Use base discriminator in sample pgo profile matching.

[danielcdh]

Summary

The discriminator has been encoded, and only the base discriminator should be used during profile matching.

[davidxl]

Is the modification of the existing tests good enough? Any standalone test needed?

[dblaikie]

This seems good to me - so long as the tests would fail if the implementation was reverted. (I haven't thought about it hard enough - but it's possible in general that a test could fail with a new implementation, be updated to be compatible with the new implementation - but also be compatible with the old implementation, thus not acting as a regression test against the new implementation/functionality)

[davidxl]

lgtm

lib/Transforms/IPO/SampleProfile.cpp

ErrorOr<uint64_t> SampleProfileLoader::getInstWeight(const Instruction &Inst) {
   // it means that the inlined callsite has no sample, thus the call
   // instruction should have 0 count.
   bool IsCall = isa<CallInst>(Inst) || isa<InvokeInst>(Inst);
   if (IsCall && findCalleeFunctionSamples(Inst))
     return 0;
 
   const DILocation *DIL = DLoc;
   uint32_t LineOffset = getOffset(DIL);
-  uint32_t Discriminator = DIL->getDiscriminator();
+  uint32_t Discriminator = DIL->getBaseDiscriminator();
   ErrorOr<uint64_t> R = IsCall
                             ? FS->findCallSamplesAt(LineOffset, Discriminator)
                             : FS->findSamplesAt(LineOffset, Discriminator);
   if (R) {
     bool FirstMark =
         CoverageTracker.markSamplesUsed(FS, LineOffset, Discriminator, R.get());
     if (FirstMark) {
       const Function *F = Inst.getParent()->getParent();
       LLVMContext &Ctx = F->getContext();
       emitOptimizationRemark(
           Ctx, DEBUG_TYPE, *F, DLoc,
           Twine("Applied ") + Twine(*R) +
               " samples from profile (offset: " + Twine(LineOffset) +
               ((Discriminator) ? Twine(".") + Twine(Discriminator) : "") + ")");
     }
-    DEBUG(dbgs() << "    " << DLoc.getLine() << "." << DIL->getDiscriminator()
-                 << ":" << Inst << " (line offset: " << LineOffset << "."
-                 << DIL->getDiscriminator() << " - weight: " << R.get()
+    DEBUG(dbgs() << "    " << DLoc.getLine() << "."
+                 << DIL->getBaseDiscriminator() << ":" << Inst
+                 << " (line offset: " << LineOffset << "."
+                 << DIL->getBaseDiscriminator() << " - weight: " << R.get()
                  << ")\n");
   }
   return R;
 }
 
 /// \brief Compute the weight of a basic block.
 ///
 /// The weight of basic block \p BB is the maximum weight of all the
SampleProfileLoader::findCalleeFunctionSamples(const Instruction &Inst) const {
   if (!DIL) {
     return nullptr;
   }
   const FunctionSamples *FS = findFunctionSamples(Inst);
   if (FS == nullptr)
     return nullptr;
 
   return FS->findFunctionSamplesAt(
-      LineLocation(getOffset(DIL), DIL->getDiscriminator()));
+      LineLocation(getOffset(DIL), DIL->getBaseDiscriminator()));
 }
 
 /// \brief Get the FunctionSamples for an instruction.
 ///
 /// The FunctionSamples of an instruction \p Inst is the inlined instance
 /// in which that instruction is coming from. We traverse the inline stack
 /// of that instruction, and match it with the tree nodes in the profile.
 ///
 /// \param Inst Instruction to query.
 ///
 /// \returns the FunctionSamples pointer to the inlined instance.
 const FunctionSamples *
 SampleProfileLoader::findFunctionSamples(const Instruction &Inst) const {
   SmallVector<LineLocation, 10> S;
   const DILocation *DIL = Inst.getDebugLoc();
   if (!DIL) {
     return Samples;
   }
   for (DIL = DIL->getInlinedAt(); DIL; DIL = DIL->getInlinedAt())
-    S.push_back(LineLocation(getOffset(DIL), DIL->getDiscriminator()));
+    S.push_back(LineLocation(getOffset(DIL), DIL->getBaseDiscriminator()));
   if (S.size() == 0)
     return Samples;
   const FunctionSamples *FS = Samples;
   for (int i = S.size() - 1; i >= 0 && FS != nullptr; i--) {
     FS = FS->findFunctionSamplesAt(S[i]);
   }
   return FS;
 }
if (BlockWeights[BB]) {
           continue;
         CallSite CS(&I);
         if (!CS.getCalledFunction()) {
           const DebugLoc &DLoc = I.getDebugLoc();
           if (!DLoc)
             continue;
           const DILocation *DIL = DLoc;
           uint32_t LineOffset = getOffset(DIL);
-          uint32_t Discriminator = DIL->getDiscriminator();
+          uint32_t Discriminator = DIL->getBaseDiscriminator();
 
