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

["steven at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From steven at gcc dot gnu dot org  2005-01-22 12:14 -------
Martin, you should realize that this problem *cannot* be solved.  Yes, 
there will perhaps be a time when this particular test case compiles, 
though I think that is unlikely.  But anyway, then there will be other 
cases that fail. 
 
The reason is dead simple: register allocation is NP-complete, so it 
is even *theoretically* not possible to write register allocators that 
always find a coloring.  That means any register allocator will always 
fail on some very constrained asm input.  And you cannot allow it to 
run indefinitely until a coloring is found, because then you've turned 
the graph coloring problem into the halting problem because you can't 
prove that a coloring exists and that the register allocator algorithm 
will terminate. 
 
So really it doesn't matter at all whether or not your specific inline 
asm compiles or not.  When yours does, someone else's will fail. 
 
 

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