x87 register clobber returns "unknown register name" error
Mon Jan 4 20:55:00 GMT 2016
Thanks for the tip, and sorry for my late reply. I have been moving and
lost internet connectivity for a while.
If the "st" clobber provides no details regarding which stack registers
will be used, does it mean that the GCC register allocator has no way to
know how many stack registers are needed and must invalidate all x87
registers in order to take the safe route ?
In any case, if this is the proper syntax, the GCC manual should perhaps
be modified, as in the last example of its section 184.108.40.206 "x86
Floating-Point asm Operands" (bottom of
https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html ) it suggests that
st(x) can be used as a clobber.
Le 11/12/2015 09:07, Bernd Edlinger a Ã©crit :
> Hi Hadrien,
>> asm volatile ("fstps (%1)" :
>> : // No output
>> "t" (input), "r" (output) :
>> "memory", "st(0)");
> st(0) may work in assembler, but in the clobber section you must write "st".
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