On 09/18/2015 06:08 AM, Peter Maydell wrote:
On 18 September 2015 at 05:55, Richard Henderson <r...@twiddle.net> wrote:
We can now restore state without retranslation.
Signed-off-by: Richard Henderson <r...@twiddle.net>
---
+/* Encode the data collected about the instructions while compiling TB.
+ Place the data at BLOCK, and return the number of bytes consumed.
+
+ The logical table consisits of TARGET_INSN_START_WORDS target_ulong's,
"consists". No apostrophe in 'target_ulongs'.
+ which come from the target's insn_start data, followed by a uintptr_t
+ which comes from the host pc of the end of the code implementing the insn.
+
+ Each line of the table is encoded as sleb128 deltas from the previous
+ line. The seed for the first line is { tb->pc, 0..., tb->tc_ptr }.
+ That is, the first column is seeded with the guest pc, the last column
+ with the host pc, and the middle columns with zeros. */
You're still not allowing for your worst-case datatable size when we
calculate tcg_ctx.code_gen_buffer_max_size.
I'll note that the current worst-case estimate is way too big: 122kB.
Which honestly means we're wasting a ton of space at the end of the
code_gen_buffer. While down-thread we talk about guard pages and sigsegv
handlers etc, I now believe this shouldn't be a blocker for this patch set.
(And in particular, setting up a SEH handler for Win32 to act as a sigsegv
handler is just too annoyingly difficult. It'd be one thing if we only
targeted VC++, but doing SEH in GCC at present is just Too Ugly. So we'd have
two different schemes for win32 and posix, which doesn't seem to be the best of
ideas.)
r~
