1 files changed, 121 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/AsmPrinter/ErlangGCPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/ErlangGCPrinter.cpp
new file mode 100644
index 000000000000..3849644d1584
--- /dev/null
+++ b/llvm/lib/CodeGen/AsmPrinter/ErlangGCPrinter.cpp
@@ -0,0 +1,121 @@
+//===- ErlangGCPrinter.cpp - Erlang/OTP frametable emitter ----------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the compiler plugin that is used in order to emit
+// garbage collection information in a convenient layout for parsing and
+// loading in the Erlang/OTP runtime.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/CodeGen/AsmPrinter.h"
+#include "llvm/CodeGen/BuiltinGCs.h"
+#include "llvm/CodeGen/GCMetadata.h"
+#include "llvm/CodeGen/GCMetadataPrinter.h"
+#include "llvm/CodeGen/GCStrategy.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/Target/TargetLoweringObjectFile.h"
+
+using namespace llvm;
+
+namespace {
+
+class ErlangGCPrinter : public GCMetadataPrinter {
+public:
+  void finishAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override;
+};
+
+} // end anonymous namespace
+
+static GCMetadataPrinterRegistry::Add<ErlangGCPrinter>
+    X("erlang", "erlang-compatible garbage collector");
+
+void ErlangGCPrinter::finishAssembly(Module &M, GCModuleInfo &Info,
+                                     AsmPrinter &AP) {
+  MCStreamer &OS = *AP.OutStreamer;
+  unsigned IntPtrSize = M.getDataLayout().getPointerSize();
+
+  // Put this in a custom .note section.
+  OS.SwitchSection(
+      AP.getObjFileLowering().getContext().getELFSection(".note.gc",
+                                                         ELF::SHT_PROGBITS, 0));
+
+  // For each function...
+  for (GCModuleInfo::FuncInfoVec::iterator FI = Info.funcinfo_begin(),
+                                           IE = Info.funcinfo_end();
+       FI != IE; ++FI) {
+    GCFunctionInfo &MD = **FI;
+    if (MD.getStrategy().getName() != getStrategy().getName())
+      // this function is managed by some other GC
+      continue;
+    /** A compact GC layout. Emit this data structure:
+     *
+     * struct {
+     *   int16_t PointCount;
+     *   void *SafePointAddress[PointCount];
+     *   int16_t StackFrameSize; (in words)
+     *   int16_t StackArity;
+     *   int16_t LiveCount;
+     *   int16_t LiveOffsets[LiveCount];
+     * } __gcmap_<FUNCTIONNAME>;
+     **/
+
+    // Align to address width.
+    AP.EmitAlignment(IntPtrSize == 4 ? Align(4) : Align(8));
+
+    // Emit PointCount.
+    OS.AddComment("safe point count");
+    AP.emitInt16(MD.size());
+
+    // And each safe point...
+    for (GCFunctionInfo::iterator PI = MD.begin(), PE = MD.end(); PI != PE;
+         ++PI) {
+      // Emit the address of the safe point.
+      OS.AddComment("safe point address");
+      MCSymbol *Label = PI->Label;
+      AP.EmitLabelPlusOffset(Label /*Hi*/, 0 /*Offset*/, 4 /*Size*/);
+    }
+
+    // Stack information never change in safe points! Only print info from the
+    // first call-site.
+    GCFunctionInfo::iterator PI = MD.begin();
+
+    // Emit the stack frame size.
+    OS.AddComment("stack frame size (in words)");
+    AP.emitInt16(MD.getFrameSize() / IntPtrSize);
+
+    // Emit stack arity, i.e. the number of stacked arguments.
+    unsigned RegisteredArgs = IntPtrSize == 4 ? 5 : 6;
+    unsigned StackArity = MD.getFunction().arg_size() > RegisteredArgs
+                              ? MD.getFunction().arg_size() - RegisteredArgs
+                              : 0;
+    OS.AddComment("stack arity");
+    AP.emitInt16(StackArity);
+
+    // Emit the number of live roots in the function.
+    OS.AddComment("live root count");
+    AP.emitInt16(MD.live_size(PI));
+
+    // And for each live root...
+    for (GCFunctionInfo::live_iterator LI = MD.live_begin(PI),
+                                       LE = MD.live_end(PI);
+         LI != LE; ++LI) {
+      // Emit live root's offset within the stack frame.
+      OS.AddComment("stack index (offset / wordsize)");
+      AP.emitInt16(LI->StackOffset / IntPtrSize);
+    }
+  }
+}
+
+void llvm::linkErlangGCPrinter() {}