[LTO] Ignore unreachable virtual functions in WPD in hybrid LTO.

Differential Revision: https://reviews.llvm.org/D115492

Author: mingmingl-llvm

clang/test/CodeGen/thinlto-distributed-cfi-devirt.ll

@@ -36,7 +36,7 @@
 ; Round trip it through llvm-as
 ; RUN: llvm-dis %t.o.thinlto.bc -o - | llvm-as -o - | llvm-dis -o - | FileCheck %s --check-prefix=CHECK-DIS
 ; CHECK-DIS: ^0 = module: (path: "{{.*}}thinlto-distributed-cfi-devirt.ll.tmp.o", hash: ({{.*}}, {{.*}}, {{.*}}, {{.*}}, {{.*}}))
-; CHECK-DIS: ^1 = gv: (guid: 8346051122425466633, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 1, dsoLocal: 0, canAutoHide: 0), insts: 18, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 0, returnDoesNotAlias: 0, noInline: 0, alwaysInline: 0, noUnwind: 0, mayThrow: 0, hasUnknownCall: 1), typeIdInfo: (typeTests: (^2), typeCheckedLoadVCalls: (vFuncId: (^2, offset: 8), vFuncId: (^2, offset: 0))))))
+; CHECK-DIS: ^1 = gv: (guid: 8346051122425466633, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 1, dsoLocal: 0, canAutoHide: 0), insts: 18, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 0, returnDoesNotAlias: 0, noInline: 0, alwaysInline: 0, noUnwind: 0, mayThrow: 0, hasUnknownCall: 1, mustBeUnreachable: 0), typeIdInfo: (typeTests: (^2), typeCheckedLoadVCalls: (vFuncId: (^2, offset: 8), vFuncId: (^2, offset: 0))))))
 ; CHECK-DIS: ^2 = typeid: (name: "_ZTS1A", summary: (typeTestRes: (kind: allOnes, sizeM1BitWidth: 7), wpdResolutions: ((offset: 0, wpdRes: (kind: branchFunnel)), (offset: 8, wpdRes: (kind: singleImpl, singleImplName: "_ZN1A1nEi"))))) ; guid = 7004155349499253778
 
 ; RUN: %clang_cc1 -triple x86_64-grtev4-linux-gnu \

clang/test/CodeGen/thinlto-distributed-cfi.ll

@@ -24,7 +24,7 @@
 ; Round trip it through llvm-as
 ; RUN: llvm-dis %t.o.thinlto.bc -o - | llvm-as -o - | llvm-dis -o - | FileCheck %s --check-prefix=CHECK-DIS
 ; CHECK-DIS: ^0 = module: (path: "{{.*}}thinlto-distributed-cfi.ll.tmp.o", hash: ({{.*}}, {{.*}}, {{.*}}, {{.*}}, {{.*}}))
-; CHECK-DIS: ^1 = gv: (guid: 8346051122425466633, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 1, dsoLocal: 0, canAutoHide: 0), insts: 7, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 1, returnDoesNotAlias: 0, noInline: 0, alwaysInline: 0, noUnwind: 1, mayThrow: 0, hasUnknownCall: 0), typeIdInfo: (typeTests: (^2)))))
+; CHECK-DIS: ^1 = gv: (guid: 8346051122425466633, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 1, dsoLocal: 0, canAutoHide: 0), insts: 7, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 1, returnDoesNotAlias: 0, noInline: 0, alwaysInline: 0, noUnwind: 1, mayThrow: 0, hasUnknownCall: 0, mustBeUnreachable: 0), typeIdInfo: (typeTests: (^2)))))
 ; CHECK-DIS: ^2 = typeid: (name: "_ZTS1A", summary: (typeTestRes: (kind: single, sizeM1BitWidth: 0))) ; guid = 7004155349499253778
 
