[fpc-devel] Bug with R+ and assembler functionsHi,
jonas.maebe at elis.ugent.be
Thu Nov 3 12:04:31 CET 2005
On 3 nov 2005, at 11:53, Markus Kämmerer wrote:
> .stabn 68,0,257,.Ll49 - EDITOR_FINDUMBRUCH$formal$LONGINT$$LONGINT
> #  mov esi,data
> movl %eax,%esi
> .stabn 68,0,258,.Ll50 - EDITOR_FINDUMBRUCH$formal$LONGINT$$LONGINT
> #  mov ebx,zlen
> movl %edx,%ebx
> .stabn 68,0,259,.Ll51 - EDITOR_FINDUMBRUCH$formal$LONGINT$$LONGINT
> Findumbruch awaits the "data" in esi.
No, in eax. "movl %eax, %esi" means "move the contents of eax into
esi". This is AT&T assembler notation, not Intel.
> With the R+ version, the value is
> loaded to esi before range check.
No, what is loaded in esi is "offset". The range check is to make
sure that in the expression "cont[offset]", offset is not going past
the end of the array.
> In the R- version the value is located
> in ecx and not been copied to esi, which is the bug.
No. At least one problem is that in your assembler function, you use
esi and ebx without saving/restoring them. ebx, esi and edi are
callee-saved registers in the new default calling convention of FPC
2.0 (register calling), just like in C/C++.
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