> +307: i29 = int_and(i28, -2147483648)
> +313: i30 = int_is_true(i29)
> guard_true(i30, descr=<Guard8>) [p0, p1, p2, p4, i7]
> +322: i33 = call(ConstClass(ll_dict_lookup__dicttablePtr_Signed_Signed),
> ConstPtr(ptr32,0x84c2998), 21, 21, descr=<SignedCallDescr>)
> +353: guard_no_exception(, descr=<Guard9>) [p0, i33, p1, p2, p4, i7]
> +366: i34 = int_and(i33, -2147483648)
> +372: i35 = int_is_true(i34)
> guard_false(i35, descr=<Guard10>) [p0, p1, p2, p4, i7]
> +381: i38 = call(ConstClass(ll_dict_lookup__dicttablePtr_Signed_Signed),
> ConstPtr(ptr37,0x84c2968), 21, 21, descr=<SignedCallDescr>)
> +412: guard_no_exception(, descr=<Guard11>) [p0, i38, p1, p2, p4, i7]
> +425: i39 = int_and(i38, -2147483648)
> +431: i40 = int_is_true(i39)
> guard_true(i40, descr=<Guard12>) [p0, p1, p2, p4, i7]
> debug_merge_point(0, '::Test$iinit:20')
> +440: i41 = arraylen_gc(p5, descr=<GcPtrArrayDescr>)
> +440: jump(p0, p1, p2, i7, p4, p5, descr=<Loop0>)
> +448: --end of the loop--
> [3fd12ea696ce9] jit-log-opt-loop}
>
>
>
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>



-- 
Regards,
Benjamin