 ; RUN: %clang_cc1 -triple x86_64-grtev4-linux-gnu \

clang/test/CodeGen/thinlto-funcattr-prop.ll

@@ -17,7 +17,7 @@
 ;; Summary for call_extern. Note that llvm-lto2 writes out the index before propagation occurs so call_extern doesn't have its flags updated.
 ; CHECK-INDEX: ^2 = gv: (guid: 13959900437860518209, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 1, dsoLocal: 1, canAutoHide: 0), insts: 2, calls: ((callee: ^3)))))
 ;; Summary for extern
-; CHECK-INDEX: ^3 = gv: (guid: 14959766916849974397, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 1, dsoLocal: 0, canAutoHide: 0), insts: 1, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 1, returnDoesNotAlias: 0, noInline: 0, alwaysInline: 0, noUnwind: 1, mayThrow: 0, hasUnknownCall: 0))))
+; CHECK-INDEX: ^3 = gv: (guid: 14959766916849974397, summaries: (function: (module: ^1, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 1, dsoLocal: 0, canAutoHide: 0), insts: 1, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 1, returnDoesNotAlias: 0, noInline: 0, alwaysInline: 0, noUnwind: 1, mayThrow: 0, hasUnknownCall: 0, mustBeUnreachable: 0))))
 
 ;--- a.ll
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"

llvm/include/llvm/AsmParser/LLToken.h

@@ -407,6 +407,7 @@ enum Kind {
   kw_noUnwind,
   kw_mayThrow,
   kw_hasUnknownCall,
+  kw_mustBeUnreachable,
   kw_calls,
   kw_callee,
   kw_params,

llvm/include/llvm/IR/ModuleSummaryIndex.h

@@ -581,6 +581,13 @@ class FunctionSummary : public GlobalValueSummary {
     // If there are calls to unknown targets (e.g. indirect)
     unsigned HasUnknownCall : 1;
 
+    // Indicate if a function must be an unreachable function.
+    //
+    // This bit is sufficient but not necessary;
+    // if this bit is on, the function must be regarded as unreachable;
+    // if this bit is off, the function might be reachable or unreachable.
+    unsigned MustBeUnreachable : 1;
+
     FFlags &operator&=(const FFlags &RHS) {
       this->ReadNone &= RHS.ReadNone;
       this->ReadOnly &= RHS.ReadOnly;
@@ -591,13 +598,15 @@ class FunctionSummary : public GlobalValueSummary {
       this->NoUnwind &= RHS.NoUnwind;
       this->MayThrow &= RHS.MayThrow;
       this->HasUnknownCall &= RHS.HasUnknownCall;
+      this->MustBeUnreachable &= RHS.MustBeUnreachable;
       return *this;
     }
 
     bool anyFlagSet() {
       return this->ReadNone | this->ReadOnly | this->NoRecurse |
              this->ReturnDoesNotAlias | this->NoInline | this->AlwaysInline |
-             this->NoUnwind | this->MayThrow | this->HasUnknownCall;
+             this->NoUnwind | this->MayThrow | this->HasUnknownCall |
+             this->MustBeUnreachable;
     }
 
     operator std::string() {
@@ -613,6 +622,7 @@ class FunctionSummary : public GlobalValueSummary {
       OS << ", noUnwind: " << this->NoUnwind;
       OS << ", mayThrow: " << this->MayThrow;
       OS << ", hasUnknownCall: " << this->HasUnknownCall;
+      OS << ", mustBeUnreachable: " << this->MustBeUnreachable;
       OS << ")";
       return OS.str();
     }

llvm/lib/Analysis/ModuleSummaryAnalysis.cpp

@@ -234,6 +234,26 @@ static bool isNonVolatileStore(const Instruction *I) {
   return false;
 }
 
