Fix PR28219: Use profile summary from reader and not compute it

[eraman]

Summary

This fixes the root cause of PR28219 - profile summar metadata mismatch in LTO mode. This probably needs an LTO test too - what would be the right place to have it?

[jakev]

So even after applying this patch, IRMover is still emitting an error. I
believe the root cause of this is that we do a pointer based comparison of
the metadata values. This has worked until now when we have constant values
because we unique them in the IR, but doesn't for the ProfileSummary value
which references another metadata entry. If you could, please take a look
and let me know if I'm seeing things correctly.

[jakev]

Scratch that, please ignore my previous comment. My own naivety and an IR file with stale ProfileSummary info in the build was causing the error. This patch does in fact fix the problem when not using IR/bitcode files in that way.

[davidxl]

lgtm

lib/Transforms/Instrumentation/PGOInstrumentation.cpp

static bool annotateAllFunctions(
   if (!PGOReader->isIRLevelProfile()) {
     Ctx.diagnose(DiagnosticInfoPGOProfile(
         ProfileFileName.data(), "Not an IR level instrumentation profile"));
     return false;
   }
 
   std::vector<Function *> HotFunctions;
   std::vector<Function *> ColdFunctions;
-  InstrProfSummaryBuilder Builder(ProfileSummaryBuilder::DefaultCutoffs);
   for (auto &F : M) {
     if (F.isDeclaration())
       continue;
     auto *BPI = LookupBPI(F);
     auto *BFI = LookupBFI(F);
     PGOUseFunc Func(F, &M, BPI, BFI);
     if (!Func.readCounters(PGOReader.get()))
       continue;
     Func.populateCounters();
     Func.setBranchWeights();
     Func.annotateIndirectCallSites();
-    if (!Func.getProfileRecord().Counts.empty())
-      Builder.addRecord(Func.getProfileRecord());
     PGOUseFunc::FuncFreqAttr FreqAttr = Func.getFuncFreqAttr();
     if (FreqAttr == PGOUseFunc::FFA_Cold)
       ColdFunctions.push_back(&F);
     else if (FreqAttr == PGOUseFunc::FFA_Hot)
       HotFunctions.push_back(&F);
   }
-  M.setProfileSummary(Builder.getSummary()->getMD(M.getContext()));
+  M.setProfileSummary(PGOReader->getSummary().getMD(M.getContext()));
   // Set function hotness attribute from the profile.
   // We have to apply these attributes at the end because their presence
   // can affect the BranchProbabilityInfo of any callers, resulting in an
   // inconsistent MST between prof-gen and prof-use.
   for (auto &F : HotFunctions) {
     F->addFnAttr(llvm::Attribute::InlineHint);
     DEBUG(dbgs() << "Set inline attribute to function: " << F->getName()
                  << "\n");

test/Transforms/PGOProfile/Inputs/PR28219.proftext

+# :ir is the flag to indicate this is IR level profile.
+:ir
+@bar
+256
+1
+2
+@foo
+512
+1
+3

test/Transforms/PGOProfile/PR28219.ll

+; Test that we annotate entire program's summary and not just this module's
+; RUN: llvm-profdata merge %S/Inputs/PR28219.proftext -o %t.profdata
+; RUN: opt < %s -pgo-instr-use -pgo-test-profile-file=%t.profdata -S | FileCheck %s
+
+define i32 @bar() {
+entry:
+  ret i32 1
+}
+; CHECK-DAG: {{![0-9]+}} = !{i32 1, !"ProfileSummary", {{![0-9]+}}}
+; CHECK-DAG: {{![0-9]+}} = !{!"NumFunctions", i64 2}
+; CHECK-DAG: {{![0-9]+}} = !{!"MaxFunctionCount", i64 3}
+