asm code for SWAP?

I have started translating some floating point intensive forth (SF 2.2.2.9)
into code for speed, and I have been perusing the source for examples of how
to do things. I saw the code for SWAP and had a question:

ICODE SWAP ( x1 x2 -- x2 x1 ) \ exchange top and second

   0 [EBP] EAX MOV

   EBX 0 [EBP] MOV

   EAX EBX MOV

   RET END-CODE

{ EBP is the data stack pointer, and EBX holds the TOS element }

Why not:

ICODE SWAP ( x1 x2 -- x2 x1 ) \ exchange top and second

   0 [EBP] EBX XCHG

   RET END-CODE

?

It seems to work, but maybe there is some obscure reason why not.

Also, I thought I should be able to do a 2 # AL SHL but when I do a

code zzz EBX EAX MOV 2 # AL SHL EAX EBX MOV RET END-CODE it assembles with
no errors, but when I run it I get an ACCESS_VIOLATION.

MHKnowles

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Received on Sat Mar 22 2003 - 18:40:09 PST