[WebAssembly] Basic support for Wasm object file encoding.

With the "wasm32-unknown-unknown-wasm" triple, this allows writing out
simple wasm object files, and is another step in a larger series toward
migrating from ELF to general wasm object support. Note that this code
and the binary format itself is still experimental.

llvm-svn: 296190

7 files changed, 213 insertions, 41 deletions

diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp
index 337c18ca57d..5b210742063 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp
@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "MCTargetDesc/WebAssemblyFixupKinds.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCDirectives.h"
@@ -70,6 +71,12 @@ public:
       : MCAsmBackend(), Is64Bit(Is64Bit) {}
   ~WebAssemblyAsmBackend() override {}
 
+  unsigned getNumFixupKinds() const override {
+    return WebAssembly::NumTargetFixupKinds;
+  }
+
+  const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
+
   void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
                   uint64_t Value, bool IsPCRel) const override;
 
@@ -82,12 +89,6 @@ public:
     return false;
   }
 
-  unsigned getNumFixupKinds() const override {
-    // We currently just use the generic fixups in MCFixup.h and don't have any
-    // target-specific fixups.
-    return 0;
-  }
-
   bool mayNeedRelaxation(const MCInst &Inst) const override { return false; }
 
   void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
@@ -131,6 +132,26 @@ WebAssemblyAsmBackendELF::createObjectWriter(raw_pwrite_stream &OS) const {
   return createWebAssemblyELFObjectWriter(OS, Is64Bit, 0);
 }
 
+const MCFixupKindInfo &
+WebAssemblyAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
+  const static MCFixupKindInfo Infos[WebAssembly::NumTargetFixupKinds] = {
+    // This table *must* be in the order that the fixup_* kinds are defined in
+    // WebAssemblyFixupKinds.h.
+    //
+    // Name                     Offset (bits) Size (bits)     Flags
+    { "fixup_code_sleb128_i32", 0,            5*8,            0 },
+    { "fixup_code_sleb128_i64", 0,            10*8,           0 },
+    { "fixup_code_uleb128_i32", 0,            5*8,            0 },
+  };
+
+  if (Kind < FirstTargetFixupKind)
+    return MCAsmBackend::getFixupKindInfo(Kind);
+
+  assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
+         "Invalid kind!");
+  return Infos[Kind - FirstTargetFixupKind];
+}
+
 bool WebAssemblyAsmBackend::writeNopData(uint64_t Count,
                                          MCObjectWriter *OW) const {
   if (Count == 0)
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyFixupKinds.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyFixupKinds.h
new file mode 100644
index 00000000000..b0af63c924b
--- /dev/null
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyFixupKinds.h
@@ -0,0 +1,31 @@
+//=- WebAssemblyFixupKinds.h - WebAssembly Specific Fixup Entries -*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_WEBASSEMBLY_MCTARGETDESC_WEBASSEMBLYFIXUPKINDS_H
+#define LLVM_LIB_TARGET_WEBASSEMBLY_MCTARGETDESC_WEBASSEMBLYFIXUPKINDS_H
+
+#include "llvm/MC/MCFixup.h"
+
+namespace llvm {
+namespace WebAssembly {
+enum Fixups {
+  fixup_code_sleb128_i32 = FirstTargetFixupKind,      // 32-bit signed
+  fixup_code_sleb128_i64,                             // 64-bit signed
+  fixup_code_uleb128_i32,                             // 32-bit unsigned
+
+  fixup_code_global_index,                            // 32-bit unsigned
+
+  // Marker
+  LastTargetFixupKind,
+  NumTargetFixupKinds = LastTargetFixupKind - FirstTargetFixupKind
+};
+} // end namespace WebAssembly
+} // end namespace llvm
+
+#endif
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCCodeEmitter.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCCodeEmitter.cpp
index 91583ef119e..a0b00894749 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCCodeEmitter.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCCodeEmitter.cpp
@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "MCTargetDesc/WebAssemblyFixupKinds.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/MC/MCCodeEmitter.h"
@@ -48,9 +49,7 @@ class WebAssemblyMCCodeEmitter final : public MCCodeEmitter {
 
 public:
   WebAssemblyMCCodeEmitter(const MCInstrInfo &mcii, MCContext &ctx)
-      : MCII(mcii), Ctx(ctx) {
-    (void)Ctx;
-  }
+      : MCII(mcii), Ctx(ctx) {}
 };
 } // end anonymous namespace
 
