On Fri, Oct 8, 2021 at 4:21 PM Denys Vlasenko <[email protected]> wrote:
> Can you try this?
>
> #if defined(__clang_major__) && __clang_major__ >= 9
> /* Clang/llvm drops assignment to "constant" storage. Silently.
> * Needs serious convincing to not eliminate the store.
> */
> static ALWAYS_INLINE void register_barrier(void)
> {
> int r0, r1, r2, r3, r4, r5;
> asm volatile (
> "# clobber 6 registers"
> : "=r"(r0), "=r"(r1), "=r"(r2), "=r"(r3), "=r"(r4), "=r"(r5)
> : "0"(r1), "1"(r1), "2"(r2), "3"(r3), "4"(r4), "5"(r5)
> : "memory"
>
> );
> }
should be "0"(r0), not r1; also, dummy-initialize them to avoid warnings:
static ALWAYS_INLINE void register_barrier(void)
{
int r0 = r0, r1 = r1, r2 = r2, r3 = r3, r4 = r4, r5 = r5;
asm volatile (
"# clobber 6 registers"
: "=r"(r0), "=r"(r1), "=r"(r2), "=r"(r3), "=r"(r4), "=r"(r5)
: "0"(r0), "1"(r1), "2"(r2), "3"(r3), "4"(r4), "5"(r5)
: "memory"
);
}
6 registers is maximum what does not fail to compile for i386.
Size growth +1021 bytes.
5 registers: +564 bytes
4 registers: +424 bytes
3 registers: +303 bytes
2 registers: +205 bytes
1 register: +101 bytes
0 registers: 0 bytes (as expected)
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