[llvm-dev] optimization remarks

[Friedman, Eli via llvm-dev]

On 8/14/2018 6:57 AM, Jonas Paulsson via llvm-dev wrote:
> Hi,
>
> I am trying to compare the loop vectorizers effectiveness for 
> different targets relative to each other. That way, I am hoping to 
> find loops that are not vectorized - but could be - on my target by 
> finding other targets doing this successfully. With some luck, there 
> might be something in the Target files that could be fixed with 
> improved vectorization as a result...
>
> I would like to do this with the optimization remarks enabled: 
> -Rpass=loop-vectorize, etc. Since cross-compiling benchmarks seems 
> tricky to me at the moment, my idea was to first run the front end, 
> and then run the optimizers for different targets. However, when I 
> pass -save-temps to clang there are no remarks emitted at all any 
> more... So in effect I can only get the remarks for the target I am on 
> :-/
>
> I wonder if there is a reason for this, or if it's something that 
> could be fixed?
>

I think it's just a bug; if you pass -### to clang, you can see how 
-save-temps actually invokes clang four times, and -Rpass only gets 
passed to the first invocation.

-Eli

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