           const FunctionSamples *FS = findFunctionSamples(I);
           if (!FS)
             continue;
           auto T = FS->findCallTargetMapAt(LineOffset, Discriminator);
           if (!T || T.get().size() == 0)
             continue;
           SmallVector<InstrProfValueData, 2> SortedCallTargets;

test/Transforms/SampleProfile/calls.ll

 !7 = distinct !DISubprogram(name: "main", line: 7, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 7, file: !1, scope: !5, type: !6, variables: !2)
 !8 = !{i32 2, !"Dwarf Version", i32 4}
 !9 = !{i32 1, !"Debug Info Version", i32 3}
 !10 = !{!"clang version 3.5 "}
 !11 = !DILocation(line: 4, scope: !4)
 !12 = !DILocation(line: 8, scope: !7)
 !13 = !DILocation(line: 9, scope: !7)
 !14 = !DILocation(line: 9, scope: !15)
-!15 = !DILexicalBlockFile(discriminator: 1, file: !1, scope: !7)
+!15 = !DILexicalBlockFile(discriminator: 2, file: !1, scope: !7)
 !16 = !DILocation(line: 10, scope: !17)
 !17 = distinct !DILexicalBlock(line: 10, column: 0, file: !1, scope: !7)
 !18 = !DILocation(line: 10, scope: !19)
-!19 = !DILexicalBlockFile(discriminator: 1, file: !1, scope: !17)
+!19 = !DILexicalBlockFile(discriminator: 2, file: !1, scope: !17)
 !20 = !DILocation(line: 10, scope: !21)
-!21 = !DILexicalBlockFile(discriminator: 2, file: !1, scope: !17)
+!21 = !DILexicalBlockFile(discriminator: 4, file: !1, scope: !17)
 !22 = !DILocation(line: 10, scope: !23)
-!23 = !DILexicalBlockFile(discriminator: 3, file: !1, scope: !17)
+!23 = !DILexicalBlockFile(discriminator: 6, file: !1, scope: !17)
 !24 = !DILocation(line: 11, scope: !7)
 !25 = !DILocation(line: 12, scope: !7)

