On 07/16/2017 10:03 AM, Emilio G. Cota wrote:
+ if (likely(tb &&
+ tb->pc == *pc &&
+ tb->cs_base == *cs_base &&
+ tb->flags == *flags &&
+ tb->trace_vcpu_dstate == *cpu->trace_dstate)) {
I'll just mention something I noticed while looking at perf data for Alpha.
It's a tiny thing, however: we should order these by likelyhood of mismatch.
Almost no targets really use cs_base. X86 won't use it when in a 32-bit or
64-bit flat address space. Sparc stuffs NPC into cs_base, but you really have
to explore the limits of branch delay slots in order to see NPC != PC + 4, so
NPC very rarely differs when PC is equal. Similarly for HPPA.
Which suggests checking flags before cs_base.
That said, I've also considered rewriting this without short-circuit ands
(after verifying TB != NULL) so that the compiler is free to perform all of the
subsequent loads early.
That said, this is correct as-is.
Reviewed-by: Richard Henderson <r...@twiddle.net>
r~
