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| author | Aurelien Jarno <aurelien@aurel32.net> | 2012-10-09 21:53:08 +0200 |
|---|---|---|
| committer | Aurelien Jarno <aurelien@aurel32.net> | 2012-10-28 14:54:23 +0100 |
| commit | 78505279665e64d28e4a308818b69e6f77ecc5d2 (patch) | |
| tree | 92a449ff75f77f4dcc04b5705a50beaa851c0a76 /tcg/README | |
| parent | 3d5c5f876d171983d614925eebe4f0edccbb75be (diff) | |
| download | qemu-78505279665e64d28e4a308818b69e6f77ecc5d2.tar.gz qemu-78505279665e64d28e4a308818b69e6f77ecc5d2.tar.bz2 qemu-78505279665e64d28e4a308818b69e6f77ecc5d2.zip | |
tcg: rework TCG helper flags
The current helper flags, TCG_CALL_CONST and TCG_CALL_PURE might be
confusing and doesn't provide enough granularity for some helpers (FP
helpers for example).
This patch changes them into the following helpers flags:
- TCG_CALL_NO_READ_GLOBALS means that the helper does not read globals,
either directly or via an exception. They will not be saved to their
canonical location before calling the helper.
- TCG_CALL_NO_WRITE_GLOBALS means that the helper does not modify any
globals. They will only be saved to their canonical locations before
calling helpers, but they won't be reloaded afterwise.
- TCG_CALL_NO_SIDE_EFFECTS means that the call to the function is
removed if the return value is not used.
It provides convenience flags, to avoid helper definitions longer than
80 characters. It also provides compatibility flags, and updates the
documentation.
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Diffstat (limited to 'tcg/README')
| -rw-r--r-- | tcg/README | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/tcg/README b/tcg/README index 9d1b100613..ec1ac79375 100644 --- a/tcg/README +++ b/tcg/README @@ -77,11 +77,20 @@ destroyed, but local temporaries and globals are preserved. Using the tcg_gen_helper_x_y it is possible to call any function taking i32, i64 or pointer types. By default, before calling a helper, all globals are stored at their canonical location and it is assumed -that the function can modify them. This can be overridden by the -TCG_CALL_CONST function modifier. By default, the helper is allowed to -modify the CPU state or raise an exception. This can be overridden by -the TCG_CALL_PURE function modifier, in which case the call to the -function is removed if the return value is not used. +that the function can modify them. By default, the helper is allowed to +modify the CPU state or raise an exception. + +This can be overridden using the following function modifiers: +- TCG_CALL_NO_READ_GLOBALS means that the helper does not read globals, + either directly or via an exception. They will not be saved to their + canonical locations before calling the helper. +- TCG_CALL_NO_WRITE_GLOBALS means that the helper does not modify any globals. + They will only be saved to their canonical location before calling helpers, + but they won't be reloaded afterwise. +- TCG_CALL_NO_SIDE_EFFECTS means that the call to the function is removed if + the return value is not used. + +Note that TCG_CALL_NO_READ_GLOBALS implies TCG_CALL_NO_WRITE_GLOBALS. On some TCG targets (e.g. x86), several calling conventions are supported. |