test/Transforms/SampleProfile/cov-zero-samples.ll

 !8 = !{i32 2, !"Dwarf Version", i32 4}
 !9 = !{i32 2, !"Debug Info Version", i32 3}
 !10 = !{!"clang version 3.8.0 (trunk 253667) (llvm/trunk 253670)"}
 !11 = distinct !DISubprogram(name: "never_called", linkageName: "_Z12never_calledi", scope: !3, file: !3, line: 5, type: !12, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: false, unit: !2, variables: !4)
 !12 = !DISubroutineType(types: !13)
 !13 = !{!14, !14}
 !14 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 !15 = !DILocation(line: 5, column: 27, scope: !16)
-!16 = !DILexicalBlockFile(scope: !11, file: !3, discriminator: 3)
+!16 = !DILexicalBlockFile(scope: !11, file: !3, discriminator: 6)
 !17 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 7, type: !18, isLocal: false, isDefinition: true, scopeLine: 7, flags: DIFlagPrototyped, isOptimized: false, unit: !2, variables: !4)
 !18 = !DISubroutineType(types: !19)
 !19 = !{!14}
 !20 = !DILocalVariable(name: "sum", scope: !17, file: !3, line: 8, type: !14)
 !21 = !DIExpression()
 !22 = !DILocation(line: 8, column: 7, scope: !17)
 !23 = !DILocalVariable(name: "i", scope: !24, file: !3, line: 9, type: !7)
 !24 = distinct !DILexicalBlock(scope: !17, file: !3, line: 9, column: 3)
 !25 = !DILocation(line: 9, column: 18, scope: !24)
 !26 = !DILocation(line: 9, column: 8, scope: !24)
 !27 = !DILocation(line: 9, column: 25, scope: !28)
-!28 = !DILexicalBlockFile(scope: !29, file: !3, discriminator: 1)
+!28 = !DILexicalBlockFile(scope: !29, file: !3, discriminator: 2)
 !29 = distinct !DILexicalBlock(scope: !24, file: !3, line: 9, column: 3)
 !30 = !DILocation(line: 9, column: 29, scope: !28)
 !31 = !DILocation(line: 9, column: 27, scope: !28)
 !32 = !DILocation(line: 9, column: 3, scope: !28)
 !33 = !DILocation(line: 10, column: 9, scope: !34)
 !34 = distinct !DILexicalBlock(scope: !35, file: !3, line: 10, column: 9)
 !35 = distinct !DILexicalBlock(scope: !29, file: !3, line: 9, column: 37)
 !36 = !DILocation(line: 10, column: 13, scope: !34)
 !37 = !DILocation(line: 10, column: 11, scope: !34)
 !38 = !DILocation(line: 10, column: 9, scope: !35)
 !39 = !DILocation(line: 10, column: 36, scope: !40)
-!40 = !DILexicalBlockFile(scope: !34, file: !3, discriminator: 1)
+!40 = !DILexicalBlockFile(scope: !34, file: !3, discriminator: 2)
 !41 = !DILocation(line: 10, column: 23, scope: !40)
 !42 = !DILocation(line: 10, column: 20, scope: !40)
 !43 = !DILocation(line: 10, column: 16, scope: !40)
 !44 = !DILocation(line: 11, column: 12, scope: !35)
 !45 = !DILocation(line: 11, column: 14, scope: !35)
 !46 = !DILocation(line: 11, column: 9, scope: !35)
 !47 = !DILocation(line: 12, column: 3, scope: !35)
 !48 = !DILocation(line: 9, column: 33, scope: !49)
-!49 = !DILexicalBlockFile(scope: !29, file: !3, discriminator: 2)
+!49 = !DILexicalBlockFile(scope: !29, file: !3, discriminator: 4)
 !50 = !DILocation(line: 9, column: 3, scope: !49)
 !51 = !DILocation(line: 13, column: 25, scope: !17)
 !52 = !DILocation(line: 13, column: 3, scope: !17)
 !53 = !DILocation(line: 14, column: 3, scope: !17)
 

test/Transforms/SampleProfile/discriminator.ll

 !5 = !DIFile(filename: "discriminator.c", directory: ".")
 !6 = !DISubroutineType(types: !2)
 !7 = !{i32 2, !"Dwarf Version", i32 4}
 !8 = !{i32 1, !"Debug Info Version", i32 3}
 !9 = !{!"clang version 3.5 "}
 !10 = !DILocation(line: 2, scope: !4)
 !11 = !DILocation(line: 3, scope: !4)
 !12 = !DILocation(line: 3, scope: !13)
-!13 = !DILexicalBlockFile(discriminator: 1, file: !1, scope: !4)
+!13 = !DILexicalBlockFile(discriminator: 2, file: !1, scope: !4)
 !14 = !DILocation(line: 4, scope: !15)
 !15 = distinct !DILexicalBlock(line: 4, column: 0, file: !1, scope: !16)
 !16 = distinct !DILexicalBlock(line: 3, column: 0, file: !1, scope: !4)
 !17 = !DILocation(line: 4, scope: !18)
-!18 = !DILexicalBlockFile(discriminator: 1, file: !1, scope: !15)
+!18 = !DILexicalBlockFile(discriminator: 2, file: !1, scope: !15)
 !19 = !DILocation(line: 5, scope: !16)
 !20 = !DILocation(line: 6, scope: !16)
 !21 = !DILocation(line: 7, scope: !4)

