On 19/08/16 22:49, Michael Ring wrote:
Am 19.08.16 um 14:49 schrieb Jonas Maebe:
Michael Ring wrote on Sat, 13 Aug 2016:
I am trying to bring interrupt handling routine size down (and speed
up) for mipsel-embedded target.
I need to use inline assembler routines like this one
procedure TSystemCore.setCoreTimerComp(value : longWord); assembler;
nostackframe;
asm
mtc0 $a1,$11,0
end ['a1'];
Mentioning changed registers at the end of a pure assembler routine
has no effect. The compiler normally prints a warning about this. The
set of changed registers by a routine always only depends on its
calling convention. On most platforms we only support the official
ABI's calling convention, which is also the default.
I also tried also something like this:
procedure TSystemCore.setCoreTimerComp(value : longWord);
begin
asm
mtc0 $a1,$11,0
end ['a1'];
end;
with same result, all registers are saved. intead of only a few.
It is not clear what you mean by this. In your original message, you
said that all registers were saved "as soon as I include the call to
this procedure". As explained, the registers that are saved when calling
a routine only depend on what the ABI says are volatile/callee-saved
registers. Which registers are actually used by the called routine have
no influence at all.
Same is true if I put the asm block directly inside of the interrupt
handler.
In that case, the list of changed registers should be taken into
account. OTOH, using an inline assembler blocks disables the use the
use of register variables for that routine by the compiler, but that
should result in less registers getting saved rather than more.
Do you remember where this is coded or for what I should search in the
fpc sourcecode? Then I can try to find out what is going on in the mips
case.
It's the last part of the _asm_statement function in compiler/pstatemnt.pas
FWIW, tcpuparamanager.get_volatile_registers_int() in mips/cpupara.pas
suggests that all integer registers except for R16-R23 are volatile, so
no matter what you do, if any of those registers contains a value that
is still needed after a call, they will be saved and restored.
Jonas
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