llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: Timm Baeder (tbaederr) <details> <summary>Changes</summary> Both `APInt` and `APFloat` will heap-allocate memory themselves using the system allocator when the size of their data exceeds 64 bits. This is why clang has `APNumericStorage`, which allocates its memory using an allocator (via `ASTContext`) instead. Calling `getValue()` on an ast node like that will then create a new `APInt`/`APFloat` , which will copy the data (in the `APFloat` case, we even copy it twice). That's sad but whatever. In the bytecode interpreter, we have a similar problem. Large integers and floating-point values are placement-new allocated into the `InterpStack` (or into the bytecode, which is a `vector<std::byte>`). When we then later interrupt interpretation, we don't run the destructor for all items on the stack, which means we leak the memory the `APInt`/`APFloat` (which backs the `IntegralAP`/`Floating` the interpreter uses). Fix this by using an approach similar to the one used in the AST. Add an allocator to `InterpState`, which is used for temporaries and local values. Those values will be freed at the end of interpretation. For global variables, we need to promote the values to global lifetime, which we do via `InitGlobal` and `FinishInitGlobal` ops. Interestingly, this results in a slight _improvement_ in compile times: https://llvm-compile-time-tracker.com/compare.php?from=6bfcdda9b1ddf0900f82f7e30cb5e3253a791d50&to=88d1d899127b408f0fb0f385c2c58e6283195049&stat=instructions:u (but don't ask my why). --- Patch is 83.35 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/144246.diff 17 Files Affected: - (modified) clang/lib/AST/ByteCode/Compiler.cpp (+63-49) - (modified) clang/lib/AST/ByteCode/Compiler.h (+1) - (modified) clang/lib/AST/ByteCode/Descriptor.cpp (+1-1) - (modified) clang/lib/AST/ByteCode/Disasm.cpp (+41-19) - (modified) clang/lib/AST/ByteCode/Floating.h (+170-83) - (modified) clang/lib/AST/ByteCode/Integral.h (+3) - (modified) clang/lib/AST/ByteCode/IntegralAP.h (+140-91) - (modified) clang/lib/AST/ByteCode/Interp.cpp (+102-4) - (modified) clang/lib/AST/ByteCode/Interp.h (+273-64) - (modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+44-12) - (modified) clang/lib/AST/ByteCode/InterpBuiltinBitCast.cpp (+3-1) - (modified) clang/lib/AST/ByteCode/InterpState.h (+31) - (modified) clang/lib/AST/ByteCode/Opcodes.td (+10-4) - (modified) clang/lib/AST/ByteCode/PrimType.h (+17) - (modified) clang/lib/AST/ByteCode/Program.h (+23-1) - (modified) clang/test/AST/ByteCode/builtin-bit-cast-long-double.cpp (+5-5) - (modified) clang/test/AST/ByteCode/builtin-functions.cpp (+5-7) ``````````diff diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp index bf38b2e5d537d..136bb46d2a516 100644 --- a/clang/lib/AST/ByteCode/Compiler.cpp +++ b/clang/lib/AST/ByteCode/Compiler.cpp @@ -748,7 +748,8 @@ bool Compiler<Emitter>::VisitFloatingLiteral(const FloatingLiteral *E) { if (DiscardResult) return true; - return this->emitConstFloat(E->getValue(), E); + APFloat F = E->getValue(); + return this->emitFloat(F, E); } template <class Emitter> @@ -4185,8 +4186,10 @@ bool Compiler<Emitter>::visitZeroInitializer(PrimType T, QualType QT, nullptr, E); case PT_MemberPtr: return this->emitNullMemberPtr(0, nullptr, E); - case PT_Float: - return this->emitConstFloat(APFloat::getZero(Ctx.getFloatSemantics(QT)), E); + case PT_Float: { + APFloat F = APFloat::getZero(Ctx.getFloatSemantics(QT)); + return this->emitFloat(F, E); + } case PT_FixedPoint: { auto Sem = Ctx.getASTContext().getFixedPointSemantics(E->getType()); return this->emitConstFixedPoint(FixedPoint::zero(Sem), E); @@ -4674,10 +4677,7 @@ VarCreationState Compiler<Emitter>::visitVarDecl(const VarDecl *VD, if (!visitInitializer(Init)) return false; - if (!this->emitFinishInit(Init)) - return false; - - return this->emitPopPtr(Init); + return this->emitFinishInitGlobal(Init); }; DeclScope<Emitter> LocalScope(this, VD); @@ -4698,51 +4698,45 @@ VarCreationState Compiler<Emitter>::visitVarDecl(const VarDecl *VD, return false; return !Init || (checkDecl() && initGlobal(*GlobalIndex)); - } else { - InitLinkScope<Emitter> ILS(this, InitLink::Decl(VD)); - - if (VarT) { - unsigned Offset = this->allocateLocalPrimitive( - VD, *VarT, VD->getType().isConstQualified(), nullptr, - ScopeKind::Block, IsConstexprUnknown); - if (Init) { - // If this is a toplevel declaration, create a scope for the - // initializer. - if (Toplevel) { - LocalScope<Emitter> Scope(this); - if (!this->visit(Init)) - return false; - return this->emitSetLocal(*VarT, Offset, VD) && Scope.destroyLocals(); - } else { - if (!this->visit(Init)) - return false; - return this->emitSetLocal(*VarT, Offset, VD); - } - } - } else { - if (std::optional<unsigned> Offset = - this->allocateLocal(VD, VD->getType(), nullptr, ScopeKind::Block, - IsConstexprUnknown)) { - if (!Init) - return true; + } + // Local variables. + InitLinkScope<Emitter> ILS(this, InitLink::Decl(VD)); - if (!this->emitGetPtrLocal(*Offset, Init)) + if (VarT) { + unsigned Offset = this->allocateLocalPrimitive( + VD, *VarT, VD->getType().isConstQualified(), nullptr, ScopeKind::Block, + IsConstexprUnknown); + if (Init) { + // If this is a toplevel declaration, create a scope for the + // initializer. + if (Toplevel) { + LocalScope<Emitter> Scope(this); + if (!this->visit(Init)) return false; - - if (!visitInitializer(Init)) + return this->emitSetLocal(*VarT, Offset, VD) && Scope.destroyLocals(); + } else { + if (!this->visit(Init)) return false; + return this->emitSetLocal(*VarT, Offset, VD); + } + } + } else { + if (std::optional<unsigned> Offset = this->allocateLocal( + VD, VD->getType(), nullptr, ScopeKind::Block, IsConstexprUnknown)) { + if (!Init) + return true; - if (!this->emitFinishInit(Init)) - return false; + if (!this->emitGetPtrLocal(*Offset, Init)) + return false; - return this->emitPopPtr(Init); - } - return false; + if (!visitInitializer(Init)) + return false; + + return this->emitFinishInitPop(Init); } - return true; + return false; } - - return false; + return true; } template <class Emitter> @@ -4751,8 +4745,10 @@ bool Compiler<Emitter>::visitAPValue(const APValue &Val, PrimType ValType, assert(!DiscardResult); if (Val.isInt()) return this->emitConst(Val.getInt(), ValType, E); - else if (Val.isFloat()) - return this->emitConstFloat(Val.getFloat(), E); + else if (Val.isFloat()) { + APFloat F = Val.getFloat(); + return this->emitFloat(F, E); + } if (Val.isLValue()) { if (Val.isNullPointer()) @@ -6133,8 +6129,10 @@ bool Compiler<Emitter>::VisitUnaryOperator(const UnaryOperator *E) { const auto &TargetSemantics = Ctx.getFloatSemantics(E->getType()); if (!this->emitLoadFloat(E)) return false; - if (!this->emitConstFloat(llvm::APFloat(TargetSemantics, 1), E)) + APFloat F(TargetSemantics, 1); + if (!this->emitFloat(F, E)) return false; + if (!this->emitAddf(getFPOptions(E), E)) return false; if (!this->emitStoreFloat(E)) @@ -6176,8 +6174,10 @@ bool Compiler<Emitter>::VisitUnaryOperator(const UnaryOperator *E) { const auto &TargetSemantics = Ctx.getFloatSemantics(E->getType()); if (!this->emitLoadFloat(E)) return false; - if (!this->emitConstFloat(llvm::APFloat(TargetSemantics, 1), E)) + APFloat F(TargetSemantics, 1); + if (!this->emitFloat(F, E)) return false; + if (!this->emitSubf(getFPOptions(E), E)) return false; if (!this->emitStoreFloat(E)) @@ -6957,6 +6957,20 @@ bool Compiler<Emitter>::emitDummyPtr(const DeclTy &D, const Expr *E) { return true; } +template <class Emitter> +bool Compiler<Emitter>::emitFloat(const APFloat &F, const Expr *E) { + assert(!DiscardResult && "Should've been checked before"); + + if (Floating::singleWord(F.getSemantics())) + return this->emitConstFloat(Floating(F), E); + + APInt I = F.bitcastToAPInt(); + return this->emitConstFloat( + Floating(const_cast<uint64_t *>(I.getRawData()), + llvm::APFloatBase::SemanticsToEnum(F.getSemantics())), + E); +} + // This function is constexpr if and only if To, From, and the types of // all subobjects of To and From are types T such that... // (3.1) - is_union_v<T> is false; diff --git a/clang/lib/AST/ByteCode/Compiler.h b/clang/lib/AST/ByteCode/Compiler.h index ac3ad84766dc6..a1d068cc7e0ae 100644 --- a/clang/lib/AST/ByteCode/Compiler.h +++ b/clang/lib/AST/ByteCode/Compiler.h @@ -391,6 +391,7 @@ class Compiler : public ConstStmtVisitor<Compiler<Emitter>, bool>, bool emitRecordDestruction(const Record *R, SourceInfo Loc); bool emitDestruction(const Descriptor *Desc, SourceInfo Loc); bool emitDummyPtr(const DeclTy &D, const Expr *E); + bool emitFloat(const APFloat &F, const Expr *E); unsigned collectBaseOffset(const QualType BaseType, const QualType DerivedType); bool emitLambdaStaticInvokerBody(const CXXMethodDecl *MD); diff --git a/clang/lib/AST/ByteCode/Descriptor.cpp b/clang/lib/AST/ByteCode/Descriptor.cpp index 5531295dfa2f8..46e4d0d940b3e 100644 --- a/clang/lib/AST/ByteCode/Descriptor.cpp +++ b/clang/lib/AST/ByteCode/Descriptor.cpp @@ -368,7 +368,7 @@ Descriptor::Descriptor(const DeclTy &D, PrimType Type, MetadataSize MD, bool IsTemporary, bool IsConst, UnknownSize) : Source(D), ElemSize(primSize(Type)), Size(UnknownSizeMark), MDSize(MD.value_or(0)), - AllocSize(MDSize + sizeof(InitMapPtr) + alignof(void *)), + AllocSize(MDSize + sizeof(InitMapPtr) + alignof(void *)), PrimT(Type), IsConst(IsConst), IsMutable(false), IsTemporary(IsTemporary), IsArray(true), CtorFn(getCtorArrayPrim(Type)), DtorFn(getDtorArrayPrim(Type)), MoveFn(getMoveArrayPrim(Type)) { diff --git a/clang/lib/AST/ByteCode/Disasm.cpp b/clang/lib/AST/ByteCode/Disasm.cpp index 846dc2fe92a70..7c6b78386b14f 100644 --- a/clang/lib/AST/ByteCode/Disasm.cpp +++ b/clang/lib/AST/ByteCode/Disasm.cpp @@ -50,34 +50,56 @@ inline static std::string printArg(Program &P, CodePtr &OpPC) { } template <> inline std::string printArg<Floating>(Program &P, CodePtr &OpPC) { - auto F = Floating::deserialize(*OpPC); - OpPC += align(F.bytesToSerialize()); + auto Sem = Floating::deserializeSemantics(*OpPC); - std::string Result; - llvm::raw_string_ostream SS(Result); - SS << F; - return Result; + unsigned BitWidth = llvm::APFloatBase::semanticsSizeInBits( + llvm::APFloatBase::EnumToSemantics(Sem)); + auto Memory = + std::make_unique<uint64_t[]>(llvm::APInt::getNumWords(BitWidth)); + Floating Result(Memory.get(), Sem); + Floating::deserialize(*OpPC, &Result); + + OpPC += align(Result.bytesToSerialize()); + + std::string S; + llvm::raw_string_ostream SS(S); + SS << Result; + return S; } template <> inline std::string printArg<IntegralAP<false>>(Program &P, CodePtr &OpPC) { - auto F = IntegralAP<false>::deserialize(*OpPC); - OpPC += align(F.bytesToSerialize()); - - std::string Result; - llvm::raw_string_ostream SS(Result); - SS << F; - return Result; + using T = IntegralAP<false>; + unsigned BitWidth = T::deserializeSize(*OpPC); + auto Memory = + std::make_unique<uint64_t[]>(llvm::APInt::getNumWords(BitWidth)); + + T Result(Memory.get(), BitWidth); + T::deserialize(*OpPC, &Result); + + OpPC += Result.bytesToSerialize(); + std::string Str; + llvm::raw_string_ostream SS(Str); + SS << Result; + return Str; } + template <> inline std::string printArg<IntegralAP<true>>(Program &P, CodePtr &OpPC) { - auto F = IntegralAP<true>::deserialize(*OpPC); - OpPC += align(F.bytesToSerialize()); + using T = IntegralAP<true>; + unsigned BitWidth = T::deserializeSize(*OpPC); + auto Memory = + std::make_unique<uint64_t[]>(llvm::APInt::getNumWords(BitWidth)); - std::string Result; - llvm::raw_string_ostream SS(Result); - SS << F; - return Result; + T Result(Memory.get(), BitWidth); + T::deserialize(*OpPC, &Result); + + std::string Str; + llvm::raw_string_ostream SS(Str); + SS << Result; + + OpPC += Result.bytesToSerialize(); + return Str; } template <> inline std::string printArg<FixedPoint>(Program &P, CodePtr &OpPC) { diff --git a/clang/lib/AST/ByteCode/Floating.h b/clang/lib/AST/ByteCode/Floating.h index 3750568fc23c7..f67c898f48eb1 100644 --- a/clang/lib/AST/ByteCode/Floating.h +++ b/clang/lib/AST/ByteCode/Floating.h @@ -17,63 +17,80 @@ #include "clang/AST/APValue.h" #include "llvm/ADT/APFloat.h" +// XXX This is just a debugging help. Setting this to 1 will heap-allocate ALL +// floating values. +#define ALLOCATE_ALL 0 + namespace clang { namespace interp { using APFloat = llvm::APFloat; using APSInt = llvm::APSInt; +using APInt = llvm::APInt; +/// If a Floating is constructed from Memory, it DOES NOT OWN THAT MEMORY. +/// It will NOT copy the memory (unless, of course, copy() is called) an it +/// won't alllocate anything. The allocation should happen via InterpState or +/// Program. class Floating final { private: - // The underlying value storage. - APFloat F; + union { + uint64_t Val = 0; + uint64_t *Memory; + }; + llvm::APFloatBase::Semantics Semantics = + llvm::APFloatBase::Semantics::S_IEEEhalf; + + APFloat getValue() const { + unsigned BitWidth = bitWidth(); + if (singleWord()) + return APFloat(getSemantics(), APInt(BitWidth, Val)); + unsigned NumWords = numWords(); + return APFloat(getSemantics(), APInt(BitWidth, NumWords, Memory)); + } public: - /// Zero-initializes a Floating. - Floating() : F(0.0f) {} - Floating(const APFloat &F) : F(F) {} + Floating() = default; + Floating(llvm::APFloatBase::Semantics Semantics) + : Val(0), Semantics(Semantics) {} + Floating(const APFloat &F) { - // Static constructors for special floating point values. - static Floating getInf(const llvm::fltSemantics &Sem) { - return Floating(APFloat::getInf(Sem)); + Semantics = llvm::APFloatBase::SemanticsToEnum(F.getSemantics()); + this->copy(F); } - const APFloat &getAPFloat() const { return F; } + Floating(uint64_t *Memory, llvm::APFloatBase::Semantics Semantics) + : Memory(Memory), Semantics(Semantics) {} + + APFloat getAPFloat() const { return getValue(); } - bool operator<(Floating RHS) const { return F < RHS.F; } - bool operator>(Floating RHS) const { return F > RHS.F; } - bool operator<=(Floating RHS) const { return F <= RHS.F; } - bool operator>=(Floating RHS) const { return F >= RHS.F; } - bool operator==(Floating RHS) const { return F == RHS.F; } - bool operator!