@@ -68,6 +67,13 @@ void WebAssemblyMCCodeEmitter::encodeInstruction(
   assert(Binary < UINT8_MAX && "Multi-byte opcodes not supported yet");
   OS << uint8_t(Binary);
 
+  // For br_table instructions, encode the size of the table. In the MCInst,
+  // there's an index operand, one operand for each table entry, and the
+  // default operand.
+  if (MI.getOpcode() == WebAssembly::BR_TABLE_I32 ||
+      MI.getOpcode() == WebAssembly::BR_TABLE_I64)
+    encodeULEB128(MI.getNumOperands() - 2, OS);
+
   const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
   for (unsigned i = 0, e = MI.getNumOperands(); i < e; ++i) {
     const MCOperand &MO = MI.getOperand(i);
@@ -82,6 +88,12 @@ void WebAssemblyMCCodeEmitter::encodeInstruction(
           encodeSLEB128(int32_t(MO.getImm()), OS);
         } else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) {
           encodeSLEB128(int64_t(MO.getImm()), OS);
+        } else if (Info.OperandType == WebAssembly::OPERAND_GLOBAL) {
+          Fixups.push_back(MCFixup::create(
+              OS.tell() - Start, MCConstantExpr::create(MO.getImm(), Ctx),
+              MCFixupKind(WebAssembly::fixup_code_global_index), MI.getLoc()));
+          ++MCNumFixups;
+          encodeULEB128(uint64_t(MO.getImm()), OS);
         } else {
           encodeULEB128(uint64_t(MO.getImm()), OS);
         }
@@ -107,14 +119,28 @@ void WebAssemblyMCCodeEmitter::encodeInstruction(
         support::endian::Writer<support::little>(OS).write<double>(d);
       }
     } else if (MO.isExpr()) {
+      const MCOperandInfo &Info = Desc.OpInfo[i];
+      llvm::MCFixupKind FixupKind;
+      size_t PaddedSize;
+      if (Info.OperandType == WebAssembly::OPERAND_I32IMM) {
+        FixupKind = MCFixupKind(WebAssembly::fixup_code_sleb128_i32);
+        PaddedSize = 5;
+      } else if (Info.OperandType == WebAssembly::OPERAND_I64IMM) {
+        FixupKind = MCFixupKind(WebAssembly::fixup_code_sleb128_i64);
+        PaddedSize = 10;
+      } else if (Info.OperandType == WebAssembly::OPERAND_FUNCTION32 ||
+                 Info.OperandType == WebAssembly::OPERAND_OFFSET32 ||
+                 Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
+        FixupKind = MCFixupKind(WebAssembly::fixup_code_uleb128_i32);
+        PaddedSize = 5;
+      } else {
+        llvm_unreachable("unexpected symbolic operand kind");
+      }
       Fixups.push_back(MCFixup::create(
           OS.tell() - Start, MO.getExpr(),
-          STI.getTargetTriple().isArch64Bit() ? FK_Data_8 : FK_Data_4,
-          MI.getLoc()));
+          FixupKind, MI.getLoc()));
       ++MCNumFixups;
-      encodeULEB128(STI.getTargetTriple().isArch64Bit() ? UINT64_MAX
-                                                        : uint64_t(UINT32_MAX),
-                    OS);
+      encodeULEB128(0, OS, PaddedSize - 1);
     } else {
       llvm_unreachable("unexpected operand kind");
     }
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
index 93ad57407e2..1108f5f5a32 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
@@ -68,7 +68,9 @@ enum OperandType {
   /// p2align immediate for load and store address alignment.
   OPERAND_P2ALIGN,
   /// signature immediate for block/loop.
-  OPERAND_SIGNATURE
+  OPERAND_SIGNATURE,
+  /// type signature immediate for call_indirect.
+  OPERAND_TYPEINDEX,
 };
 } // end namespace WebAssembly
 
