[cfe-dev] Strange default optimization passes

Chris Lattner clattner at apple.com
Fri Sep 18 15:03:43 PDT 2009


On Sep 8, 2009, at 6:49 PM, Eli Friedman wrote:

> I just noticed when looking at some code in clang that at -O3, we run
> scalarrepl, then run mem2reg almost immediately afterwards.  I don't
> think this is intentional, but I'm not exactly sure how we ended up in
> the current situation.

Fixed in r82291, thanks Eli!

-Chris

>
> For reference, output from -debug-pass=Arguments for a file with a
> single function:
> Pass Arguments:  -preverify -domtree -verify -simplifycfg -domtree
> -domfrontier -scalarrepl -instcombine
> Pass Arguments:  -raiseallocs -simplifycfg -domtree -domfrontier
> -mem2reg -globalopt -globaldce -ipconstprop -deadargelim -instcombine
> -simplifycfg -basiccg -prune-eh -functionattrs -inline -argpromotion
> -simplify-libcalls -instcombine -jump-threading -simplifycfg -domtree
> -domfrontier -scalarrepl -instcombine -break-crit-edges -condprop
> -tailcallelim -simplifycfg -reassociate -domtree -loops -loopsimplify
> -domfrontier -lcssa -loop-rotate -licm -lcssa -loop-unswitch
> -instcombine -scalar-evolution -lcssa -iv-users -indvars
> -loop-deletion -lcssa -loop-unroll -instcombine -memdep -gvn -memdep
> -memcpyopt -sccp -instcombine -break-crit-edges -condprop -domtree
> -memdep -dse -adce -simplifycfg -strip-dead-prototypes
> -print-used-types -deadtypeelim -constmerge -print-module
>
> -Eli
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