[WebAssembly] Add support for using a wasm global for the stack pointer.

This replaces the __stack_pointer variable which was allocated in linear
memory.

llvm-svn: 296201

7 files changed, 137 insertions, 42 deletions

diff --git a/llvm/lib/CodeGen/MachineModuleInfoImpls.cpp b/llvm/lib/CodeGen/MachineModuleInfoImpls.cpp
index 22d519e5d88..4c81fd91cb8 100644
--- a/llvm/lib/CodeGen/MachineModuleInfoImpls.cpp
+++ b/llvm/lib/CodeGen/MachineModuleInfoImpls.cpp
@@ -23,6 +23,7 @@ using namespace llvm;
 // Out of line virtual method.
 void MachineModuleInfoMachO::anchor() {}
 void MachineModuleInfoELF::anchor() {}
+void MachineModuleInfoWasm::anchor() {}
 
 static int SortSymbolPair(const void *LHS, const void *RHS) {
   typedef std::pair<MCSymbol*, MachineModuleInfoImpl::StubValueTy> PairTy;
diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 32d8b8c4de9..9c0a593592c 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -504,6 +504,7 @@ static void WriteRelocations(
 
 void WasmObjectWriter::writeObject(MCAssembler &Asm,
                                    const MCAsmLayout &Layout) {
+  MCContext &Ctx = Asm.getContext();
   unsigned PtrType = is64Bit() ? wasm::WASM_TYPE_I64 : wasm::WASM_TYPE_I32;
 
   // Collect information from the available symbols.
@@ -585,6 +586,29 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
     }
   }
 
+  // In the special .global_variables section, we've encoded global
+  // variables used by the function. Translate them into the Globals
+  // list.
+  MCSectionWasm *GlobalVars = Ctx.getWasmSection(".global_variables", 0, 0);
+  if (!GlobalVars->getFragmentList().empty()) {
+    if (GlobalVars->getFragmentList().size() != 1)
+      report_fatal_error("only one .global_variables fragment supported");
+    const MCFragment &Frag = *GlobalVars->begin();
+    if (Frag.hasInstructions() || Frag.getKind() != MCFragment::FT_Data)
+      report_fatal_error("only data supported in .global_variables");
+    const MCDataFragment &DataFrag = cast<MCDataFragment>(Frag);
+    if (!DataFrag.getFixups().empty())
+      report_fatal_error("fixups not supported in .global_variables");
+    const SmallVectorImpl<char> &Contents = DataFrag.getContents();
+    for (char p : Contents) {
+      WasmGlobal G;
+      G.Type = uint8_t(p);
+      G.IsMutable = true;
+      G.InitialValue = 0;
+      Globals.push_back(G);
+    }
+  }
+
   // Handle defined symbols.
   for (const MCSymbol &S : Asm.symbols()) {
     // Ignore unnamed temporary symbols, which aren't ever exported, imported,
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
index c198a262241..5a285935e2b 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
@@ -84,6 +84,13 @@ void WebAssemblyTargetAsmStreamer::emitLocal(ArrayRef<MVT> Types) {
   }
 }
 
+void WebAssemblyTargetAsmStreamer::emitGlobal(ArrayRef<MVT> Types) {
+  if (!Types.empty()) {
+    OS << "\t.globalvar  \t";
+    PrintTypes(OS, Types);
+  }
+}
+
 void WebAssemblyTargetAsmStreamer::emitEndFunc() { OS << "\t.endfunc\n"; }
 
 void WebAssemblyTargetAsmStreamer::emitIndirectFunctionType(
@@ -124,6 +131,10 @@ void WebAssemblyTargetELFStreamer::emitLocal(ArrayRef<MVT> Types) {
     Streamer.EmitIntValue(int64_t(WebAssembly::toValType(Type)), 1);
 }
 
