[PATCH] D145586: [AMDGPU] Tweak PromoteAlloca limits

[Pierre van Houtryve via Phabricator via llvm-commits]

Pierre-vh added inline comments.


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Comment at: llvm/lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp:181
-    MaxVGPRs = ST.getMaxNumVGPRs(ST.getWavesPerEU(F).first);
-    // A non-entry function has only 32 caller preserved registers.
-    // Do not promote alloca which will force spilling.
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rampitec wrote:
> arsenm wrote:
> > rampitec wrote:
> > > Isn't this still true? You might not see alloca, but you will see spills.
> > Trading spills inside a function for CSR spills can be profitable, such as if the spilling occurs in a loop.
> > 
> > IIRC this was to workaround some compile failures 
> One reason for the current limits were 'run of registers' errors in some cases. I'd be really careful extending the limits.
I would be okay with leaving the limit at 1/4 (or raising it to 1/3 instead of 1/2), as long as the entry function CC exception is removed. That should be enough for the particular case I'm interested in.


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  https://reviews.llvm.org/D145586/new/

https://reviews.llvm.org/D145586