[LLVMdev] local variable in Pattern definition?

[Adam Nemet]

> On Feb 18, 2015, at 9:46 AM, Tom Stellard <tom at stellard.net> wrote:
> 
> On Wed, Feb 18, 2015 at 11:44:12AM -0500, kewuzhang wrote:
>> Hi guys, 
>> 
>> When I am trying to define  pattern in a multi class,  I got something like this:
>> “
>> multi class P_PAT<string sty, SDNode tNode>
>> {
>> 	def : Pat<( !cast<ValueType>(“v2” # sty)        (tNode !cast<ValueType>(“v2” # sty):$src1,  !cast<ValueType>(“v2” # sty):$src2) ),
>> 										( add   !cast<ValueType>(“v2” # sty):$src1,  !cast<ValueType>(“v2” # sty):$src2) >;
>> }
>> “
>> noticed that in the above pattern, the "!cast<ValueType>(“v2” # sty)” is used several times,  make the pattern looks so complicated.
>> Is there anyway to define a “local variable” so I can define it only once and use it?
>> 
> 
> Try something like this: 
> 
> multi class P_PAT<string sty, SDNode tNode, ValueType vt = !cast<ValueType>(“v2” # sty)> {
> 
> ...
> 
> }

Neat!

> 
> 
> Alternatively, you could create a class that wraps the pattern to simplify it.  For example:
> 
> class MyPat <ValueType vt, SDNode tNode> : Pat <
>  ...
>> ;
> 
> multiclass P_PAT<string sty, SDNode tNode> {
>  def : MyPat<!Cast<ValueType>("v2" # sty), sty>;
> }
> 
> -Tom
> 
>> like to make the above definition to something like:
>> "multi class P_PAT<string sty, SDNode tNode>
>> {
>> 	ValueType tt = !cast<ValueType>(“v2” # sty);  
>> 	def : Pat<( tt       (tNode tt:$src1,  tt:$src2) ),
>> 				  ( add   tt:$src1,  tt:$src2) >;
>> }
>> “
>> where the "ValueType tt = !cast<ValueType>(“v2” # sty); “ is the local variable definition,  but is sure generate compiling errors.
>> how to fix it?
>> 
>> Best
>> 
>> kevin
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> 
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