Commit ff171acf authored by Derek Schuff's avatar Derek Schuff
Browse files

[WebAssembly] Track frame registers through VReg and local allocation 

This change has 2 components:

Target-independent: add a method getDwarfFrameBase to TargetFrameLowering. It
describes how the Dwarf frame base will be encoded.  That can be a register (the
default), the CFA (which replaces NVPTX-specific logic in DwarfCompileUnit), or
a DW_OP_WASM_location descriptr.

WebAssembly: Allow WebAssemblyFunctionInfo::getFrameRegister to return the
correct virtual register instead of FP32/SP32 after WebAssemblyReplacePhysRegs
has run.  Make WebAssemblyExplicitLocals store the local it allocates for the
frame register. Use this local information to implement getDwarfFrameBase

The result is that the DW_AT_frame_base attribute is correctly encoded for each
subprogram, and each param and local variable has a correct DW_AT_location that
uses DW_OP_fbreg to refer to the frame base.

This is a reland of rG3a05c3969c18 with fixes for the expensive-checks
and Windows builds

Differential Revision: https://reviews.llvm.org/D71681
parent ee2de955

lld/test/wasm/debuginfo.test

+5 −2
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ CHECK-NEXT: DW_AT_name ("hi.c") 
CHECK:   DW_TAG_subprogram

CHECK-NEXT:                DW_AT_low_pc

CHECK-NEXT:                DW_AT_high_pc

CHECK-NEXT:                DW_AT_frame_base

CHECK-NEXT:                DW_AT_name	("test")

CHECK-NEXT:                DW_AT_decl_file	("/Users/yury/llvmwasm{{(/|\\)}}hi.c")

CHECK-NEXT:                DW_AT_decl_line	(3)
@@ -27,6 +28,7 @@ CHECK-NEXT: DW_AT_decl_line (3) 
CHECK:   DW_TAG_subprogram

CHECK-NEXT:                DW_AT_low_pc

CHECK-NEXT:                DW_AT_high_pc

CHECK-NEXT:                DW_AT_frame_base

CHECK-NEXT:                DW_AT_name	("_start")

CHECK-NEXT:                DW_AT_decl_file	("/Users/yury/llvmwasm{{(/|\\)}}hi.c")

CHECK-NEXT:                DW_AT_decl_line	(7)
@@ -43,7 +45,7 @@ CHECK-NEXT: DW_AT_name ("hi_foo.c") 


CHECK:   DW_TAG_variable

CHECK-NEXT:                DW_AT_name	("y")

CHECK-NEXT:                DW_AT_type	(0x00000097 "int[2]")

CHECK-NEXT:                DW_AT_type	(0x000000a1 "int[2]")

CHECK-NEXT:                DW_AT_external	(true)

CHECK-NEXT:                DW_AT_decl_file	("{{.*}}hi_foo.c")

CHECK-NEXT:                DW_AT_decl_line	(1)
@@ -65,7 +67,7 @@ CHECK-NEXT: DW_AT_encoding (DW_ATE_unsigned) 


CHECK:   DW_TAG_variable

CHECK-NEXT:                DW_AT_name	("z")

CHECK-NEXT:                DW_AT_type	(0x00000097 "int[2]")

CHECK-NEXT:                DW_AT_type	(0x000000a1 "int[2]")

CHECK-NEXT:                DW_AT_external	(true)

CHECK-NEXT:                DW_AT_decl_file	("{{.*}}hi_foo.c")

CHECK-NEXT:                DW_AT_decl_line	(8)
@@ -74,6 +76,7 @@ CHECK-NEXT: DW_AT_location (DW_OP_addr 0x0) 
CHECK:   DW_TAG_subprogram

CHECK-NEXT:                DW_AT_low_pc	

CHECK-NEXT:                DW_AT_high_pc

CHECK-NEXT:                DW_AT_frame_base

CHECK-NEXT:                DW_AT_name	("foo")

CHECK-NEXT:                DW_AT_decl_file	("{{.*}}hi_foo.c")

CHECK-NEXT:                DW_AT_decl_line	(3)

llvm/include/llvm/CodeGen/TargetFrameLowering.h

+19 −0
Original line number Diff line number Diff line
@@ -52,6 +52,21 @@ public: 
    unsigned Reg;

    int Offset; // Offset relative to stack pointer on function entry.

