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| author | Paolo Bonzini <pbonzini@redhat.com> | 2012-10-31 10:42:51 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2012-10-31 10:42:51 +0100 |
| commit | f563a5d7a820424756f358e747238f03e866838a (patch) | |
| tree | f78fa474b1933bd395af401a6d745150f4ecd15e /tcg/README | |
| parent | a27365265cc2fed1178bf25a205e8ee02a9c0caf (diff) | |
| parent | aee0bf7d8d7564f8f2c40e4501695c492b7dd8d1 (diff) | |
Merge remote-tracking branch 'origin/master' into threadpool
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'tcg/README')
| -rw-r--r-- | tcg/README | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/tcg/README b/tcg/README index aa86992bca..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. @@ -349,6 +358,9 @@ st32_i64 t0, t1, offset write(t0, t1 + offset) Write 8, 16, 32 or 64 bits to host memory. +All this opcodes assume that the pointed host memory doesn't correspond +to a global. In the latter case the behaviour is unpredictable. + ********* 64-bit target on 32-bit host support The following opcodes are internal to TCG. Thus they are to be implemented by |