I feel like inline assembly is a very niche idea. Inline assembly is
supported by c and by extension objective-c.
//file.h
void aCFunction();
//file.m
void aCFunction() {
int a=10, b;
asm ("movl %1, %%eax;
movl %%eax, %0;"
:"=r"(b) /* output */
:"r"(a) /* input */
:"%eax" /* clobbered register */
);
}
I found the assembly code here:
http://www.ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html
But theoretically you should be able to call this assembly code via
aCFunction() in swift.
I understand that it might be fun to do assembly in swift but I feel like
low level code should stay in its territory; if you want to do low level
programming write c code, if you want to go lower than that, leverage
inline assembly within the boundaries of c.
···
On Sat, Dec 3, 2016 at 7:23 PM Chris Lattner via swift-evolution < swift-evolution@swift.org> wrote:
> On Dec 3, 2016, at 3:12 PM, Ethin Probst via swift-evolution < > swift-evolution@swift.org> wrote:
>
> Hello all,
> My name is Ethin and I am new to this community. However, I certainly
> am no newbie when it comes to software development, and have emailed
> all of you to file a proposal of inline assembly in Swift. The
> assembly language would be within an asm {...} block.Hi Ethin,
While it isn’t a pressing short term priority, I would like to see
something to address the needs served by inline assembly in Swift at some
point. We have a lot of experience from the Clang/C space to draw on here,
and there are three general approaches supported by Clang:1) “Processor Intrinsics" for instructions. Compilers for some
architectures provide this as the only option (Itanium in MSVC IIRC).
2) “Microsoft” or “CodeWarrior” style inline assembly, like you show.
This doesn’t require the developer to write register constraints, and
sometimes allows direct use of local variables in the asm block.
3) “GCC” style inline assembly, which requires the user to write register
constraints like “rmi”.I’m significantly opposed to ever supporting GCC-style assembly, since it
is very very common for developers to get the constraints wrong, and the
compiler knows the instruction set anyway.When it comes to #1 vs #2, there are tradeoffs:
#1 is simpler, doesn’t require language extensions (and can be done today
by a sufficiently motivated person), and composes better with
processor-independent intrinsics (like cross platform prefetch operations).#2 is better for folks who “think in assembly”, because it has a more
obvious and direct mapping to it. It has the additional downside of having
to deal with multiple dialects of assembly, e.g. AT&T vs Intel syntax.-Chris
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