test/Transforms/SampleProfile/inline-coverage.ll

 !22 = !DILocation(line: 4, column: 3, scope: !4)
 !23 = !DILocalVariable(name: "sum", scope: !9, file: !1, line: 8, type: !7)
 !24 = !DILocation(line: 8, column: 17, scope: !9)
 !25 = !DILocalVariable(name: "i", scope: !26, file: !1, line: 9, type: !12)
 !26 = distinct !DILexicalBlock(scope: !9, file: !1, line: 9, column: 3)
 !27 = !DILocation(line: 9, column: 12, scope: !26)
 !28 = !DILocation(line: 9, column: 8, scope: !26)
 !29 = !DILocation(line: 9, column: 19, scope: !30)
-!30 = !DILexicalBlockFile(scope: !31, file: !1, discriminator: 1)
+!30 = !DILexicalBlockFile(scope: !31, file: !1, discriminator: 2)
 !31 = distinct !DILexicalBlock(scope: !26, file: !1, line: 9, column: 3)
 !32 = !DILocation(line: 9, column: 21, scope: !30)
 !33 = !DILocation(line: 9, column: 3, scope: !30)
 !34 = !DILocation(line: 10, column: 16, scope: !31)
 !35 = !DILocation(line: 10, column: 12, scope: !31)
 !36 = !DILocation(line: 10, column: 9, scope: !31)
 !37 = !DILocation(line: 10, column: 5, scope: !31)
 !38 = !DILocation(line: 9, column: 39, scope: !31)
 !39 = !DILocation(line: 9, column: 3, scope: !31)
 !40 = !DILocation(line: 11, column: 10, scope: !9)
 !41 = !DILocation(line: 11, column: 14, scope: !9)
 !42 = !DILocation(line: 11, column: 3, scope: !9)

test/Transforms/SampleProfile/inline.ll

 !7 = distinct !DISubprogram(name: "main", line: 7, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 7, file: !1, scope: !5, type: !6, variables: !2)
 !8 = !{i32 2, !"Dwarf Version", i32 4}
 !9 = !{i32 1, !"Debug Info Version", i32 3}
 !10 = !{!"clang version 3.5 "}
 !11 = !DILocation(line: 4, scope: !4)
 !12 = !DILocation(line: 8, scope: !7)
 !13 = !DILocation(line: 9, scope: !7)
 !14 = !DILocation(line: 9, scope: !15)
-!15 = !DILexicalBlockFile(discriminator: 1, file: !1, scope: !7)
+!15 = !DILexicalBlockFile(discriminator: 2, file: !1, scope: !7)
 !16 = !DILocation(line: 10, scope: !17)
 !17 = distinct !DILexicalBlock(line: 10, column: 0, file: !1, scope: !7)
 !18 = !DILocation(line: 10, scope: !19)
-!19 = !DILexicalBlockFile(discriminator: 1, file: !1, scope: !17)
+!19 = !DILexicalBlockFile(discriminator: 2, file: !1, scope: !17)
 !20 = !DILocation(line: 10, scope: !21)
-!21 = !DILexicalBlockFile(discriminator: 2, file: !1, scope: !17)
+!21 = !DILexicalBlockFile(discriminator: 4, file: !1, scope: !17)
 !22 = !DILocation(line: 10, scope: !23)
-!23 = !DILexicalBlockFile(discriminator: 3, file: !1, scope: !17)
+!23 = !DILexicalBlockFile(discriminator: 6, file: !1, scope: !17)
 !24 = !DILocation(line: 11, scope: !7)
 !25 = !DILocation(line: 12, scope: !7)

test/Transforms/SampleProfile/propagate.ll

 !26 = !DILocation(line: 5, column: 14, scope: !24)
 !27 = !DILocation(line: 5, column: 5, scope: !24)
 !28 = !DILocalVariable(name: "i", scope: !29, file: !1, line: 7, type: !9)
 !29 = distinct !DILexicalBlock(scope: !30, file: !1, line: 7, column: 5)
 !30 = distinct !DILexicalBlock(scope: !19, file: !1, line: 6, column: 10)
 !31 = !DILocation(line: 7, column: 15, scope: !29)
 !32 = !DILocation(line: 7, column: 10, scope: !29)
 !33 = !DILocation(line: 7, column: 22, scope: !34)
-!34 = !DILexicalBlockFile(scope: !35, file: !1, discriminator: 1)
+!34 = !DILexicalBlockFile(scope: !35, file: !1, discriminator: 2)
 !35 = distinct !DILexicalBlock(scope: !29, file: !1, line: 7, column: 5)
 !36 = !DILocation(line: 7, column: 26, scope: !34)
 !37 = !DILocation(line: 7, column: 24, scope: !34)
 !38 = !DILocation(line: 7, column: 5, scope: !34)
 !39 = !DILocation(line: 8, column: 11, scope: !40)
 !40 = distinct !DILexicalBlock(scope: !41, file: !1, line: 8, column: 11)
 !41 = distinct !DILexicalBlock(scope: !35, file: !1, line: 7, column: 34)
 !42 = !DILocation(line: 8, column: 15, scope: !40)