=(Floating RHS) const { return F != RHS.F; } - Floating operator-() const { return Floating(-F); } + bool operator<(Floating RHS) const { return getValue() < RHS.getValue(); } + bool operator>(Floating RHS) const { return getValue() > RHS.getValue(); } + bool operator<=(Floating RHS) const { return getValue() <= RHS.getValue(); } + bool operator>=(Floating RHS) const { return getValue() >= RHS.getValue(); } APFloat::opStatus convertToInteger(APSInt &Result) const { bool IsExact; - return F.convertToInteger(Result, llvm::APFloat::rmTowardZero, &IsExact); + return getValue().convertToInteger(Result, llvm::APFloat::rmTowardZero, + &IsExact); } - Floating toSemantics(const llvm::fltSemantics *Sem, - llvm::RoundingMode RM) const { - APFloat Copy = F; + void toSemantics(const llvm::fltSemantics *Sem, llvm::RoundingMode RM, + Floating *Result) const { + APFloat Copy = getValue(); bool LosesInfo; Copy.convert(*Sem, RM, &LosesInfo); (void)LosesInfo; - return Floating(Copy); - } - - /// Convert this Floating to one with the same semantics as \Other. - Floating toSemantics(const Floating &Other, llvm::RoundingMode RM) const { - return toSemantics(&Other.F.getSemantics(), RM); + Result->copy(Copy); } APSInt toAPSInt(unsigned NumBits = 0) const { - return APSInt(F.bitcastToAPInt()); + return APSInt(getValue().bitcastToAPInt()); } - APValue toAPValue(const ASTContext &) const { return APValue(F); } + APValue toAPValue(const ASTContext &) const { return APValue(getValue()); } void print(llvm::raw_ostream &OS) const { // Can't use APFloat::print() since it appends a newline. SmallVector<char, 16> Buffer; - F.toString(Buffer); + getValue().toString(Buffer); OS << Buffer; } std::string toDiagnosticString(const ASTContext &Ctx) const { @@ -83,25 +100,62 @@ class Floating final { return NameStr; } - unsigned bitWidth() const { return F.semanticsSizeInBits(F.getSemantics()); } + unsigned bitWidth() const { + return llvm::APFloatBase::semanticsSizeInBits(getSemantics()); + } + unsigned numWords() const { return llvm::APInt::getNumWords(bitWidth()); } + bool singleWord() const { +#if ALLOCATE_ALL + return false; +#endif + return numWords() == 1; + } + static bool singleWord(const llvm::fltSemantics &Sem) { +#if ALLOCATE_ALL + return false; +#endif + return APInt::getNumWords(llvm::APFloatBase::getSizeInBits(Sem)) == 1; + } + const llvm::fltSemantics &getSemantics() const { + return llvm::APFloatBase::EnumToSemantics(Semantics); + } + + void copy(const APFloat &F) { + if (singleWord()) { + Val = F.bitcastToAPInt().getZExtValue(); + } else { + assert(Memory); + std::memcpy(Memory, F.bitcastToAPInt().getRawData(), + numWords() * sizeof(uint64_t)); + } + } + + void take(uint64_t *NewMemory) { + if (singleWord()) + return; + + if (Memory) + std::memcpy(NewMemory, Memory, numWords() * sizeof(uint64_t)); + Memory = NewMemory; + } bool isSigned() const { return true; } - bool isNegative() const { return F.isNegative(); } - bool isZero() const { return F.isZero(); } - bool isNonZero() const { return F.isNonZero(); } - bool isMin() const { return F.isSmallest(); } - bool isMinusOne() const { return F.isExactlyValue(-1.0); } - bool isNan() const { return F.isNaN(); } - bool isSignaling() const { return F.isSignaling(); } - bool isInf() const { return F.isInfinity(); } - bool isFinite() const { return F.isFinite(); } - bool isNormal() const { return F.isNormal(); } - bool isDenormal() const { return F.isDenormal(); } - llvm::FPClassTest classify() const { return F.classify(); } - APFloat::fltCategory getCategory() const { return F.getCategory(); } + bool isNegative() const { return getValue().isNegative(); } + bool isZero() const { return getValue().isZero(); } + bool isNonZero() const { return getValue().isNonZero(); } + bool isMin() const { return getValue().isSmallest(); } + bool isMinusOne() const { return getValue().isExactlyValue(-1.0); } + bool isNan() const { return getValue().isNaN(); } + bool isSignaling() const { return getValue().isSignaling(); } + bool isInf() const { return getValue().isInfinity(); } + bool isFinite() const { return getValue().isFinite(); } + bool isNormal() const { return getValue().isNormal(); } + bool isDenormal() const { return getValue().isDenormal(); } + llvm::FPClassTest classify() const { return getValue().classify(); } + APFloat::fltCategory getCategory() const { return getValue().getCategory(); } ComparisonCategoryResult compare(const Floating &RHS) const { - llvm::APFloatBase::cmpResult CmpRes = F.compare(RHS.F); + llvm::APFloatBase::cmpResult CmpRes = getValue().compare(RHS.getValue()); switch (CmpRes) { case llvm::APFloatBase::cmpLessThan: return ComparisonCategoryResult::Less; @@ -118,97 +172,130 @@ class Floating final { static APFloat::opStatus fromIntegral(APSInt Val, const llvm::fltSemantics &Sem, llvm::RoundingMode RM, - Floating &Result) { + Floating *Result) { APFloat F = APFloat(Sem); APFloat::opStatus Status = F.convertFromAPInt(Val, Val.isSigned(), RM); - Result = Floating(F); + Result->copy(F); return Status; } - static Floating bitcastFromMemory(const std::byte *Buff, - const llvm::fltSemantics &Sem) { + static void bitcastFromMemory(const std::byte *Buff, + const llvm::fltSemantics &Sem, + Floating *Result) { size_t Size = APFloat::semanticsSizeInBits(Sem); llvm::APInt API(Size, true); llvm::LoadIntFromMemory(API, (const uint8_t *)Buff, Size / 8); - - return Floating(APFloat(Sem, API)); + Result->copy(APFloat(Sem, API)); } void bitcastToMemory(std::byte *Buff) const { - llvm::APInt API = F.bitcastToAPInt(); + llvm::APInt API = getValue().bitcastToAPInt(); llvm::StoreIntToMemory(API, (uint8_t *)Buff, bitWidth() / 8); } // === Serialization support === size_t bytesToSerialize() const { - return sizeof(llvm::fltSemantics *) + - (APFloat::semanticsSizeInBits(F.getSemantics()) / 8); + return sizeof(Semantics) + (numWords() * sizeof(uint64_t)); } void serialize(std::byte *Buff) const { - // Semantics followed by an APInt. - *reinterpret_cast<const llvm::fltSemantics **>(Buff) = &F.getSemantics(); - - llvm::APInt API = F.bitcastToAPInt(); - llvm::StoreIntToMemory(API, (uint8_t *)(Buff + sizeof(void *)), - bitWidth() / 8); + std::memcpy(Buff, &Semantics, sizeof(Semantics)); + if (singleWord()) { + std::memcpy(Buff + sizeof(Semantics), &Val, sizeof(uint64_t)); + } else { + std::memcpy(Buff + sizeof(Semantics), Memory, + numWords() * sizeof(uint64_t)); + } } - static Floating deserialize(const std::byte *Buff) { - const llvm::fltSemantics *Sem; - std::memcpy((void *)&Sem, Buff, sizeof(void *)); - return bitcastFromMemory(Buff + sizeof(void *), *Sem); + static llvm::APFloatBase::Semantics + deserializeSemantics(const std::byte *Buff) { + return *reinterpret_cast<const llvm::APFloatBase::Semantics *>(Buff); } - static Floating abs(const Floating &F) { - APFloat V = F.F; - if (V.isNegative()) - V.changeSign(); - return Floating(V); + static void deserialize(const std::byte *Buff, Floating *Result) { + llvm::APFloatBase::Semantics Semantics; + std::memcpy(&Semantics, Buff, sizeof(Semantics)); + + unsigned BitWidth = llvm::APFloa... [truncated] `````````` </details> https://github.com/llvm/llvm-project/pull/144246 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