+void WebAssemblyTargetELFStreamer::emitGlobal(ArrayRef<MVT> Types) {
+  llvm_unreachable(".globalvar encoding not yet implemented");
+}
+
 void WebAssemblyTargetELFStreamer::emitEndFunc() {
   Streamer.EmitIntValue(WebAssembly::End, 1);
 }
@@ -185,6 +196,18 @@ void WebAssemblyTargetWasmStreamer::emitLocal(ArrayRef<MVT> Types) {
   }
 }
 
+void WebAssemblyTargetWasmStreamer::emitGlobal(ArrayRef<MVT> Types) {
+  // Encode the globals use by the funciton into the special .global_variables
+  // section. This will later be decoded and turned into contents for the
+  // Globals Section.
+  Streamer.PushSection();
+  Streamer.SwitchSection(Streamer.getContext()
+                                 .getWasmSection(".global_variables", 0, 0));
+  for (MVT Ty : Types)
+    Streamer.EmitIntValue(uint64_t(WebAssembly::toValType(Ty)), 1);
+  Streamer.PopSection();
+}
+
 void WebAssemblyTargetWasmStreamer::emitEndFunc() {
   llvm_unreachable(".end_func is not needed for direct wasm output");
 }
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
index 1ad3ffcf408..92bb949b654 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
@@ -36,6 +36,8 @@ public:
   virtual void emitResult(MCSymbol *Symbol, ArrayRef<MVT> Types) = 0;
   /// .local
   virtual void emitLocal(ArrayRef<MVT> Types) = 0;
+  /// .globalvar
+  virtual void emitGlobal(ArrayRef<MVT> Types) = 0;
   /// .endfunc
   virtual void emitEndFunc() = 0;
   /// .functype
@@ -60,6 +62,7 @@ public:
   void emitParam(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitResult(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitLocal(ArrayRef<MVT> Types) override;
+  void emitGlobal(ArrayRef<MVT> Types) override;
   void emitEndFunc() override;
   void emitIndirectFunctionType(StringRef name,
                                 SmallVectorImpl<MVT> &Params,
@@ -76,6 +79,7 @@ public:
   void emitParam(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitResult(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitLocal(ArrayRef<MVT> Types) override;
+  void emitGlobal(ArrayRef<MVT> Types) override;
   void emitEndFunc() override;
   void emitIndirectFunctionType(StringRef name,
                                 SmallVectorImpl<MVT> &Params,
@@ -92,6 +96,7 @@ public:
   void emitParam(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitResult(MCSymbol *Symbol, ArrayRef<MVT> Types) override;
   void emitLocal(ArrayRef<MVT> Types) override;
+  void emitGlobal(ArrayRef<MVT> Types) override;
   void emitEndFunc() override;
   void emitIndirectFunctionType(StringRef name,
                                 SmallVectorImpl<MVT> &Params,
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
index 56bb550c72f..c272eb4cbf5 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
@@ -27,6 +27,7 @@
 #include "llvm/CodeGen/AsmPrinter.h"
 #include "llvm/CodeGen/MachineConstantPool.h"
 #include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineModuleInfoImpls.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/MC/MCContext.h"
@@ -92,6 +93,11 @@ void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
                                MCConstantExpr::create(Size, OutContext));
     }
   }
+
+  if (!TM.getTargetTriple().isOSBinFormatELF()) {
+    MachineModuleInfoWasm &MMIW = MMI->getObjFileInfo<MachineModuleInfoWasm>();
+    getTargetStreamer()->emitGlobal(MMIW.getGlobals());
+  }
 }
 
 void WebAssemblyAsmPrinter::EmitConstantPool() {
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
index b325b0953d0..8b25285ad0d 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
@@ -28,7 +28,7 @@
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
-#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/MachineModuleInfoImpls.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/Support/Debug.h"
 using namespace llvm;
@@ -102,25 +102,35 @@ static void writeSPToMemory(unsigned SrcReg, MachineFunction &MF,
                             MachineBasicBlock::iterator &InsertAddr,
                             MachineBasicBlock::iterator &InsertStore,
                             const DebugLoc &DL) {
-  const char *ES = "__stack_pointer";
-  auto *SPSymbol = MF.createExternalSymbolName(ES);
-  MachineRegisterInfo &MRI = MF.getRegInfo();
-  const TargetRegisterClass *PtrRC =
-      MRI.getTargetRegisterInfo()->getPointerRegClass(MF);
-  unsigned Zero = MRI.createVirtualRegister(PtrRC);
   const auto *TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
 
