DAG arguments can optionally be named:
(dag node, node:$name)
With this change, the node is also optional:
(dag node, node:$name, $name)
The missing node is treated as an UnsetInit, so the above is equivalent
to:
(dag node, node:$name, ?:$name)
This syntax is useful in output patterns where we currently require the
types of variables to be repeated:
def : Pat<(subc i32:$b, i32:$c), (SUBCCrr i32:$b, i32:$c)>;
This is preferable:
def : Pat<(subc i32:$b, i32:$c), (SUBCCrr $b, $c)>;
llvm-svn: 177843
My "excuse" for not refactoring the grammar here is to not diverge too
far from the grammar in the comments of TGParser.cpp, since I'm not
taking on the quest of majorly refactoring TGParser.cpp at the moment.
One benefit of doing this is that Ideas for refactoring and clarifying
the grammar in this document should translate almost immediately to
beneficial refactorings that can be made to TGParser.cpp.
llvm-svn: 174144
