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[Bug c/59615] "asm goto" output or at least clobbered operands
- From: "glisse at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 30 Dec 2013 17:52:55 +0000
- Subject: [Bug c/59615] "asm goto" output or at least clobbered operands
- Auto-submitted: auto-generated
- References: <bug-59615-4 at http dot gcc dot gnu dot org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59615
--- Comment #6 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #4)
> Anyway, you definitely don't want
> to use inline asm in this case, if there is some code GCC doesn't optimize
> as good as you'd like to, just report that.
One common similar case where people are tempted to use asm goto with an output
operand is, on x86: compute a*b and check if it overflowed. x86 has flags for
that but AFAIR they are not modeled in the .md files. (I was also interested in
output operands for asm goto in PR52381, but there is no good example there)