Only sets profile summary when it was not preset.

[danielcdh]

Summary

SampleProfileLoader pass may be invoked twice by LTO. The 2nd pass should not append more summary info as it is already preset by the 1st pass.

[davidxl]

lgtm

lib/Transforms/IPO/SampleProfile.cpp

for (const auto &I : Reader->getProfiles())
     TotalCollectedSamples += I.second.getTotalSamples();
 
   bool retval = false;
   for (auto &F : M)
     if (!F.isDeclaration()) {
       clearFunctionData();
       retval |= runOnFunction(F);
     }
+  if (M.getProfileSummary() == nullptr)
     M.setProfileSummary(Reader->getSummary().getMD(M.getContext()));
   return retval;
 }
 
 bool SampleProfileLoaderLegacyPass::runOnModule(Module &M) {
   // FIXME: pass in AssumptionCache correctly for the new pass manager.
   SampleLoader.setACT(&getAnalysis<AssumptionCacheTracker>());
   return SampleLoader.runOnModule(M);
 }

test/Transforms/SampleProfile/summary.ll

 ; Test that we annotate entire program's summary to IR.
 ; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/summary.prof -S | FileCheck %s
+; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/summary.prof -S | opt -sample-profile -sample-profile-file=%S/Inputs/summary.prof -S | FileCheck %s
 
 define i32 @bar() #0 !dbg !1 {
 entry:
   ret i32 1, !dbg !2
 }
 
 ; CHECK-DAG: {{![0-9]+}} = !{i32 1, !"ProfileSummary", {{![0-9]+}}}
 ; CHECK-DAG: {{![0-9]+}} = !{!"NumFunctions", i64 2}
 ; CHECK-DAG: {{![0-9]+}} = !{!"MaxFunctionCount", i64 3}
 
 !1 = distinct !DISubprogram(name: "bar")
 !2 = !DILocation(line: 2, scope: !2)