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authorSergey Fedorov <serge.fdrv@gmail.com>2016-04-21 15:58:23 +0300
committerRichard Henderson <rth@twiddle.net>2016-05-12 14:06:42 -1000
commit819af24b9c1e95e6576f1cefd32f4d6bf56dfa56 (patch)
tree6088ddcf98e9610d4ac78ba8691b872d7cb762fc /tcg
parent7687bf52e5dc39215cde723bb2afb7c53b8bd842 (diff)
tcg: Clean up from 'next_tb'
The value returned from tcg_qemu_tb_exec() is the value passed to the corresponding tcg_gen_exit_tb() at translation time of the last TB attempted to execute. It is a little confusing to store it in a variable named 'next_tb'. In fact, it is a combination of 4-byte aligned pointer and additional information in its two least significant bits. Break it down right away into two variables named 'last_tb' and 'tb_exit' which are a pointer to the last TB attempted to execute and the TB exit reason, correspondingly. This simplifies the code and improves its readability. Correct a misleading documentation comment for tcg_qemu_tb_exec() and fix logging in cpu_tb_exec(). Also rename a misleading 'next_tb' in another couple of places. Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> Signed-off-by: Richard Henderson <rth@twiddle.net>
Diffstat (limited to 'tcg')
-rw-r--r--tcg/tcg.h19
1 files changed, 10 insertions, 9 deletions
diff --git a/tcg/tcg.h b/tcg/tcg.h
index 0fceef5333..a013d77a33 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -925,7 +925,7 @@ static inline unsigned get_mmuidx(TCGMemOpIdx oi)
/**
* tcg_qemu_tb_exec:
- * @env: CPUArchState * for the CPU
+ * @env: pointer to CPUArchState for the CPU
* @tb_ptr: address of generated code for the TB to execute
*
* Start executing code from a given translation block.
@@ -936,30 +936,31 @@ static inline unsigned get_mmuidx(TCGMemOpIdx oi)
* which has not yet been directly linked, or an asynchronous
* event such as an interrupt needs handling.
*
- * The return value is a pointer to the next TB to execute
- * (if known; otherwise zero). This pointer is assumed to be
- * 4-aligned, and the bottom two bits are used to return further
- * information:
+ * Return: The return value is the value passed to the corresponding
+ * tcg_gen_exit_tb() at translation time of the last TB attempted to execute.
+ * The value is either zero or a 4-byte aligned pointer to that TB combined
+ * with additional information in its two least significant bits. The
+ * additional information is encoded as follows:
* 0, 1: the link between this TB and the next is via the specified
* TB index (0 or 1). That is, we left the TB via (the equivalent
* of) "goto_tb <index>". The main loop uses this to determine
* how to link the TB just executed to the next.
* 2: we are using instruction counting code generation, and we
* did not start executing this TB because the instruction counter
- * would hit zero midway through it. In this case the next-TB pointer
+ * would hit zero midway through it. In this case the pointer
* returned is the TB we were about to execute, and the caller must
* arrange to execute the remaining count of instructions.
* 3: we stopped because the CPU's exit_request flag was set
* (usually meaning that there is an interrupt that needs to be
- * handled). The next-TB pointer returned is the TB we were
- * about to execute when we noticed the pending exit request.
+ * handled). The pointer returned is the TB we were about to execute
+ * when we noticed the pending exit request.
*
* If the bottom two bits indicate an exit-via-index then the CPU
* state is correctly synchronised and ready for execution of the next
* TB (and in particular the guest PC is the address to execute next).
* Otherwise, we gave up on execution of this TB before it started, and
* the caller must fix up the CPU state by calling the CPU's
- * synchronize_from_tb() method with the next-TB pointer we return (falling
+ * synchronize_from_tb() method with the TB pointer we return (falling
* back to calling the CPU's set_pc method with tb->pb if no
* synchronize_from_tb() method exists).
*