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| author | Richard Henderson <richard.henderson@linaro.org> | 2019-07-22 17:02:56 -0700 |
|---|---|---|
| committer | Richard Henderson <richard.henderson@linaro.org> | 2019-08-19 08:03:41 -0700 |
| commit | 94597b6146f30f949f2c454f424082a2b0f55a0e (patch) | |
| tree | 5436bccd14b058534d76aa5e0999d54c678bbe3c /docs | |
| parent | 3fbd3405d2b0604ea530fc7a1828f19da1e95ff9 (diff) | |
| download | qemu-94597b6146f30f949f2c454f424082a2b0f55a0e.zip qemu-94597b6146f30f949f2c454f424082a2b0f55a0e.tar.gz qemu-94597b6146f30f949f2c454f424082a2b0f55a0e.tar.bz2 | |
decodetree: Allow !function with no input bits
Call this form a "parameter", returning a value extracted
from the DisasContext.
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/devel/decodetree.rst | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/docs/devel/decodetree.rst b/docs/devel/decodetree.rst index 44ac621..ce7f523 100644 --- a/docs/devel/decodetree.rst +++ b/docs/devel/decodetree.rst @@ -23,7 +23,7 @@ Fields Syntax:: - field_def := '%' identifier ( unnamed_field )+ ( !function=identifier )? + field_def := '%' identifier ( unnamed_field )* ( !function=identifier )? unnamed_field := number ':' ( 's' ) number For *unnamed_field*, the first number is the least-significant bit position @@ -34,6 +34,12 @@ present, they are concatenated. In this way one can define disjoint fields. If ``!function`` is specified, the concatenated result is passed through the named function, taking and returning an integral value. +One may use ``!function`` with zero ``unnamed_fields``. This case is called +a *parameter*, and the named function is only passed the ``DisasContext`` +and returns an integral value extracted from there. + +A field with no ``unnamed_fields`` and no ``!function`` is in error. + FIXME: the fields of the structure into which this result will be stored is restricted to ``int``. Which means that we cannot expand 64-bit items. |