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
index b8a0f589d7f..c198a262241 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
@@ -22,8 +22,10 @@
 #include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/MC/MCSymbolELF.h"
 #include "llvm/MC/MCSymbolWasm.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FormattedStream.h"
+#include "llvm/Support/Wasm.h"
 using namespace llvm;
 
 WebAssemblyTargetStreamer::WebAssemblyTargetStreamer(MCStreamer &S)
@@ -51,14 +53,28 @@ static void PrintTypes(formatted_raw_ostream &OS, ArrayRef<MVT> Types) {
   OS << '\n';
 }
 
-void WebAssemblyTargetAsmStreamer::emitParam(ArrayRef<MVT> Types) {
-  OS << "\t.param  \t";
-  PrintTypes(OS, Types);
+void WebAssemblyTargetAsmStreamer::emitParam(MCSymbol *Symbol,
+                                             ArrayRef<MVT> Types) {
+  if (!Types.empty()) {
+    OS << "\t.param  \t";
+
+    // FIXME: Currently this applies to the "current" function; it may
+    // be cleaner to specify an explicit symbol as part of the directive.
+
+    PrintTypes(OS, Types);
+  }
 }
 
-void WebAssemblyTargetAsmStreamer::emitResult(ArrayRef<MVT> Types) {
-  OS << "\t.result \t";
-  PrintTypes(OS, Types);
+void WebAssemblyTargetAsmStreamer::emitResult(MCSymbol *Symbol,
+                                              ArrayRef<MVT> Types) {
+  if (!Types.empty()) {
+    OS << "\t.result \t";
+
+    // FIXME: Currently this applies to the "current" function; it may
+    // be cleaner to specify an explicit symbol as part of the directive.
+
+    PrintTypes(OS, Types);
+  }
 }
 
 void WebAssemblyTargetAsmStreamer::emitLocal(ArrayRef<MVT> Types) {
@@ -92,11 +108,13 @@ void WebAssemblyTargetAsmStreamer::emitIndIdx(const MCExpr *Value) {
   OS << "\t.indidx  \t" << *Value << '\n';
 }
 
-void WebAssemblyTargetELFStreamer::emitParam(ArrayRef<MVT> Types) {
+void WebAssemblyTargetELFStreamer::emitParam(MCSymbol *Symbol,
+                                             ArrayRef<MVT> Types) {
   // Nothing to emit; params are declared as part of the function signature.
 }
 
-void WebAssemblyTargetELFStreamer::emitResult(ArrayRef<MVT> Types) {
+void WebAssemblyTargetELFStreamer::emitResult(MCSymbol *Symbol,
+                                              ArrayRef<MVT> Types) {
   // Nothing to emit; results are declared as part of the function signature.
 }
 
@@ -123,22 +141,52 @@ void WebAssemblyTargetELFStreamer::emitIndirectFunctionType(
 void WebAssemblyTargetELFStreamer::emitGlobalImport(StringRef name) {
 }
 
-void WebAssemblyTargetWasmStreamer::emitParam(ArrayRef<MVT> Types) {
-  // Nothing to emit; params are declared as part of the function signature.
+static unsigned MVT2WasmType(MVT Ty) {
+  switch (Ty.SimpleTy) {
+  case MVT::i32: return wasm::WASM_TYPE_I32;
+  case MVT::i64: return wasm::WASM_TYPE_I64;
+  case MVT::f32: return wasm::WASM_TYPE_F32;
+  case MVT::f64: return wasm::WASM_TYPE_F64;
+  default: llvm_unreachable("unsupported type");
+  }
 }
 
