1 files changed, 175 insertions, 0 deletions
diff --git a/lib/AST/Interp/ByteCodeEmitter.cpp b/lib/AST/Interp/ByteCodeEmitter.cpp
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index 000000000000..7a4569820a1d
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+++ b/lib/AST/Interp/ByteCodeEmitter.cpp
@@ -0,0 +1,175 @@
+//===--- ByteCodeEmitter.cpp - Instruction emitter for the VM ---*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "ByteCodeEmitter.h"
+#include "Context.h"
+#include "Opcode.h"
+#include "Program.h"
+#include "clang/AST/DeclCXX.h"
+
+using namespace clang;
+using namespace clang::interp;
+
+using APSInt = llvm::APSInt;
+using Error = llvm::Error;
+
+Expected<Function *> ByteCodeEmitter::compileFunc(const FunctionDecl *F) {
+  // Do not try to compile undefined functions.
+  if (!F->isDefined(F) || (!F->hasBody() && F->willHaveBody()))
+    return nullptr;
+
+  // Set up argument indices.
+  unsigned ParamOffset = 0;
+  SmallVector<PrimType, 8> ParamTypes;
+  llvm::DenseMap<unsigned, Function::ParamDescriptor> ParamDescriptors;
+
+  // If the return is not a primitive, a pointer to the storage where the value
+  // is initialized in is passed as the first argument.
+  QualType Ty = F->getReturnType();
+  if (!Ty->isVoidType() && !Ctx.classify(Ty)) {
+    ParamTypes.push_back(PT_Ptr);
+    ParamOffset += align(primSize(PT_Ptr));
+  }
+
+  // Assign descriptors to all parameters.
+  // Composite objects are lowered to pointers.
+  for (const ParmVarDecl *PD : F->parameters()) {
+    PrimType Ty;
+    if (llvm::Optional<PrimType> T = Ctx.classify(PD->getType())) {
+      Ty = *T;
+    } else {
+      Ty = PT_Ptr;
+    }
+
+    Descriptor *Desc = P.createDescriptor(PD, Ty);
+    ParamDescriptors.insert({ParamOffset, {Ty, Desc}});
+    Params.insert({PD, ParamOffset});
+    ParamOffset += align(primSize(Ty));
+    ParamTypes.push_back(Ty);
+  }
+
+  // Create a handle over the emitted code.
+  Function *Func = P.createFunction(F, ParamOffset, std::move(ParamTypes),
+                                    std::move(ParamDescriptors));
+  // Compile the function body.
+  if (!F->isConstexpr() || !visitFunc(F)) {
+    // Return a dummy function if compilation failed.
+    if (BailLocation)
+      return llvm::make_error<ByteCodeGenError>(*BailLocation);
+    else
+      return Func;
+  } else {
+    // Create scopes from descriptors.
+    llvm::SmallVector<Scope, 2> Scopes;
+    for (auto &DS : Descriptors) {
+      Scopes.emplace_back(std::move(DS));
+    }
+
+    // Set the function's code.
+    Func->setCode(NextLocalOffset, std::move(Code), std::move(SrcMap),
+                  std::move(Scopes));
+    return Func;
+  }
+}
+
+Scope::Local ByteCodeEmitter::createLocal(Descriptor *D) {
+  NextLocalOffset += sizeof(Block);
+  unsigned Location = NextLocalOffset;
+  NextLocalOffset += align(D->getAllocSize());
+  return {Location, D};
+}
+
+void ByteCodeEmitter::emitLabel(LabelTy Label) {
+  const size_t Target = Code.size();
+  LabelOffsets.insert({Label, Target});
+  auto It = LabelRelocs.find(Label);
+  if (It != LabelRelocs.end()) {
+    for (unsigned Reloc : It->second) {
+      using namespace llvm::support;
+
+      /// Rewrite the operand of all jumps to this label.
+      void *Location = Code.data() + Reloc - sizeof(int32_t);
+      const int32_t Offset = Target - static_cast<int64_t>(Reloc);
+      endian::write<int32_t, endianness::native, 1>(Location, Offset);
+    }
+    LabelRelocs.erase(It);
+  }
+}
+
+int32_t ByteCodeEmitter::getOffset(LabelTy Label) {
+  // Compute the PC offset which the jump is relative to.
+  const int64_t Position = Code.size() + sizeof(Opcode) + sizeof(int32_t);
+
+  // If target is known, compute jump offset.
+  auto It = LabelOffsets.find(Label);
+  if (It != LabelOffsets.end()) {
+    return It->second - Position;
+  }
+
+  // Otherwise, record relocation and return dummy offset.
+  LabelRelocs[Label].push_back(Position);
+  return 0ull;
+}
+
+bool ByteCodeEmitter::bail(const SourceLocation &Loc) {
+  if (!BailLocation)
+    BailLocation = Loc;
+  return false;
+}
+
+template <typename... Tys>
+bool ByteCodeEmitter::emitOp(Opcode Op, const Tys &... Args, const SourceInfo &SI) {
+  bool Success = true;
+
+  /// Helper to write bytecode and bail out if 32-bit offsets become invalid.
+  auto emit = [this, &Success](const char *Data, size_t Size) {
+    if (Code.size() + Size > std::numeric_limits<unsigned>::max()) {
+      Success = false;
+      return;
+    }
+    Code.insert(Code.end(), Data, Data + Size);
+  };
+
+  /// The opcode is followed by arguments. The source info is
+  /// attached to the address after the opcode.
+  emit(reinterpret_cast<const char *>(&Op), sizeof(Opcode));
+  if (SI)
+    SrcMap.emplace_back(Code.size(), SI);
+
+  /// The initializer list forces the expression to be evaluated
+  /// for each argument in the variadic template, in order.
+  (void)std::initializer_list<int>{
+      (emit(reinterpret_cast<const char *>(&Args), sizeof(Args)), 0)...};
+
+  return Success;
+}
+
+bool ByteCodeEmitter::jumpTrue(const LabelTy &Label) {
+  return emitJt(getOffset(Label), SourceInfo{});
+}
+
+bool ByteCodeEmitter::jumpFalse(const LabelTy &Label) {
+  return emitJf(getOffset(Label), SourceInfo{});
+}
+
+bool ByteCodeEmitter::jump(const LabelTy &Label) {
+  return emitJmp(getOffset(Label), SourceInfo{});
+}
+
+bool ByteCodeEmitter::fallthrough(const LabelTy &Label) {
+  emitLabel(Label);
+  return true;
+}
+
+//===----------------------------------------------------------------------===//
+// Opcode emitters
+//===----------------------------------------------------------------------===//
+
+#define GET_LINK_IMPL
+#include "Opcodes.inc"
+#undef GET_LINK_IMPL