Re: [PATCH] x86: bitops: fix build regression

[Peter Zijlstra]

On Tue, May 05, 2020 at 11:07:24AM -0700, hpa@xxxxxxxxx wrote:
> On May 5, 2020 10:44:22 AM PDT, Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote:

> >@@ -54,7 +54,7 @@ arch_set_bit(long nr, volatile unsigned long *addr)
> > 	if (__builtin_constant_p(nr)) {
> > 		asm volatile(LOCK_PREFIX "orb %1,%0"
> > 			: CONST_MASK_ADDR(nr, addr)
> >-			: "iq" (CONST_MASK(nr) & 0xff)
> >+			: "iq" ((u8)(CONST_MASK(nr) & 0xff))
> > 			: "memory");
> > 	} else {
> > 		asm volatile(LOCK_PREFIX __ASM_SIZE(bts) " %1,%0"
> >@@ -74,7 +74,7 @@ arch_clear_bit(long nr, volatile unsigned long *addr)
> > 	if (__builtin_constant_p(nr)) {
> > 		asm volatile(LOCK_PREFIX "andb %1,%0"
> > 			: CONST_MASK_ADDR(nr, addr)
> >-			: "iq" (CONST_MASK(nr) ^ 0xff));
> >+			: "iq" ((u8)(CONST_MASK(nr) ^ 0xff)));
> > 	} else {
> > 		asm volatile(LOCK_PREFIX __ASM_SIZE(btr) " %1,%0"
> > 			: : RLONG_ADDR(addr), "Ir" (nr) : "memory");
> 
> Drop & 0xff and change ^ 0xff to ~.

But then we're back to sparse being unhappy, no? The thing with ~ is
that it will set high bits which will be truncated, which makes sparse
sad.