Running 32-bit builds on a Win7 system

[axn]

Originally Posted by ewmayer

Retina, based on your comment - coupled with the fact that Visual studio does seem to be diligent about not inducing ASM-inlining-related clobbers other than the one the user specifies - I expected to see something like this in the assembler output when I generated it over the weekend:

add ecx,edi
movaps xmm0,[ecx]
sub ecx,edi

No. Subtraction is what is not supported by x86. Addition is.

[ewmayer]

Originally Posted by axn

No. Subtraction is what is not supported by x86. Addition is.

Ah - misread your note the first time around ... and a little more diggong resolves the mystery...

Note that I only actually use the + (register-add) form in my functional macros. After getting those working to make sure the [ecx+edi] - style addressing format worked, I wrote a simple one-line test macro to see if the minus form also worked. That compiled without complaint, so I assumed it did.

When I look at the assembler output and search for the minus-form test macro, it does not appear, apparently since it is not used. When I actually inlined it in some code just now, I did in fact get a compile error:

error C2425: '-' : non-constant expression in 'second operand'

So one would in fact need to do an explicit negation to effect such an address computation. Analogously, when I try to inline a non-power-of-2 scale factor like [ecx+5*edi], the compiler gives

error C2423: '5' : illegal scale