Hi,
On Fri, 23 Sep 2011 10:52:17 +0200, Jonas Maebe wrote:
On 23 Sep 2011, at 01:21, Thomas Schatzl wrote:
I found that 18251 is okay, but the newer ones are not when
compiling with -O2. It seems that one optimization that transforms
expressions of type x*x into sqr(x) for floats in 18252 (and 18257
and 18263 that seem to have been fixing issues with the original
implementation) causes troubles. With that in place, a compiler cycle
hangs at ppc2 compiling something (processing real2str.inc from the
system unit fyi).
Florian, Jonas, any ideas? Seems to be related to softfloat code
generation because apparently other platforms are fine.
The optimization changes x*x into sqr(x). For ARM/softfloat, the
compiler calls the fpc_sqr_real() helper from the RTL.
The code of this helper is:
function fpc_sqr_real(d : ValReal) : ValReal;compilerproc;{$ifdef
MATHINLINE}inline;{$endif}
begin
result := d*d;
end;
So yes, this clearly puts the compiler into an endless loop. I'm not
sure what would be a clean fix for this (other than completely
Other options I see:
- disable if using softfloat knowing that the soft float code just
transforms this into the same code sequence again
- move it to i386 specific optimizations since afaik it is the only
arch which has an instruction which benefits from that.
disabling the transformation; does it improve the generated code that
much beyond what CSE can achieve?)
I doubt it has any noticeable impact.
Thomas
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