[llvm-commits] [llvm] r121905 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineCompares.cpp test/Transforms/InstCombine/overflow.ll

[Chris Lattner]

On Dec 15, 2010, at 3:02 PM, Alistair Lynn wrote:

> Hi Owen-
> 
> If these patterns can be matched automatically, would it not be better to do the matching in the DAG combiner and get rid of the intrinsics?

We prefer to do matching at the mid-level when possible, not at codegen level (see also bswap).  Doing this *just* in dag combine would miss cases that require cross block patterns, and would make it difficult to implement CSE of "add with overflow(x,y)" with "add(x,y)" which hopefully GVN will catch in the future.

-Chris