[NFC][Inliner] Debugging support to print funtion size after each inlining.

[wenlei]

llvm/lib/Transforms/IPO/Inliner.cpp

842

We have debug prints for negative decision, but not positive decision, so we may end up with a bunch of "function size: ..". Would it be more helpful to say "Function size: X after inlining Y" or something like that?

[hoy]

llvm/lib/Transforms/IPO/Inliner.cpp

842

We actually have debug prints for positive decision. With the size printing, the debug log now looks like

Inlining calls in: _ZN11opentracing2v24util6detail10dispatcherIRN8facebook7tracing11opentracing12_GLOBAL__N_112ValueVisitorENS0_5ValueENSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEJDnPKcNS1_17recursive_wrapperISt6vectorISA_SaISA_EEEENSJ_ISt13unordered_mapISG_SA_St4hashISG_ESt8equal_toISG_ESaISt4pairIKSG_SA_EEEEEEE11apply_constERKSA_S9_
    Function size: 11
    Inlining (cost=always): always inline attribute, Call:   %4 = call zeroext i1 @_ZNK11opentracing2v24util7variantIJbdlmNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEDnPKcNS1_17recursive_wrapperISt6vectorINS0_5ValueESaISD_EEEENSB_ISt13unordered_mapIS8_SD_St4hashIS8_ESt8equal_toIS8_ESaISt4pairIKS8_SD_EEEEEEE2isIDnEEbv(%"class.opentracing::v2::util::variant"* nonnull %3), !dbg !35441
    Function size: 13
    Inlining (cost=always): always inline attribute, Call:   %8 = call dereferenceable(8) i8** @_ZNK11opentracing2v24util7variantIJbdlmNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEDnPKcNS1_17recursive_wrapperISt6vectorINS0_5ValueESaISD_EEEENSB_ISt13unordered_mapIS8_SD_St4hashIS8_ESt8equal_toIS8_ESaISt4pairIKS8_SD_EEEEEEE3getIDnLPv0EEERKT_v(%"class.opentracing::v2::util::variant"* nonnull %3), !dbg !35458
    Function size: 26
    Inlining (cost=-35, threshold=375), Call:   %20 = call dereferenceable(8) i8** @_ZN11opentracing2v24util6detail9unwrapperIDnE11apply_constERKDn(i8** nonnull dereferenceable(8) %19), !dbg !35486
    Function size: 25
    Inlining (cost=-15020, threshold=375), Call:   call fastcc void @_ZNK8facebook7tracing11opentracing12_GLOBAL__N_112ValueVisitorclIDnEENSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEET_(%"class.std::__cxx11::basic_string"* noalias %0), !dbg !35501
    Function size: 31
    Inlining (cost=-30, threshold=375), Call:   call fastcc void @_ZSt7forwardIRN8facebook7tracing11opentracing12_GLOBAL__N_112ValueVisitorEEOT_RNSt16remove_referenceIS6_E4typeE() #26, !dbg !35617
    Function size: 30

[hoy]

llvm/lib/Transforms/IPO/Inliner.cpp

842

Well, I think you are right. I was looking at an older version and it had debug prints for positive decision there.

[hoy]

llvm/lib/Transforms/IPO/Inliner.cpp

842

I double checked the latest code base. The inliner advisor actually prints out positive decisions (see llvm::shouldInline) and the debug output with this change will look like

Inlining calls in: foo
    Function size: 2
    Inlining (cost=25, threshold=75), Call:   call void @bar(i1 true)
    Function size: 3
Updated inlining SCC: (foo)
Inlined an internal call edge and split an SCC, retaining this to avoid infinite inlining.
Inlining calls in: foo
    Function size: 3
    NOT Inlining (cost=never): recursive, Call:   call void @foo()
Inlining calls in: foo
    Function size: 3
    NOT Inlining (cost=never): recursive, Call:   call void @foo()
Inlining calls in: bar
    Function size: 6
    NOT Inlining (cost=never): recursive, Call:   call void @foo()
    Inlining (cost=25, threshold=75), Call:   call void @bar(i1 true)
    Function size: 7
    NOT Inlining (cost=never): recursive, Call:   call void @foo()
Updated inlining SCC: (bar)
Inlining calls in: test1
    Function size: 3
    Inlining (cost=25, threshold=75), Call:   call void @bar(i1 true)
    Function size: 4
    Inlining (cost=25, threshold=75), Call:   call void @bar(i1 false)
    Function size: 5
    NOT Inlining (cost=never): recursive, Call:   call void @foo()
    NOT Inlining (cost=never): recursive, Call:   call void @foo()
Updated inlining SCC: (test1)
Inlining calls in: test2
    Function size: 3
    Inlining (cost=-30, threshold=75), Call:   call void @noop()
    Function size: 2
    Inlining (cost=-30, threshold=75), Call:   call void @noop() [ "CUSTOM_OPERAND_BUNDLE"() ]
Updated inlining SCC: (test2)
Inlining calls in: test3
    Function size: 2
    NOT Inlining (cost=never): recursive call, Call:   call void @test3() #0

[wenlei]

llvm/lib/Transforms/IPO/Inliner.cpp

842

ok, thanks for checking. nit: use "Size after inlining"? From the print out above, currently it looks more like size of the inlinee.

[hoy]

Addressing feedbacks.

llvm/lib/Transforms/IPO/Inliner.cpp

842

Sounds good.

[wenlei]

lgtm, thanks.

llvm/lib/Transforms/IPO/Inliner.cpp

for (int I = 0; I < (int)Calls.size(); ++I) {
     // have the same caller, so we first set up some shared infrastructure for
     // this caller. We also do any pruning we can at this layer on the caller
     // alone.
     Function &F = *Calls[I].first->getCaller();
     LazyCallGraph::Node &N = *CG.lookup(F);
     if (CG.lookupSCC(N) != C)
       continue;
 
-    LLVM_DEBUG(dbgs() << "Inlining calls in: " << F.getName() << "\n");
+    LLVM_DEBUG(dbgs() << "Inlining calls in: " << F.getName() << "\n"
+                      << "    Function size: " << F.getInstructionCount()
+                      << "\n");
 
     auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & {
       return FAM.getResult<AssumptionAnalysis>(F);
     };
 
     // Now process as many calls as we have within this caller in the sequence.
     // We bail out as soon as the caller has to change so we can update the
     // call graph and prepare the context of that new caller.
for (; I < (int)Calls.size() && Calls[I].first->getCaller() == &F; ++I) {
         Advice->recordUnsuccessfulInlining(IR);
         continue;
       }
 
       DidInline = true;
       InlinedCallees.insert(&Callee);
       ++NumInlined;
 
+      LLVM_DEBUG(dbgs() << "    Size after inlining: "
+                        << F.getInstructionCount() << "\n");
+
       // Add any new callsites to defined functions to the worklist.
       if (!IFI.InlinedCallSites.empty()) {
         int NewHistoryID = InlineHistory.size();
         InlineHistory.push_back({&Callee, InlineHistoryID});
 
         for (CallBase *ICB : reverse(IFI.InlinedCallSites)) {
           Function *NewCallee = ICB->getCalledFunction();
           if (!NewCallee) {