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Diffstat (limited to 'docs/TableGenFundamentals.rst')
| -rw-r--r-- | docs/TableGenFundamentals.rst | 37 |
1 files changed, 19 insertions, 18 deletions
diff --git a/docs/TableGenFundamentals.rst b/docs/TableGenFundamentals.rst index bfb2618..4fe4bb9 100644 --- a/docs/TableGenFundamentals.rst +++ b/docs/TableGenFundamentals.rst @@ -1,5 +1,3 @@ -.. _tablegen: - ===================== TableGen Fundamentals ===================== @@ -120,16 +118,16 @@ this (at the time of this writing): } ... -This definition corresponds to a 32-bit register-register add instruction in the -X86. The string after the '``def``' string indicates the name of the -record---"``ADD32rr``" in this case---and the comment at the end of the line -indicates the superclasses of the definition. The body of the record contains -all of the data that TableGen assembled for the record, indicating that the -instruction is part of the "X86" namespace, the pattern indicating how the the -instruction should be emitted into the assembly file, that it is a two-address -instruction, has a particular encoding, etc. The contents and semantics of the -information in the record is specific to the needs of the X86 backend, and is -only shown as an example. +This definition corresponds to the 32-bit register-register ``add`` instruction +of the x86 architecture. ``def ADD32rr`` defines a record named +``ADD32rr``, and the comment at the end of the line indicates the superclasses +of the definition. The body of the record contains all of the data that +TableGen assembled for the record, indicating that the instruction is part of +the "X86" namespace, the pattern indicating how the instruction should be +emitted into the assembly file, that it is a two-address instruction, has a +particular encoding, etc. The contents and semantics of the information in the +record are specific to the needs of the X86 backend, and are only shown as an +example. As you can see, a lot of information is needed for every instruction supported by the code generator, and specifying it all manually would be unmaintainable, @@ -152,13 +150,12 @@ factor out the common features that instructions of its class share. A key feature of TableGen is that it allows the end-user to define the abstractions they prefer to use when describing their information. -Each def record has a special entry called "``NAME``." This is the name of the -def ("``ADD32rr``" above). In the general case def names can be formed from -various kinds of string processing expressions and ``NAME`` resolves to the +Each ``def`` record has a special entry called "NAME". This is the name of the +record ("``ADD32rr``" above). In the general case ``def`` names can be formed +from various kinds of string processing expressions and ``NAME`` resolves to the final value obtained after resolving all of those expressions. The user may -refer to ``NAME`` anywhere she desires to use the ultimate name of the def. -``NAME`` should not be defined anywhere else in user code to avoid conflict -problems. +refer to ``NAME`` anywhere she desires to use the ultimate name of the ``def``. +``NAME`` should not be defined anywhere else in user code to avoid conflicts. Running TableGen ---------------- @@ -794,6 +791,10 @@ Expressions used by code generator to describe instructions and isel patterns: TableGen backends ================= +Until we get a step-by-step HowTo for writing TableGen backends, you can at +least grab the boilerplate (build system, new files, etc.) from Clang's +r173931. + TODO: How they work, how to write one. This section should not contain details about any particular backend, except maybe ``-print-enums`` as an example. This should highlight the APIs in ``TableGen/Record.h``. |
