This is the payoff. >From perf record -g data of ubuntu 18 boot and shutdown:
BEFORE: - 23.02% 2.82% qemu-system-aar [.] helper_lookup_tb_ptr - 20.22% helper_lookup_tb_ptr + 10.05% tb_htable_lookup - 9.13% cpu_get_tb_cpu_state 3.20% aa64_va_parameters_both 0.55% fp_exception_el - 11.66% 4.74% qemu-system-aar [.] cpu_get_tb_cpu_state - 6.96% cpu_get_tb_cpu_state 3.63% aa64_va_parameters_both 0.60% fp_exception_el 0.53% sve_exception_el AFTER: - 16.40% 3.40% qemu-system-aar [.] helper_lookup_tb_ptr - 13.03% helper_lookup_tb_ptr + 11.19% tb_htable_lookup 0.55% cpu_get_tb_cpu_state 0.98% 0.71% qemu-system-aar [.] cpu_get_tb_cpu_state 0.87% 0.24% qemu-system-aar [.] rebuild_hflags_a64 Before, helper_lookup_tb_ptr is the second hottest function in the application, consuming almost a quarter of the runtime. Within the entire execution, cpu_get_tb_cpu_state consumes about 12%. After, helper_lookup_tb_ptr has dropped to the fourth hottest function, with consumption dropping to a sixth of the runtime. Within the entire execution, cpu_get_tb_cpu_state has dropped below 1%, and the supporting function to rebuild hflags also consumes about 1%. Signed-off-by: Richard Henderson <richard.hender...@linaro.org> --- target/arm/helper.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/target/arm/helper.c b/target/arm/helper.c index 3c8724883d..1bdb87267e 100644 --- a/target/arm/helper.c +++ b/target/arm/helper.c @@ -13894,21 +13894,16 @@ void HELPER(rebuild_hflags_a64)(CPUARMState *env, uint32_t el) void cpu_get_tb_cpu_state(CPUARMState *env, target_ulong *pc, target_ulong *cs_base, uint32_t *pflags) { - int current_el = arm_current_el(env); - uint32_t flags; + uint32_t flags = env->hflags; uint32_t pstate_for_ss; *cs_base = 0; - if (is_a64(env)) { + if (FIELD_EX32(flags, TBFLAG_ANY, AARCH64_STATE)) { *pc = env->pc; - flags = rebuild_hflags_a64(env, current_el); - assert(flags == env->hflags); flags = FIELD_DP32(flags, TBFLAG_A64, BTYPE, env->btype); pstate_for_ss = env->pstate; } else { *pc = env->regs[15]; - flags = rebuild_hflags_a32(env, current_el); - assert(flags == env->hflags); flags = FIELD_DP32(flags, TBFLAG_A32, THUMB, env->thumb); flags = FIELD_DP32(flags, TBFLAG_A32, CONDEXEC, env->condexec_bits); pstate_for_ss = env->uncached_cpsr; -- 2.17.1