[LLVMdev] Trying out Loop Vectorizer

[Nadav Rotem]

On Dec 31, 2012, at 11:57 AM, Benjamin Kramer <benny.kra at gmail.com> wrote:

> I'm not entirely sure why this is the case, the target specific stuff for opt is still very new, but at the moment you have to explicitly set a triple for opt so it can access target-specific bits to estimate the cost of vectorization.

I think that this is a good opportunity to discuss this topic.  At the moment 'opt' does not use the triple that is found in the module in order to initialize the backend and the backend related analysis passes. It relies on the '-mtriple' command line flag. LLC on the other hand uses the host triple. I see the following options:

1. 'opt' does not initialize the backend passes unless '-mtriple' is used. (the current option)
2. 'opt' grabs the triple from the bit code file and uses it to initialize the backend passes.
3. 'opt' gets the default target triple (like llc).

I think that Nick said that he prefers #2.

Nadav 
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