Inline assembler constraints

[MaxFlashrom]

Hi, I'm having trouble with inline assembly contraints. Specifically, nothing other than "r"(xxx) and "=r"(xxx) seem to work.
I am using the 11.2.1 tools. I want to do in-out paramters, and immediate values would be nice too.

Runes in other gcc manuals suggest that the likes of this works for tmp as an in-out variable, a common pattern on processors which don't have 3-reg RISC capability on most instructions, as XMOS does.

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asm("andnot %0, %2" : "=r"(tmp) : "0"(tmp), "r"(mask));

gives a syntax error.
With

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asm("andnot %0, %2" : "=r"(tmp) : "r"(tmp), "r"(mask));

the compiler just produces nonsense.

Some variants support the use of "+" for in-out, I read i.e.

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asm("andnot %0, %1" : "+r"(tmp) : "r"(mask));

gives a syntax error.

This also does not work

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asm("ldc r0, %0" :: "i"(0xf7));

It avoids the need for the likes of:

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#include <xs1.h>

#define stringify(x) stringify0(x)
#define stringify0(x) #x

asm("getr %0, " stringify(XS1_RES_TYPE_LOCK) : "=r"(lock));

Has anyone made in-out parameters work? The XMOS manual doesn't elaborate beyond simple "r" and "=r" examples.

Regards
Max.

[richard]

The XC compiler currently only supports the constraints listed in the tools user guide. Tied operands and immediate operands are not supported. If you need to use an instruction with a read / write operand then you will need to introduce a move. For example:

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asm("mov %0, %1; andnot %0, %2" : "=&r"(result) : "r"(x), "r"(mask));

Supporting tied operands would avoid the need for the move so its something we would like to support in future.

Edit: fix order of operands

[segher]

I think you swapped the "mov" operands there? It's "mov dst,src" isn 't it?

[richard]

I think you swapped the "mov" operands there? It's "mov dst,src" isn 't it?

Good spot, I've edited my post.