+// Returns true if `F` must be an unreachable function.
+//
+// Note if this helper function returns true, `F` is guaranteed
+// to be unreachable; if it returns false, `F` might still
+// be unreachable but not covered by this helper function.
+static bool mustBeUnreachableFunction(const Function &F) {
+  if (!F.empty()) {
+    const BasicBlock &entryBlock = F.getEntryBlock();
+    // A function must be unreachable if its entry block
+    // ends with an 'unreachable'.
+    if (!entryBlock.empty()) {
+      const Instruction *inst = &(*entryBlock.rbegin());
+      if (inst->getOpcode() == Instruction::Unreachable) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 static void computeFunctionSummary(
     ModuleSummaryIndex &Index, const Module &M, const Function &F,
     BlockFrequencyInfo *BFI, ProfileSummaryInfo *PSI, DominatorTree &DT,
@@ -488,7 +508,8 @@ static void computeFunctionSummary(
       // Don't try to import functions with noinline attribute.
       F.getAttributes().hasFnAttr(Attribute::NoInline),
       F.hasFnAttribute(Attribute::AlwaysInline),
-      F.hasFnAttribute(Attribute::NoUnwind), MayThrow, HasUnknownCall};
+      F.hasFnAttribute(Attribute::NoUnwind), MayThrow, HasUnknownCall,
+      mustBeUnreachableFunction(F)};
   std::vector<FunctionSummary::ParamAccess> ParamAccesses;
   if (auto *SSI = GetSSICallback(F))
     ParamAccesses = SSI->getParamAccesses(Index);
@@ -737,7 +758,8 @@ ModuleSummaryIndex llvm::buildModuleSummaryIndex(
                         F->hasFnAttribute(Attribute::AlwaysInline),
                         F->hasFnAttribute(Attribute::NoUnwind),
                         /* MayThrow */ true,
-                        /* HasUnknownCall */ true},
+                        /* HasUnknownCall */ true,
+                        /* MustBeUnreachable */ false},
                     /*EntryCount=*/0, ArrayRef<ValueInfo>{},
                     ArrayRef<FunctionSummary::EdgeTy>{},
                     ArrayRef<GlobalValue::GUID>{},

llvm/lib/AsmParser/LLLexer.cpp

@@ -773,6 +773,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(noUnwind);
   KEYWORD(mayThrow);
   KEYWORD(hasUnknownCall);
+  KEYWORD(mustBeUnreachable);
   KEYWORD(calls);
   KEYWORD(callee);
   KEYWORD(params);

llvm/lib/AsmParser/LLParser.cpp

@@ -8534,6 +8534,7 @@ bool LLParser::parseFlag(unsigned &Val) {
 ///        [',' 'noUnwind' ':' Flag]? ')'
 ///        [',' 'mayThrow' ':' Flag]? ')'
 ///        [',' 'hasUnknownCall' ':' Flag]? ')'
+///        [',' 'mustBeUnreachable' ':' Flag]? ')'
 
 bool LLParser::parseOptionalFFlags(FunctionSummary::FFlags &FFlags) {
   assert(Lex.getKind() == lltok::kw_funcFlags);
@@ -8600,6 +8601,12 @@ bool LLParser::parseOptionalFFlags(FunctionSummary::FFlags &FFlags) {
         return true;
       FFlags.HasUnknownCall = Val;
       break;
+    case lltok::kw_mustBeUnreachable:
+      Lex.Lex();
+      if (parseToken(lltok::colon, "expected ':'") || parseFlag(Val))
+        return true;
+      FFlags.MustBeUnreachable = Val;
+      break;
     default:
       return error(Lex.getLoc(), "expected function flag type");
     }

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -932,6 +932,7 @@ static FunctionSummary::FFlags getDecodedFFlags(uint64_t RawFlags) {
   Flags.NoUnwind = (RawFlags >> 6) & 0x1;
   Flags.MayThrow = (RawFlags >> 7) & 0x1;
   Flags.HasUnknownCall = (RawFlags >> 8) & 0x1;
+  Flags.MustBeUnreachable = (RawFlags >> 9) & 0x1;
   return Flags;
 }
 

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -1066,6 +1066,7 @@ static uint64_t getEncodedFFlags(FunctionSummary::FFlags Flags) {
   RawFlags |= (Flags.NoUnwind << 6);
   RawFlags |= (Flags.MayThrow << 7);
   RawFlags |= (Flags.HasUnknownCall << 8);
+  RawFlags |= (Flags.MustBeUnreachable << 9);
   return RawFlags;
 }