On Wed, 8 Apr 2020, Vineet Gupta via Libc-alpha wrote:
> +# define _FPU_SETS(cw) __asm__ volatile ("bset %0, %0, 31 \r\n" \
> + "sr %0, [0x301] \r\n" \
> + : : "r" (cw))
This asm doesn't look safe; it's modifying an input operand. I think the
compiler will assume the register it puts %0 in is unmodified by the asm,
because it's listed as an input.
As an architecture-specific interface, it's not very clear if the
interface for _FPU_SETS should be that it modifies the variable passed as
an argument, but I'd guess not. My suggestion would be to define the
macro (using do { ... } while (0)) to copy the argument to a temporary
variable, and do the bit-set operation in C code on that temporary
variable rather than as part of the asm.
--
Joseph S. Myers
[email protected]
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