[m-rev.] for review: pack small args next to local secondary tags

[Julien Fischer]

On Tue, 3 Jul 2018, Julien Fischer wrote:

> On Mon, 2 Jul 2018, Zoltan Somogyi wrote:
>
>>  For review by anyone. Note that so far, I have bootchecked it
>>  only in asm_fast.gc and hlc.gc with the new data representation
>>  enabled, but I will test it in other grades and with the new
>>  representation
>>  disabled before commit.
>
> There are few tests cases (on my system) related to fixed size integers
> currently failing in decldebug grades.  (One of which is the argument
> packing test.)  (I've been meaning to investigate, but other things
> keep getting in the way.)

Specifically, in asm_fast.gc.decldebug.trseg.stseg, the following 
fail on my system (x86-64,linux):

    hard_coded/arith_int16
    hard_coded/arith_int32
    hard_coded/arith_int8
    hard_coded/pack_int32

The packing one is most likely failing bcause the arithmetic ones are.
(This looks like a regression of the issue fixed in commit b765dae,
but it isn't since the test case for that passes.)

Julien.