[PATCH] D145210: [Pipeline] Adjust PostOrderFunctionAttrs placement in simplification pipeline

[Arthur Eubanks via Phabricator via llvm-commits]

aeubanks added inline comments.


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Comment at: llvm/lib/Passes/PassBuilderPipelines.cpp:838
+  // functions.
+  MainCGPipeline.addPass(PostOrderFunctionAttrsPass(/*SkipNonRecursive*/ true));
 
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cfang wrote:
> We found that "nofree" attribute will greatly affect the earlyCSE pass in function simplification. In our case, missing nofree essentially disabled earlyCSE which resulted in a huge performance regression (register pressure).   Other optimizations like GVN in function simplification may also be affected by function attributes.
> 
> So is it possible that we just run this pass twice?   Thanks.
Can you give an example where EarlyCSE depends on function attributes? That doesn't really make sense to me, function attributes should really be used by callers of the function, not the function itself.


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https://reviews.llvm.org/D145210