-void WebAssemblyTargetWasmStreamer::emitResult(ArrayRef<MVT> Types) {
-  // Nothing to emit; results are declared as part of the function signature.
+void WebAssemblyTargetWasmStreamer::emitParam(MCSymbol *Symbol,
+                                              ArrayRef<MVT> Types) {
+  SmallVector<unsigned, 4> Params;
+  for (MVT Ty : Types)
+    Params.push_back(MVT2WasmType(Ty));
+
+  cast<MCSymbolWasm>(Symbol)->setParams(std::move(Params));
+}
+
+void WebAssemblyTargetWasmStreamer::emitResult(MCSymbol *Symbol,
+                                               ArrayRef<MVT> Types) {
+  SmallVector<unsigned, 4> Returns;
+  for (MVT Ty : Types)
+    Returns.push_back(MVT2WasmType(Ty));
+
+  cast<MCSymbolWasm>(Symbol)->setReturns(std::move(Returns));
 }
 
 void WebAssemblyTargetWasmStreamer::emitLocal(ArrayRef<MVT> Types) {
-  Streamer.EmitULEB128IntValue(Types.size());
-  for (MVT Type : Types)
-    Streamer.EmitIntValue(int64_t(WebAssembly::toValType(Type)), 1);
+  SmallVector<std::pair<MVT, uint32_t>, 4> Grouped;
+  for (MVT Type : Types) {
+    if (Grouped.empty() || Grouped.back().first != Type)
+      Grouped.push_back(std::make_pair(Type, 1));
+    else
+      ++Grouped.back().second;
+  }
+
+  Streamer.EmitULEB128IntValue(Grouped.size());
+  for (auto Pair : Grouped) {
+    Streamer.EmitULEB128IntValue(Pair.second);
+    Streamer.EmitULEB128IntValue(uint64_t(WebAssembly::toValType(Pair.first)));
+  }
 }
 
 void WebAssemblyTargetWasmStreamer::emitEndFunc() {
-  Streamer.EmitIntValue(WebAssembly::End, 1);
+  llvm_unreachable(".end_func is not needed for direct wasm output");
 }
 
 void WebAssemblyTargetWasmStreamer::emitIndIdx(const MCExpr *Value) {
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
index 35b14bc0ba5..1ad3ffcf408 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
@@ -31,9 +31,9 @@ public:
   explicit WebAssemblyTargetStreamer(MCStreamer &S);
 
   /// .param
-  virtual void emitParam(ArrayRef<MVT> Types) = 0;
+  virtual void emitParam(MCSymbol *Symbol, ArrayRef<MVT> Types) = 0;
   /// .result
-  virtual void emitResult(ArrayRef<MVT> Types) = 0;
+  virtual void emitResult(MCSymbol *Symbol, ArrayRef<MVT> Types) = 0;
   /// .local
   virtual void emitLocal(ArrayRef<MVT> Types) = 0;
   /// .endfunc
@@ -57,8 +57,8 @@ class WebAssemblyTargetAsmStreamer final : public WebAssemblyTargetStreamer {
 public:
   WebAssemblyTargetAsmStreamer(MCStreamer &S, formatted_raw_ostream &OS);
 
-  void emitParam(ArrayRef<MVT> Types) override;
-  void emitResult(ArrayRef<MVT> Types) override;
+  void emitParam(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
+  void emitResult(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitLocal(ArrayRef<MVT> Types) override;
   void emitEndFunc() override;
   void emitIndirectFunctionType(StringRef name,
@@ -73,8 +73,8 @@ class WebAssemblyTargetELFStreamer final : public WebAssemblyTargetStreamer {
 public:
   explicit WebAssemblyTargetELFStreamer(MCStreamer &S);
 
