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tcg: Document tcg_qemu_tb_exec() and provide constants for low bit uses

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Document tcg_qemu_tb_exec(). In particular, its return value is a
combination of a pointer to the next translation block and some
extra information in the low two bits. Provide some #defines for
the values passed in these bits to improve code clarity.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
This commit is contained in:
Peter Maydell 2013-02-22 18:10:00 +00:00 • committed by Blue Swirl
parent 07ca08bac8
commit 0980011b4f
3 changed files with 49 additions and 6 deletions
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9
cpu-exec.c
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@ -72,7 +72,7 @@ static void cpu_exec_nocache(CPUArchState *env, int max_cycles,
next_tb = tcg_qemu_tb_exec(env, tb->tc_ptr);
cpu->current_tb = NULL;
if ((next_tb & 3) == 2) {
if ((next_tb & TB_EXIT_MASK) == TB_EXIT_ICOUNT_EXPIRED) {
/* Restore PC. This may happen if async event occurs before
the TB starts executing. */
cpu_pc_from_tb(env, tb);
@ -584,7 +584,8 @@ int cpu_exec(CPUArchState *env)
spans two pages, we cannot safely do a direct
jump. */
if (next_tb != 0 && tb->page_addr[1] == -1) {
tb_add_jump((TranslationBlock *)(next_tb & ~3), next_tb & 3, tb);
tb_add_jump((TranslationBlock *)(next_tb & ~TB_EXIT_MASK),
next_tb & TB_EXIT_MASK, tb);
}
spin_unlock(&tcg_ctx.tb_ctx.tb_lock);
@ -598,10 +599,10 @@ int cpu_exec(CPUArchState *env)
tc_ptr = tb->tc_ptr;
/* execute the generated code */
next_tb = tcg_qemu_tb_exec(env, tc_ptr);
if ((next_tb & 3) == 2) {
if ((next_tb & TB_EXIT_MASK) == TB_EXIT_ICOUNT_EXPIRED) {
/* Instruction counter expired. */
int insns_left;
tb = (TranslationBlock *)(next_tb & ~3);
tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
/* Restore PC. */
cpu_pc_from_tb(env, tb);
insns_left = env->icount_decr.u32;