Bug ? [vsqrtss xmmreg,xmmreg,mem128] invalid combination of opcode and
operand
lazarus / 64-FPC development

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Nitorami · 2018-07-11 16:47

I get an error message on compiling this bit of code. Windows10 & 7,
FPC 3.0.4.  Can anybody test and confirm this please ? Seems to be a
problem with AVX instruction set and optimisation for register
variables. CPU-Z reports that my machine supports the AVX instruction
set, so I suspect this is a bug.

Compile with: fpc mist.pas -CfSSE2 -CpCOREAVX -Mobjfpc -O2 -Twin32

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i //fpc
mist.pas -CfSSE2 -CpCOREAVX -Mobjfpc -O2 -Twin32 type float = single; 
   TVector = array of float;     TMatrix = array of TVector;  function
mtx_cholesky (const a:TMatrix):TMatrix;var l : TMatrix;    c :
float;begin  c := 3;  c := sqrt(c); //-> invalid combination of opcode
and operand  SetLength (l,3,3);  l[0,0]:=c;  result:=l;end; beginend.

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ASerge · 2018-07-11 17:54

Confirm.
It is interesting that if you add the generation of asm code (-al),
then everything passes.
Code: ASM  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i ...# [12] c
:= 3;        vmovss  _$PROGRAM$_Ld1,%xmm0        movss  
%xmm0,-56(%ebp)# [13] c := sqrt(c); //-> invalid combination of opcode
and operand        vsqrtss -56(%ebp),%xmm0,%xmm0        vmovss 
%xmm0,-56(%ebp)...

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Nitorami · 2018-07-11 19:16

Indeed, very odd. I will file a bug report.

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marcov · 2018-07-11 20:38

Did you try -CfAVX ?

Seems a bit strange to allow AVX instructions, but not for the CPU?

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Nitorami · 2018-07-11 21:07

Yes, same behaviour.