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<div style="font-family: Calibri, sans-serif; font-size: 14px;">Thanks to you both. </div>
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<div style="font-family: Calibri, sans-serif; font-size: 14px;">On my Linux (centos6) system, I have reproduce a variant of the bug and learned about </div>
<div style="font-family: Calibri, sans-serif; font-size: 14px;"> -plugin-opt=-debug-pass=Arguments</div>
<div style="font-family: Calibri, sans-serif; font-size: 14px;">which I infer from comments is intended to built arguments to “opt” however I found that some of the arguments don’t seem to be quite correct. I assume this just minor bit rot. </div>
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<div><font face="Consolas"> bin/opt -o pass1.bc -datalayout -notti -basictti -x86tti -targetlibinfo -no-aa -tbaa -scoped-noalias -assumption-tracker -basicaa -verify -verify-di -ipsccp -globalopt -c\</font></div>
<div><font face="Consolas">onstmerge -deadargelim -instcombine -basiccg -inline-cost -inline -prune-eh -globalopt -globaldce -basiccg -argpromotion -instcombine -lazy-value-info -jump-threading -domt\</font></div>
<div><font face="Consolas">ree -sroa -basiccg -functionattrs -globalsmodref-aa -domtree -loops -loop-simplify -lcssa -licm -memdep -mldst-motion -domtree -memdep -gvn -memdep -memcpyopt -dse -loops -\</font></div>
<div><font face="Consolas">scalar-evolution -loop-simplify -lcssa -indvars -loop-deletion -branch-prob -block-freq -loop-vectorize -scalar-evolution -alignment-from-assumptions -instcombine -lazy-val\</font></div>
<div><font face="Consolas">ue-info -jump-threading -simplifycfg -globaldce -verify -verify-di bug17623a.o</font></div>
<div><font face="Consolas">opt: Unknown command line argument '-basictti'. Try: 'bin/opt -help'</font></div>
<div><font face="Consolas">opt: Did you mean '-basiccg'?</font></div>
<div><font face="Consolas">opt: Unknown command line argument '-x86tti'. Try: 'bin/opt -help'</font></div>
<div><font face="Consolas">opt: Did you mean '-notti'?</font></div>
<div><font face="Consolas">opt: Unknown command line argument '-verify-di'. Try: 'bin/opt -help'</font></div>
<div><font face="Consolas">opt: Did you mean '-verify'?</font></div>
<div><font face="Consolas">opt: Unknown command line argument '-verify-di'. Try: 'bin/opt -help'</font></div>
<div><font face="Consolas">opt: Did you mean '-verify'?</font></div>
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<div style="font-family: Calibri, sans-serif; font-size: 14px;">On 1/5/15, 1:16 PM, "Duncan P. N. Exon Smith" <<a href="mailto:dexonsmith@apple.com">dexonsmith@apple.com</a>> wrote:</div>
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<div>On 2015-Jan-05, at 01:14, Bill Wendling <<a href="mailto:isanbard@gmail.com">isanbard@gmail.com</a>> wrote:</div>
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<div>On Jan 3, 2015, at 11:52 PM, Bill Wendling <<a href="mailto:isanbard@gmail.com">isanbard@gmail.com</a>> wrote:</div>
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<div>On Jan 2, 2015, at 8:32 PM, David Callahan <<a href="mailto:dcallahan@fb.com">dcallahan@fb.com</a>> wrote:</div>
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<div>Hi,</div>
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<div>I am new to the LLVM dev community so forgive a perhaps obvious question. I am looking at bug 17623 which is an LTO/optimizer interaction bug. I am working on a Mac with Xcode installed but have also built the 3.6 LLVM binaries (from a few month old local
branch).</div>
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<div>The default version of “ld” from Apple supports an option “-save-temps” which I believe saves bitcode both before and after the optimizer (and the bug is visible as a difference between these two)</div>
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<div>~/llvm-install/bin/clang -flto -O2 -c -o bug17623.o bug17623.c</div>
<div>"/usr/bin/ld" -demangle -dynamic -arch x86_64 -macosx_version_min 10.10.0 -lSystem /Users/dcallahan/llvm-install/bin/..\</div>
<div>/lib/clang/3.6.0/lib/darwin/libclang_rt.osx.a -save-temps -o bug36 bug17623.o</div>
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<div>(this produces bug36.lto.bc and bug36.lto.opt.bc)</div>
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<div>However, if I use “opt” to try and duplicate the actions run by “ld”, as in:</div>
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<div>~/llvm-install/bin/opt -O2 -o bug36.opt.bc bug36.lto.bc</div>
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<div>This generates a different (much cleaner and correct!) output.</div>
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<div>So my questions are:</div>
<div>1. Is it feasible to get “opt” to reproduce the behavior of “ld”?</div>
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<div>The optimizations that occur during LTO (the ‘ld’ command) are different from the “normal” optimizations that opt runs. For one, LLVM has a view of the whole program, not just one compilation unit at a time. If you want to look at some of the optimizations
that it performs, you can use the “opt -std-link-opts” command.</div>
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<div>2. Assuming I am just missing some parameters to “opt”, how do I determine what they should be?</div>
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<div>The link time optimizations are enabled via the "-std-link-opts” option.</div>
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<div>You might also need to add `-internalize-public-api-list` to prevent</div>
<div>functions like `main()` from getting internalized (and dead-stripped).</div>
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<div>I forgot to mention that you will need to link all of the .bc files together using 'llvm-link’ before you run ‘opt -std-link-opts’ on it.</div>
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<div>(If you're starting from bug36.lto.bc then they've already been linked.)</div>
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