[llvm-dev] Order of LLVM Transform passes?

[Michael Kruse via llvm-dev]

Am Fr., 6. März 2020 um 10:05 Uhr schrieb Shishir V Jessu via llvm-dev
<llvm-dev at lists.llvm.org>:
> I am writing an LLVM Transform pass whose behavior may need to change depending on whether a different pass is run before or after it. How can I find out which Transform passes are run in which order when I run opt?

$ opt -debug-pass=Arguments -O3 ....

Will print the sequence of passes at the chosen level (legacy pass manager):

Pass Arguments:  -tti -tbaa -scoped-noalias -assumption-cache-tracker
-targetlibinfo -verify -ee-instrument -simplifycfg -domtree -sroa
-early-cse -lower-expect
Pass Arguments:  -targetlibinfo -tti -tbaa -scoped-noalias
-assumption-cache-tracker -profile-summary-info -forceattrs
-inferattrs -attributor -domtree -callsite-splitting -ipsccp
-called-value-propagation -globalopt -domtree -mem2reg -deadargelim
-domtree -basicaa -aa -loops -lazy-branch-prob -lazy-block-freq
-opt-remark-emitter -instcombine -simplifycfg -basiccg -globals-aa
-prune-eh -inline -attributor-cgscc -openmpopt -functionattrs
-argpromotion -domtree -sroa -basicaa -aa -memoryssa -early-cse-memssa
-speculative-execution -aa -lazy-value-info -jump-threading
-correlated-propagation -simplifycfg -domtree -aggressive-instcombine
-basicaa -aa -loops -lazy-branch-prob -lazy-block-freq
-opt-remark-emitter -instcombine -libcalls-shrinkwrap -loops
-branch-prob -block-freq -lazy-branch-prob -lazy-block-freq
-opt-remark-emitter -pgo-memop-opt -basicaa -aa -loops
-lazy-branch-prob -lazy-block-freq -opt-remark-emitter -tailcallelim
-simplifycfg -reassociate -domtree -loops -loop-simplify
-lcssa-verification -lcssa -basicaa -aa -scalar-evolution -loop-rotate
-memoryssa -licm -loop-unswitch -simplifycfg -domtree -basicaa -aa
-loops -lazy-branch-prob -lazy-block-freq -opt-remark-emitter
-instcombine -loop-simplify -lcssa-verification -lcssa
-scalar-evolution -indvars -loop-idiom -loop-deletion -loop-unroll
-mldst-motion -phi-values -aa -memdep -lazy-branch-prob
-lazy-block-freq -opt-remark-emitter -gvn -phi-values -basicaa -aa
-memdep -memcpyopt -sccp -demanded-bits -bdce -aa -lazy-branch-prob
-lazy-block-freq -opt-remark-emitter -instcombine -lazy-value-info
-jump-threading -correlated-propagation -basicaa -aa -phi-values
-memdep -dse -aa -memoryssa -loops -loop-simplify -lcssa-verification
-lcssa -scalar-evolution -licm -postdomtree -adce -simplifycfg
-domtree -basicaa -aa -loops -lazy-branch-prob -lazy-block-freq
-opt-remark-emitter -instcombine -barrier -elim-avail-extern -basiccg
-rpo-functionattrs -globalopt -globaldce -basiccg -globals-aa -domtree
-float2int -lower-constant-intrinsics -domtree -loops -loop-simplify
-lcssa-verification -lcssa -basicaa -aa -scalar-evolution -loop-rotate
-loop-accesses -lazy-branch-prob -lazy-block-freq -opt-remark-emitter
-loop-distribute -branch-prob -block-freq -scalar-evolution -basicaa
-aa -loop-accesses -demanded-bits -lazy-branch-prob -lazy-block-freq
-opt-remark-emitter -inject-tli-mappings -loop-vectorize
-loop-simplify -scalar-evolution -aa -loop-accesses -lazy-branch-prob
-lazy-block-freq -loop-load-elim -vector-combine -basicaa -aa
-lazy-branch-prob -lazy-block-freq -opt-remark-emitter -instcombine
-simplifycfg -domtree -loops -scalar-evolution -basicaa -aa
-demanded-bits -lazy-branch-prob -lazy-block-freq -opt-remark-emitter
-slp-vectorizer -vector-combine -aa -opt-remark-emitter -instcombine
-loop-simplify -lcssa-verification -lcssa -scalar-evolution
-loop-unroll -lazy-branch-prob -lazy-block-freq -opt-remark-emitter
-instcombine -memoryssa -loop-simplify -lcssa-verification -lcssa
-scalar-evolution -licm -lazy-branch-prob -lazy-block-freq
-opt-remark-emitter -transform-warning -alignment-from-assumptions
-strip-dead-prototypes -globaldce -constmerge -domtree -loops
-branch-prob -block-freq -loop-simplify -lcssa-verification -lcssa
-basicaa -aa -scalar-evolution -block-freq -loop-sink
-lazy-branch-prob -lazy-block-freq -opt-remark-emitter -instsimplify
-div-rem-pairs -simplifycfg -verify
Pass Arguments:  -domtree
Pass Arguments:  -targetlibinfo -domtree -loops -branch-prob -block-freq
Pass Arguments:  -targetlibinfo -domtree -loops -branch-prob -block-freq

With in the pass, it it difficult to determine whether another pass
changed a function. In Polly, we attach an attribute to the function
"polly-optimized" to which a cleanup-pass can react to.


> Further, I assume that Analysis passes are always run prior to Transform passes - is this correct? Thanks!

Yes, in the legacy pass manager (getAnalysisUsage tell the pass
manager which analyses to run; not that some analyses are lazy and
only determine the properties when asked for it)

No in the new pass manager. Analyses run when calling getAnalysis.

Michael