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Re: [patch] Handle return small struct in rs600 (size is not 4/8)
On Monday 15 August 2011 17:56:09, Yao Qi wrote:
> I think the description "shall be returned in r3 and r4, as if they were
> first stored in memory area and then the low-addressed word were loaded
> in r3 ...." is not very clear on the length of data. In this case,
> struct C variable is returned, and its content is 0x61 0x62 0x63. They
> (3 bytes) are stored in memory, and (3 bytes) are loaded into r3. Since
> 3 bytes, not 4, are loaded to r3, so I believe r3 should be 0x616263,
> instead of 0x61626300.
I agree with Mark's interpretation (FWIW).
By my reading, for a 3-byte struct c, if the raw memory content of c stored
at AS-IF-ADDRESS in memory is 0x616263XX, then, when you load the
contents of the low-addressed word (4 bytes) starting at AS-IF-ADDRESS
to r3, you get 0x616263XX in r3.
For a 5-byte struct c, if the raw memory content of c at AS-IF-ADDRESS
is 0x6162636465XXXXXX, then, when you load the contents of the
low-addressed word starting at AS-IF-ADDRESS to r3, you
get 0x61626364 in r3; and then loading the contents of high-word at
AS-IF-ADDRESS gets you 0x65XXXXXX in r4.