48e14066ac
Here we introduce a new compiler flag to disable the checking of exit request (icount_decr.u32). This is useful when we want to ensure the next block cannot be preempted by an asynchronous event. Suggested-by: Richard Henderson <richard.henderson@linaro.org> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Message-Id: <20211129140932.4115115-2-alex.bennee@linaro.org>
95 lines
2.9 KiB
C
95 lines
2.9 KiB
C
#ifndef GEN_ICOUNT_H
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#define GEN_ICOUNT_H
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#include "exec/exec-all.h"
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#include "qemu/timer.h"
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/* Helpers for instruction counting code generation. */
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static TCGOp *icount_start_insn;
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static inline void gen_io_start(void)
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{
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TCGv_i32 tmp = tcg_const_i32(1);
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tcg_gen_st_i32(tmp, cpu_env,
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offsetof(ArchCPU, parent_obj.can_do_io) -
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offsetof(ArchCPU, env));
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tcg_temp_free_i32(tmp);
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}
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static inline void gen_tb_start(const TranslationBlock *tb)
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{
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TCGv_i32 count;
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if (tb_cflags(tb) & CF_USE_ICOUNT) {
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count = tcg_temp_local_new_i32();
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} else {
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count = tcg_temp_new_i32();
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}
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tcg_gen_ld_i32(count, cpu_env,
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offsetof(ArchCPU, neg.icount_decr.u32) -
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offsetof(ArchCPU, env));
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if (tb_cflags(tb) & CF_USE_ICOUNT) {
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/*
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* We emit a sub with a dummy immediate argument. Keep the insn index
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* of the sub so that we later (when we know the actual insn count)
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* can update the argument with the actual insn count.
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*/
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tcg_gen_sub_i32(count, count, tcg_constant_i32(0));
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icount_start_insn = tcg_last_op();
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}
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/*
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* Emit the check against icount_decr.u32 to see if we should exit
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* unless we suppress the check with CF_NOIRQ. If we are using
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* icount and have suppressed interruption the higher level code
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* should have ensured we don't run more instructions than the
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* budget.
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*/
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if (tb_cflags(tb) & CF_NOIRQ) {
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tcg_ctx->exitreq_label = NULL;
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} else {
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tcg_ctx->exitreq_label = gen_new_label();
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tcg_gen_brcondi_i32(TCG_COND_LT, count, 0, tcg_ctx->exitreq_label);
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}
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if (tb_cflags(tb) & CF_USE_ICOUNT) {
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tcg_gen_st16_i32(count, cpu_env,
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offsetof(ArchCPU, neg.icount_decr.u16.low) -
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offsetof(ArchCPU, env));
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/*
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* cpu->can_do_io is cleared automatically here at the beginning of
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* each translation block. The cost is minimal and only paid for
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* -icount, plus it would be very easy to forget doing it in the
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* translator. Doing it here means we don't need a gen_io_end() to
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* go with gen_io_start().
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*/
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tcg_gen_st_i32(tcg_constant_i32(0), cpu_env,
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offsetof(ArchCPU, parent_obj.can_do_io) -
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offsetof(ArchCPU, env));
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}
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tcg_temp_free_i32(count);
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}
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static inline void gen_tb_end(const TranslationBlock *tb, int num_insns)
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{
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if (tb_cflags(tb) & CF_USE_ICOUNT) {
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/*
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* Update the num_insn immediate parameter now that we know
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* the actual insn count.
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*/
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tcg_set_insn_param(icount_start_insn, 2,
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tcgv_i32_arg(tcg_constant_i32(num_insns)));
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}
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if (tcg_ctx->exitreq_label) {
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gen_set_label(tcg_ctx->exitreq_label);
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tcg_gen_exit_tb(tb, TB_EXIT_REQUESTED);
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}
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}
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#endif
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