[Bug inline-asm/11203] source doesn't compile with -O0 but they compile with -O3

["astrange at ithinksw dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #40 from astrange at ithinksw dot com  2009-10-18 19:56 -------
Linked from http://x264dev.multimedia.cx/?p=185, I'd forgotten all about the
ridiculous flamewar in this one.

Just as a note, the actual definitions of the four variables (from liba52):
  x2k = x + 2 * k;
  x3k = x2k + 2 * k;
  x4k = x3k + 2 * k;
  wB = wTB + 2 * k;

Also, the asm inputs are silly - output 0 is the same as input 6 for no reason,
and the same with output 2 and input 7. So change those to "+m" and change
%6/%7 to %0/%2.

That doesn't actually change anything, even though it should free two
registers. It works with gcc 4.5 -O0 -fno-pic -fomit-frame-pointer, but not
without one of those flags. Looks like that's because it's allocating 2 more
registers for the unused fake inputs for the "+m" - change it to "=m" and it
works with one flag removed, but still not both. So there's a specific bug.

And of course it all works at -O1 because it doesn't have to use registers
there. So maybe it should just do that.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203