[llvm-commits] [PATCH] Add Pattern ID Information

[David A. Greene]

Chris Lattner <clattner at apple.com> writes:

>> Because sometimes multiple patterns map to an instruction.  Think of
>> Pat<> patterns.  It's helpful to know which pattern matched to generate
>> the instruction.
>
> I guess I don't see the value in distinguishing which of several
> possible Pat<> patterns matched a specific instruction.  If you need
> that level of detail, you'll be looking at dag dumps anyway.

DAG dumps are often very large and unwieldy, to the point of being
unreadable.  This information gives a very quick idea of how a
particular instruction got generated.  That is invaluable when tracking
down bugs.

                                -Dave