-  BuildMI(MBB, InsertAddr, DL, TII->get(WebAssembly::CONST_I32), Zero)
-      .addImm(0);
-  MachineMemOperand *MMO = MF.getMachineMemOperand(
-      MachinePointerInfo(MF.getPSVManager().getExternalSymbolCallEntry(ES)),
-      MachineMemOperand::MOStore, 4, 4);
-  BuildMI(MBB, InsertStore, DL, TII->get(WebAssembly::STORE_I32))
-      .addImm(2)  // p2align
-      .addExternalSymbol(SPSymbol)
-      .addReg(Zero)
-      .addReg(SrcReg)
-      .addMemOperand(MMO);
+  if (MF.getSubtarget<WebAssemblySubtarget>()
+        .getTargetTriple().isOSBinFormatELF()) {
+    const char *ES = "__stack_pointer";
+    auto *SPSymbol = MF.createExternalSymbolName(ES);
+    MachineRegisterInfo &MRI = MF.getRegInfo();
+    const TargetRegisterClass *PtrRC =
+        MRI.getTargetRegisterInfo()->getPointerRegClass(MF);
+    unsigned Zero = MRI.createVirtualRegister(PtrRC);
+
+    BuildMI(MBB, InsertAddr, DL, TII->get(WebAssembly::CONST_I32), Zero)
+        .addImm(0);
+    MachineMemOperand *MMO = MF.getMachineMemOperand(
+        MachinePointerInfo(MF.getPSVManager().getExternalSymbolCallEntry(ES)),
+        MachineMemOperand::MOStore, 4, 4);
+    BuildMI(MBB, InsertStore, DL, TII->get(WebAssembly::STORE_I32))
+        .addImm(2)  // p2align
+        .addExternalSymbol(SPSymbol)
+        .addReg(Zero)
+        .addReg(SrcReg)
+        .addMemOperand(MMO);
+  } else {
+    MachineModuleInfoWasm &MMIW =
+        MF.getMMI().getObjFileInfo<MachineModuleInfoWasm>();
+    BuildMI(MBB, InsertStore, DL, TII->get(WebAssembly::SET_GLOBAL_I32))
+        .addImm(MMIW.getStackPointerGlobal())
+        .addReg(SrcReg);
+  }
 }
 
 MachineBasicBlock::iterator
@@ -158,23 +168,35 @@ void WebAssemblyFrameLowering::emitPrologue(MachineFunction &MF,
 
   const TargetRegisterClass *PtrRC =
       MRI.getTargetRegisterInfo()->getPointerRegClass(MF);
-  unsigned Zero = MRI.createVirtualRegister(PtrRC);
   unsigned SPReg = WebAssembly::SP32;
   if (StackSize)
     SPReg = MRI.createVirtualRegister(PtrRC);
-  const char *ES = "__stack_pointer";
-  auto *SPSymbol = MF.createExternalSymbolName(ES);
-  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), Zero)
-      .addImm(0);
-  MachineMemOperand *LoadMMO = MF.getMachineMemOperand(
-      MachinePointerInfo(MF.getPSVManager().getExternalSymbolCallEntry(ES)),
-      MachineMemOperand::MOLoad, 4, 4);
-  // Load the SP value.
-  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::LOAD_I32), SPReg)
-      .addImm(2)       // p2align
-      .addExternalSymbol(SPSymbol)
-      .addReg(Zero)    // addr
-      .addMemOperand(LoadMMO);
+  if (MF.getSubtarget<WebAssemblySubtarget>()
+        .getTargetTriple().isOSBinFormatELF()) {
+    const char *ES = "__stack_pointer";
+    auto *SPSymbol = MF.createExternalSymbolName(ES);
+    unsigned Zero = MRI.createVirtualRegister(PtrRC);
+
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), Zero)
+        .addImm(0);
+    MachineMemOperand *LoadMMO = MF.getMachineMemOperand(
+        MachinePointerInfo(MF.getPSVManager().getExternalSymbolCallEntry(ES)),
+        MachineMemOperand::MOLoad, 4, 4);
+    // Load the SP value.
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::LOAD_I32), SPReg)
+        .addImm(2)       // p2align
+        .addExternalSymbol(SPSymbol)
+        .addReg(Zero)    // addr
+        .addMemOperand(LoadMMO);
+  } else {
+    auto &MMIW = MF.getMMI().getObjFileInfo<MachineModuleInfoWasm>();
+    if (!MMIW.hasStackPointerGlobal()) {
+      MMIW.setStackPointerGlobal(MMIW.getGlobals().size());
+      MMIW.addGlobal(MVT::i32);
+    }
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::GET_GLOBAL_I32), SPReg)
+        .addImm(MMIW.getStackPointerGlobal());
+  }
 