 !57 = !DILocation(line: 13, column: 7, scope: !55)
 !58 = !DILocalVariable(name: "j", scope: !59, file: !1, line: 14, type: !61)
 !59 = distinct !DILexicalBlock(scope: !60, file: !1, line: 14, column: 9)
 !60 = distinct !DILexicalBlock(scope: !49, file: !1, line: 13, column: 14)
 !61 = !DIBasicType(name: "long long int", size: 64, align: 64, encoding: DW_ATE_signed)
 !62 = !DILocation(line: 14, column: 24, scope: !59)
 !63 = !DILocation(line: 14, column: 14, scope: !59)
 !64 = !DILocation(line: 14, column: 31, scope: !65)
-!65 = !DILexicalBlockFile(scope: !66, file: !1, discriminator: 1)
+!65 = !DILexicalBlockFile(scope: !66, file: !1, discriminator: 2)
 !66 = distinct !DILexicalBlock(scope: !59, file: !1, line: 14, column: 9)
 !67 = !DILocation(line: 14, column: 33, scope: !65)
 !68 = !DILocation(line: 14, column: 9, scope: !65)
 !69 = !DILocation(line: 15, column: 16, scope: !70)
 !70 = distinct !DILexicalBlock(scope: !66, file: !1, line: 14, column: 45)
 !71 = !DILocation(line: 15, column: 13, scope: !70)
 !72 = !DILocation(line: 16, column: 13, scope: !70)
 !73 = !DILocation(line: 17, column: 9, scope: !70)
 !74 = !DILocation(line: 14, column: 41, scope: !75)
-!75 = !DILexicalBlockFile(scope: !66, file: !1, discriminator: 2)
+!75 = !DILexicalBlockFile(scope: !66, file: !1, discriminator: 4)
 !76 = !DILocation(line: 14, column: 9, scope: !75)
 !77 = !DILocation(line: 19, column: 5, scope: !41)
 !78 = !DILocation(line: 7, column: 30, scope: !79)
-!79 = !DILexicalBlockFile(scope: !35, file: !1, discriminator: 2)
+!79 = !DILexicalBlockFile(scope: !35, file: !1, discriminator: 4)
 !80 = !DILocation(line: 7, column: 5, scope: !79)
 !81 = !DILocation(line: 21, column: 10, scope: !6)
 !82 = !DILocation(line: 21, column: 14, scope: !6)
 !83 = !DILocation(line: 21, column: 12, scope: !6)
 !84 = !DILocation(line: 21, column: 3, scope: !6)
 !85 = !DILocation(line: 22, column: 1, scope: !6)
 !86 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 24, type: !87, isLocal: false, isDefinition: true, scopeLine: 24, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
 !87 = !DISubroutineType(types: !88)
 !88 = !{!10}
 !89 = !DILocalVariable(name: "x", scope: !86, file: !1, line: 25, type: !10)
 !90 = !DILocation(line: 25, column: 7, scope: !86)
 !91 = !DILocalVariable(name: "y", scope: !86, file: !1, line: 26, type: !10)
 !92 = !DILocation(line: 26, column: 7, scope: !86)
 !93 = !DILocalVariable(name: "N", scope: !86, file: !1, line: 27, type: !9)
 !94 = !DILocation(line: 27, column: 8, scope: !86)
 !95 = !DILocation(line: 28, column: 38, scope: !86)
 !96 = !DILocation(line: 28, column: 41, scope: !86)
 !97 = !DILocation(line: 28, column: 44, scope: !86)
 !98 = !DILocation(line: 28, column: 51, scope: !86)
 !99 = !DILocation(line: 28, column: 54, scope: !86)
 !100 = !DILocation(line: 28, column: 57, scope: !86)
 !101 = !DILocation(line: 28, column: 47, scope: !86)
 !102 = !DILocation(line: 28, column: 3, scope: !103)
-!103 = !DILexicalBlockFile(scope: !86, file: !1, discriminator: 1)
+!103 = !DILexicalBlockFile(scope: !86, file: !1, discriminator: 2)
 !104 = !DILocation(line: 29, column: 3, scope: !86)