[llvm-dev] [RFC] Disabling DAG combines in /O0

Krzysztof Parzyszek via llvm-dev llvm-dev at lists.llvm.org
Tue May 17 06:25:13 PDT 2016

On 5/16/2016 8:36 PM, Quentin Colombet via llvm-dev wrote:
> DAG combiner does indeed optimizations but also canonicalization.

This has been discussed before and AFAIR, the problem is that the exact 
handshakes between combining and legalization are not documented. A 
specification of the canonical forms during various stages of 
legalization would make it much easier to decouple canonicalization from 

Also, do we know that the required canonicalization will not have the 
same problem as the combining?  That is, whether the necessary 
canonicalization steps will not affect the "debuggability" of the program?


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