diff options
Diffstat (limited to 'llvm/docs/TableGen/LangRef.rst')
| -rw-r--r-- | llvm/docs/TableGen/LangRef.rst | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/llvm/docs/TableGen/LangRef.rst b/llvm/docs/TableGen/LangRef.rst index 7cbe6d99643..74af1ee659f 100644 --- a/llvm/docs/TableGen/LangRef.rst +++ b/llvm/docs/TableGen/LangRef.rst @@ -89,6 +89,7 @@ TableGen also has the following keywords:: bit bits class code dag def foreach defm field in int let list multiclass string + if then else TableGen also has "bang operators" which have a wide variety of meanings: @@ -125,7 +126,7 @@ TableGen's top-level production consists of "objects". .. productionlist:: TableGenFile: `Object`* Object: `Class` | `Def` | `Defm` | `Defset` | `Defvar` | `Let` | - `MultiClass` | `Foreach` + `MultiClass` | `Foreach` | `If` ``class``\es ------------ @@ -466,6 +467,24 @@ iterated value. Note that the productions involving RangeList and RangePiece have precedence over the more generic value parsing based on the first token. +``if`` +------ + +.. productionlist:: + If: "if" `Value` "then" `IfBody` + :| "if" `Value` "then" `IfBody` "else" `IfBody` + IfBody: "{" `Object`* "}" | `Object` + +The value expression after the ``if`` keyword is evaluated, and if it evaluates +to true (in the same sense used by the ``!if`` operator), then the object +definition(s) after the ``then`` keyword are executed. Otherwise, if there is +an ``else`` keyword, the definition(s) after the ``else`` are executed instead. + +Because the braces around the ``then`` clause are optional, this grammar rule +has the usual ambiguity about dangling ``else`` clauses, and it is resolved in +the usual way: in a case like ``if v1 then if v2 then {...} else {...}``, the +``else`` binds to the inner ``if`` rather than the outer one. + Top-Level ``let`` ----------------- |
