如何查看LLVM選項使用哪些優化傳遞？

Question

我想了解和修改用於不同硬件架構的LLVM opt中使用的通道。

Answer 1

假設你正在使用鐺，使用-debug通=參數選項，看看有什麼通行證被在每個優化級別運行

Answer 2

opt可以告訴你哪些通過它在給定的一段LLVM IR的運行：

$ opt -O2 -debug-pass=Arguments example_file.ll -disable-output 
Pass Arguments: -tti -no-aa -tbaa -scoped-noalias -assumption-cache-tracker -targetlibinfo -basicaa -verify -simplifycfg -domtree -sroa -early-cse -lower-expect 
Pass Arguments: -targetlibinfo -tti -no-aa -tbaa -scoped-noalias -assumption-cache-tracker -basicaa -ipsccp -globalopt -deadargelim -domtree -instcombine -simplifycfg -basiccg -prune-eh -inline-cost -inline -functionattrs -domtree -sroa -early-cse -lazy-value-info -jump-threading -correlated-propagation -simplifycfg -domtree -instcombine -tailcallelim -simplifycfg -reassociate -domtree -loops -loop-simplify -lcssa -loop-rotate -licm -loop-unswitch -instcombine -scalar-evolution -loop-simplify -lcssa -indvars -loop-idiom -loop-deletion -loop-unroll -mldst-motion -domtree -memdep -gvn -memdep -memcpyopt -sccp -domtree -bdce -instcombine -lazy-value-info -jump-threading -correlated-propagation -domtree -memdep -dse -loops -loop-simplify -lcssa -licm -adce -simplifycfg -domtree -instcombine -barrier -float2int -domtree -loops -loop-simplify -lcssa -loop-rotate -branch-prob -block-freq -scalar-evolution -loop-accesses -loop-vectorize -instcombine -scalar-evolution -slp-vectorizer -simplifycfg -domtree -instcombine -loops -loop-simplify -lcssa -scalar-evolution -loop-unroll -instcombine -loop-simplify -lcssa -licm -scalar-evolution -alignment-from-assumptions -strip-dead-prototypes -elim-avail-extern -globaldce -constmerge -verify 

查看源代碼，這是一般的問題：

實例化PassManagerBuilder並調用SetOptLevel。 建造者然後adds the passes as part of populateModulePassManager。

請注意，the default pass orderings have been tuned for C/C++並不一定適用於其他語言。