Set function entry count as 0 if sample profile is not found for the function.

[danielcdh]

Summary

This change makes the sample profile's behavior consistent with instr profile.

[dnovillo]

LGTM.

Thanks.

lib/Transforms/IPO/SampleProfile.cpp

for (auto &F : M)
     if (!F.isDeclaration()) {
       clearFunctionData();
       retval |= runOnFunction(F);
     }
   return retval;
 }
 
 bool SampleProfileLoader::runOnFunction(Function &F) {
+  F.setEntryCount(0);
   Samples = Reader->getSamplesFor(F);
   if (!Samples->empty())
     return emitAnnotations(F);
   return false;
 }

test/Transforms/SampleProfile/entry_counts.ll

 ; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/entry_counts.prof -S | FileCheck %s
 
 ; According to the profile, function empty() was called 13,293 times.
 ; CHECK: {{.*}} = !{!"function_entry_count", i64 13293}
 
 define void @empty() !dbg !4 {
 entry:
   ret void, !dbg !9
 }
 
+; This function does not have profile, check if function_entry_count is 0
+; CHECK: {{.*}} = !{!"function_entry_count", i64 0}
+define void @no_profile() {
+entry:
+  ret void
+}
+
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!6, !7}
 !llvm.ident = !{!8}
 
 !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.7.0 (trunk 237249) (llvm/trunk 237261)", isOptimized: false, runtimeVersion: 0, emissionKind: 2, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
 !1 = !DIFile(filename: "entry_counts.c", directory: ".")
 !2 = !{}
 !3 = !{!4}
 !4 = distinct !DISubprogram(name: "empty", scope: !1, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: false, variables: !2)
 !5 = !DISubroutineType(types: !2)
 !6 = !{i32 2, !"Dwarf Version", i32 4}
 !7 = !{i32 2, !"Debug Info Version", i32 3}
 !8 = !{!"clang version 3.7.0 (trunk 237249) (llvm/trunk 237261)"}
 !9 = !DILocation(line: 1, column: 15, scope: !4)