   bool HasBP = hasBP(MF);
   if (HasBP) {
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
index 32ee09e4579..57d454746b0 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
@@ -30,6 +30,7 @@
 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineModuleInfoImpls.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/Support/Debug.h"
@@ -152,7 +153,7 @@ static void QueryCallee(const MachineInstr &MI, unsigned CalleeOpNo, bool &Read,
 }
 
 // Determine whether MI reads memory, writes memory, has side effects,
-// and/or uses the __stack_pointer value.
+// and/or uses the stack pointer value.
 static void Query(const MachineInstr &MI, AliasAnalysis &AA, bool &Read,
                   bool &Write, bool &Effects, bool &StackPointer) {
   assert(!MI.isPosition());
@@ -169,15 +170,28 @@ static void Query(const MachineInstr &MI, AliasAnalysis &AA, bool &Read,
   if (MI.mayStore()) {
     Write = true;
 
-    // Check for stores to __stack_pointer.
-    for (auto MMO : MI.memoperands()) {
-      const MachinePointerInfo &MPI = MMO->getPointerInfo();
-      if (MPI.V.is<const PseudoSourceValue *>()) {
-        auto PSV = MPI.V.get<const PseudoSourceValue *>();
-        if (const ExternalSymbolPseudoSourceValue *EPSV =
-                dyn_cast<ExternalSymbolPseudoSourceValue>(PSV))
-          if (StringRef(EPSV->getSymbol()) == "__stack_pointer")
-            StackPointer = true;
+    const MachineFunction &MF = *MI.getParent()->getParent();
+    if (MF.getSubtarget<WebAssemblySubtarget>()
+          .getTargetTriple().isOSBinFormatELF()) {
+      // Check for stores to __stack_pointer.
+      for (auto MMO : MI.memoperands()) {
+        const MachinePointerInfo &MPI = MMO->getPointerInfo();
+        if (MPI.V.is<const PseudoSourceValue *>()) {
+          auto PSV = MPI.V.get<const PseudoSourceValue *>();
+          if (const ExternalSymbolPseudoSourceValue *EPSV =
+                  dyn_cast<ExternalSymbolPseudoSourceValue>(PSV))
+            if (StringRef(EPSV->getSymbol()) == "__stack_pointer")
+              StackPointer = true;
+        }
+      }
+    } else {
+      // Check for sets of the stack pointer.
+      const MachineModuleInfoWasm &MMIW =
+          MF.getMMI().getObjFileInfo<MachineModuleInfoWasm>();
+      if ((MI.getOpcode() == WebAssembly::SET_LOCAL_I32 ||
+           MI.getOpcode() == WebAssembly::SET_LOCAL_I64) &&
+          MI.getOperand(0).getImm() == MMIW.getStackPointerGlobal()) {
+        StackPointer = true;
       }
     }
   } else if (MI.hasOrderedMemoryRef()) {