[Bug c/96365] GCC report impossible constraint on possible inline assembly output constraints

141242068 at smail dot nju.edu.cn gcc-bugzilla@gcc.gnu.org
Wed Jul 29 10:12:07 GMT 2020


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96365

--- Comment #2 from wierton <141242068 at smail dot nju.edu.cn> ---
(In reply to Jakub Jelinek from comment #1)
> Any reason why you can't just write "=a"(x), "=b"(y), "=c"(z) if you mean
> that as the only possibility?

Emm, I was studying the inline assembly by reading the manual on
https://gcc.gnu.org/onlinedocs/gcc/Using-Assembly-Language-with-C.html#Using-Assembly-Language-with-C.
This example was accidently found because I wondered that if GCC really
considers constraints allocation as constraint solving problem. It seems that
GCC takes simpler strategy such as greedy algorithm and this may violate the
specification. I was not very sure if it is really inconsistent with
specification (I failed in finding accurate description), but I thought posting
this example may help improve the quality of GCC (or specification).


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