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    SubjectRe: [PATCH] x86/asm: Add support for MOVDIR64B instruction
    On Thu, Aug 01, 2019 at 12:49:48PM -0700, Luck, Tony wrote:
    > On Thu, Aug 01, 2019 at 10:43:48PM +0300, Alexey Dobriyan wrote:
    > > > +static inline void movdir64b(void *dst, const void *src)
    > > > +{
    > > > + /* movdir64b [rdx], rax */
    > > > + asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02"
    > > > + : "=m" (*(char *)dst)
    > > ^^^^^^^^^^
    > >
    > > > + : "d" (src), "a" (dst));
    > > > +}
    > >
    > > Probably needs fake 64-byte type, so that compiler knows what is dirty.
    >
    > Would that be something like this?
    >
    > static inline void movdir64b(void *dst, const void *src)
    > {
    > struct dstbytes {
    > char pad[64];
    > };
    >
    > /* movdir64b [rdx], rax */
    > asm volatile(".byte 0x66, 0x0f, 0x38, 0xf8, 0x02"
    > : "=m" (*(struct dstbytes *)dst)
    > : "d" (src), "a" (dst));
    > }
    >
    > Or did you have something else in mind?

    Well, it doesn't need a name:

    : "=m" (*(struct{char _[64];}*)dst)

    But yes, something like that.

    Can't cast to "char[64]" :-(

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