-  void emitParam(ArrayRef<MVT> Types) override;
-  void emitResult(ArrayRef<MVT> Types) override;
+  void emitParam(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
+  void emitResult(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitLocal(ArrayRef<MVT> Types) override;
   void emitEndFunc() override;
   void emitIndirectFunctionType(StringRef name,
@@ -89,8 +89,8 @@ class WebAssemblyTargetWasmStreamer final : public WebAssemblyTargetStreamer {
 public:
   explicit WebAssemblyTargetWasmStreamer(MCStreamer &S);
 
-  void emitParam(ArrayRef<MVT> Types) override;
-  void emitResult(ArrayRef<MVT> Types) override;
+  void emitParam(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
+  void emitResult(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitLocal(ArrayRef<MVT> Types) override;
   void emitEndFunc() override;
   void emitIndirectFunctionType(StringRef name,
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
index 3fb3e65fb91..2846ec5e933 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyWasmObjectWriter.cpp
@@ -14,9 +14,13 @@
 //===----------------------------------------------------------------------===//
 
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "MCTargetDesc/WebAssemblyFixupKinds.h"
 #include "llvm/MC/MCFixup.h"
+#include "llvm/MC/MCSymbolWasm.h"
 #include "llvm/MC/MCWasmObjectWriter.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/Wasm.h"
 using namespace llvm;
 
 namespace {
@@ -33,12 +37,52 @@ private:
 WebAssemblyWasmObjectWriter::WebAssemblyWasmObjectWriter(bool Is64Bit)
     : MCWasmObjectTargetWriter(Is64Bit) {}
 
+// Test whether the given expression computes a function address.
+static bool IsFunctionExpr(const MCExpr *Expr) {
+  if (const MCSymbolRefExpr *SyExp =
+          dyn_cast<MCSymbolRefExpr>(Expr))
+    return cast<MCSymbolWasm>(SyExp->getSymbol()).isFunction();
+
+  if (const MCBinaryExpr *BinOp =
+          dyn_cast<MCBinaryExpr>(Expr))
+    return IsFunctionExpr(BinOp->getLHS()) != IsFunctionExpr(BinOp->getRHS());
+
+  if (const MCUnaryExpr *UnOp =
+          dyn_cast<MCUnaryExpr>(Expr))
+    return IsFunctionExpr(UnOp->getSubExpr());
+
+  return false;
+}
+
 unsigned WebAssemblyWasmObjectWriter::getRelocType(MCContext &Ctx,
                                                    const MCValue &Target,
                                                    const MCFixup &Fixup,
                                                    bool IsPCRel) const {
-  llvm_unreachable("Relocations not yet implemented");
-  return 0;
+  // WebAssembly functions are not allocated in the data address space. To
+  // resolve a pointer to a function, we must use a special relocation type.
+  bool IsFunction = IsFunctionExpr(Fixup.getValue());
+
+  assert(!IsPCRel);
+  switch (unsigned(Fixup.getKind())) {
+  case WebAssembly::fixup_code_sleb128_i32:
+    if (IsFunction)
+      return wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB;
+    return wasm::R_WEBASSEMBLY_GLOBAL_ADDR_SLEB;
+  case WebAssembly::fixup_code_sleb128_i64:
+    llvm_unreachable("fixup_sleb128_i64 not implemented yet");
+  case WebAssembly::fixup_code_uleb128_i32:
+    if (IsFunction)
+      return wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB;
+    return wasm::R_WEBASSEMBLY_GLOBAL_ADDR_LEB;
+  case FK_Data_4:
+    if (IsFunction)
+      return wasm::R_WEBASSEMBLY_TABLE_INDEX_I32;
+    return wasm::R_WEBASSEMBLY_GLOBAL_ADDR_I32;
+  case FK_Data_8:
+    llvm_unreachable("FK_Data_8 not implemented yet");
+  default:
+    llvm_unreachable("unimplemented fixup kind");
+  }
 }
 
 MCObjectWriter *llvm::createWebAssemblyWasmObjectWriter(raw_pwrite_stream &OS,