[WIP] Record WebAssembly specific frame pointer.

Author: yurydelendik

llvm/include/llvm/CodeGen/TargetRegisterInfo.h

@@ -210,6 +210,18 @@ struct RegClassWeight {
   unsigned WeightLimit;
 };
 
+struct FrameBaseLocation {
+  enum LocationKind { Register, CFA, TargetIndex } Kind;
+  struct TargetIndexInfo {
+    unsigned Index;
+    signed Offset;
+  };
+  union {
+    unsigned Reg;
+    TargetIndexInfo TI;
+  };
+};
+
 /// TargetRegisterInfo base class - We assume that the target defines a static
 /// array of TargetRegisterDesc objects that represent all of the machine
 /// registers that the target has.  As such, we simply have to track a pointer
@@ -992,6 +1004,14 @@ class TargetRegisterInfo : public MCRegisterInfo {
   /// for values allocated in the current stack frame.
   virtual Register getFrameRegister(const MachineFunction &MF) const = 0;
 
+  virtual FrameBaseLocation
+  getFrameBaseLocation(const MachineFunction &MF) const {
+    FrameBaseLocation Loc;
+    Loc.Kind = FrameBaseLocation::Register;
+    Loc.Reg = getFrameRegister(MF);
+    return Loc;
+  }
+
   /// Mark a register and all its aliases as reserved in the given set.
   void markSuperRegs(BitVector &RegisterSet, unsigned Reg) const;
 

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -392,13 +392,24 @@ DIE &DwarfCompileUnit::updateSubprogramScopeDIE(const DISubprogram *SP) {
 
   // Only include DW_AT_frame_base in full debug info
   if (!includeMinimalInlineScopes()) {
-    if (Asm->MF->getTarget().getTargetTriple().isNVPTX()) {
+    const TargetRegisterInfo *RI = Asm->MF->getSubtarget().getRegisterInfo();
+    auto FBL = RI->getFrameBaseLocation(*Asm->MF);
+    if (FBL.Kind == FrameBaseLocation::CFA) {
       DIELoc *Loc = new (DIEValueAllocator) DIELoc;
       addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_call_frame_cfa);
       addBlock(*SPDie, dwarf::DW_AT_frame_base, Loc);
+    } else if (FBL.Kind == FrameBaseLocation::TargetIndex) {
+      if (FBL.TI.Offset >= 0) {
+        DIELoc *Loc = new (DIEValueAllocator) DIELoc;
+        DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
+        DIExpressionCursor Cursor({});
+        DwarfExpr.addTargetIndexLocation(FBL.TI.Index, FBL.TI.Offset);
+        DwarfExpr.addExpression(std::move(Cursor));
+        addBlock(*SPDie, dwarf::DW_AT_frame_base, DwarfExpr.finalize());
+      }
     } else {
-      const TargetRegisterInfo *RI = Asm->MF->getSubtarget().getRegisterInfo();
-      MachineLocation Location(RI->getFrameRegister(*Asm->MF));
+      assert(FBL.Kind == FrameBaseLocation::Register);
+      MachineLocation Location(FBL.Reg);
       if (RI->isPhysicalRegister(Location.getReg()))
         addAddress(*SPDie, dwarf::DW_AT_frame_base, Location);
     }

llvm/lib/Target/NVPTX/NVPTXRegisterInfo.h

@@ -44,6 +44,13 @@ class NVPTXRegisterInfo : public NVPTXGenRegisterInfo {
 
   Register getFrameRegister(const MachineFunction &MF) const override;
 
+  FrameBaseLocation
+  getFrameBaseLocation(const MachineFunction &MF) const override {
+    FrameBaseLocation Loc;
+    Loc.Kind = FrameBaseLocation::CFA;
+    return Loc;
+  }
+
   ManagedStringPool *getStrPool() const {
     return const_cast<ManagedStringPool *>(&ManagedStrPool);
   }

llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp

@@ -385,6 +385,13 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
     Changed = true;
   }
 
+  {
+    auto RL = Reg2Local.find(MFI.SPVReg);
+    if (RL != Reg2Local.end()) {
+      MFI.SPLocal = RL->second;
+    }
+  }
+
 #ifndef NDEBUG
   // Assert that all registers have been stackified at this point.
   for (const MachineBasicBlock &MBB : MF) {

llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h

@@ -60,7 +60,8 @@ class WebAssemblyFunctionInfo final : public MachineFunctionInfo {
   bool CFGStackified = false;
 
 public:
-  explicit WebAssemblyFunctionInfo(MachineFunction &MF) : MF(MF) {}
+  explicit WebAssemblyFunctionInfo(MachineFunction &MF)
+      : MF(MF), SPVReg(WebAssembly::NoRegister) {}
   ~WebAssemblyFunctionInfo() override;
   void initializeBaseYamlFields(const yaml::WebAssemblyFunctionInfo &YamlMFI);
 
@@ -129,6 +130,9 @@ class WebAssemblyFunctionInfo final : public MachineFunctionInfo {
 
   bool isCFGStackified() const { return CFGStackified; }
   void setCFGStackified(bool Value = true) { CFGStackified = Value; }
+
+  unsigned SPVReg;
+  unsigned SPLocal;
 };
 
 void computeLegalValueVTs(const Function &F, const TargetMachine &TM, Type *Ty,

llvm/lib/Target/WebAssembly/WebAssemblyRegisterInfo.cpp

@@ -140,6 +140,16 @@ WebAssemblyRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
   return Regs[TFI->hasFP(MF)][TT.isArch64Bit()];
 }
 
+FrameBaseLocation
+WebAssemblyRegisterInfo::getFrameBaseLocation(const MachineFunction &MF) const {
+  const WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
+  FrameBaseLocation Loc;
+  Loc.Kind = FrameBaseLocation::TargetIndex;
+  signed Local = MFI.SPVReg != WebAssembly::NoRegister ? MFI.SPLocal : -1;
+  Loc.TI = {0, Local};
+  return Loc;
+}
+
 const TargetRegisterClass *
 WebAssemblyRegisterInfo::getPointerRegClass(const MachineFunction &MF,
                                             unsigned Kind) const {

llvm/lib/Target/WebAssembly/WebAssemblyRegisterInfo.h

@@ -41,6 +41,9 @@ class WebAssemblyRegisterInfo final : public WebAssemblyGenRegisterInfo {
   // Debug information queries.
   Register getFrameRegister(const MachineFunction &MF) const override;
 
+  FrameBaseLocation
+  getFrameBaseLocation(const MachineFunction &MF) const override;
+
   const TargetRegisterClass *
   getPointerRegClass(const MachineFunction &MF,
                      unsigned Kind = 0) const override;

llvm/lib/Target/WebAssembly/WebAssemblyReplacePhysRegs.cpp

@@ -88,8 +88,14 @@ bool WebAssemblyReplacePhysRegs::runOnMachineFunction(MachineFunction &MF) {
     for (auto I = MRI.reg_begin(PReg), E = MRI.reg_end(); I != E;) {
       MachineOperand &MO = *I++;
       if (!MO.isImplicit()) {
-        if (VReg == WebAssembly::NoRegister)
+        if (VReg == WebAssembly::NoRegister) {
           VReg = MRI.createVirtualRegister(RC);
+          if (PReg == WebAssembly::SP32) {
+            WebAssemblyFunctionInfo &MFI =
+                *MF.getInfo<WebAssemblyFunctionInfo>();
+            MFI.SPVReg = VReg;
+          }
+        }
         MO.setReg(VReg);
         if (MO.getParent()->isDebugValue())
           MO.setIsDebug();