[llvm-commits] [llvm] r142530 - in /llvm/trunk: lib/Target/ARM/ARMISelLowering.cpp test/CodeGen/ARM/2011-10-18-DisableMovtSize.ll

[Evan Cheng]

On Oct 26, 2011, at 1:26 PM, Rafael Ávila de Espíndola wrote:

>> I think we just want another attribute, just like OptimizeForSize but
>> the Oz variant.  Maybe OptimizeForSizeHarder ;-)
> 
> Do you have an example or two of things that should go in 
> OptimizeForSize or OptimizeForSizeHarder?
> 
> I find the current description of -Os a bit hard to understand. If it 
> introduces no performance regression, why it is not in -O2?

> 
> A quick look a the code suggest that we could says that -Os is supposed 
> to limit passes that can introduce code bloat like inlining or tail 
> duplication. It should not be used for introducing tradeoffs in codegen. 
> In summary, "don't bloat the code to make it faster".
> 
> The decisions for using slower but smaller code would go to -Oz.
> 
> Does this sound like a correct description?

This is the correct description.

Evan

> 
>> -Chris
> 
> Cheers,
> Rafael
> 
> 
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