  };



  struct DwarfFrameBase {

    // The frame base may be either a register (the default), the CFA,

    // or a WebAssembly-specific location description.

    enum FrameBaseKind { Register, CFA, WasmFrameBase } Kind;

    struct WasmFrameBase {

      unsigned Kind; // Wasm local, global, or value stack

      unsigned Index;

    };

    union {

      unsigned Reg;

      struct WasmFrameBase WasmLoc;

    } Location;

  };



private:

  StackDirection StackDir;

  Align StackAlignment;
@@ -401,6 +416,10 @@ public: 
  /// Return initial CFA register value i.e. the one valid at the beginning of

  /// the function (before any stack operations).

  virtual unsigned getInitialCFARegister(const MachineFunction &MF) const;



  /// Return the frame base information to be encoded in the DWARF subprogram

  /// debug info.

  virtual DwarfFrameBase getDwarfFrameBase(const MachineFunction &MF) const;

};



} // End llvm namespace

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

+24 −6
Original line number Diff line number Diff line
@@ -400,15 +400,33 @@ 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 TargetFrameLowering *TFI = Asm->MF->getSubtarget().getFrameLowering();

    TargetFrameLowering::DwarfFrameBase FrameBase =

        TFI->getDwarfFrameBase(*Asm->MF);

    switch (FrameBase.Kind) {

    case TargetFrameLowering::DwarfFrameBase::Register: {

      if (Register::isPhysicalRegister(FrameBase.Location.Reg)) {

        MachineLocation Location(FrameBase.Location.Reg);

        addAddress(*SPDie, dwarf::DW_AT_frame_base, Location);

      }

      break;

    }

    case TargetFrameLowering::DwarfFrameBase::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 {

      const TargetRegisterInfo *RI = Asm->MF->getSubtarget().getRegisterInfo();

      MachineLocation Location(RI->getFrameRegister(*Asm->MF));

      if (Register::isPhysicalRegister(Location.getReg()))

        addAddress(*SPDie, dwarf::DW_AT_frame_base, Location);

      break;

    }

    case TargetFrameLowering::DwarfFrameBase::WasmFrameBase: {

      DIELoc *Loc = new (DIEValueAllocator) DIELoc;

      DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);

      DIExpressionCursor Cursor({});

      DwarfExpr.addWasmLocation(FrameBase.Location.WasmLoc.Kind,

                                FrameBase.Location.WasmLoc.Index);

      DwarfExpr.addExpression(std::move(Cursor));

      addBlock(*SPDie, dwarf::DW_AT_frame_base, DwarfExpr.finalize());

      break;

    }

    }

  }

llvm/lib/CodeGen/TargetFrameLoweringImpl.cpp

+6 −0
Original line number Diff line number Diff line
@@ -154,3 +154,9 @@ unsigned TargetFrameLowering::getInitialCFARegister(const MachineFunction &MF) 
    const {

  llvm_unreachable("getInitialCFARegister() not implemented!");

}



TargetFrameLowering::DwarfFrameBase

TargetFrameLowering::getDwarfFrameBase(const MachineFunction &MF) const {

  const TargetRegisterInfo *RI = MF.getSubtarget().getRegisterInfo();

  return DwarfFrameBase{DwarfFrameBase::Register, {RI->getFrameRegister(MF)}};

}

llvm/lib/Target/NVPTX/NVPTXFrameLowering.cpp

+5 −0
Original line number Diff line number Diff line
@@ -83,3 +83,8 @@ MachineBasicBlock::iterator NVPTXFrameLowering::eliminateCallFramePseudoInstr( 
  // ADJCALLSTACKUP instructions.

  return MBB.erase(I);

}



TargetFrameLowering::DwarfFrameBase

NVPTXFrameLowering::getDwarfFrameBase(const MachineFunction &MF) const {

  return {DwarfFrameBase::CFA, {0}};

}