[llvm] r238084 - AsmPrinter: Remove the vtable-entry from DIEValue

[Duncan P. N. Exon Smith]

> On 2015-May-26, at 14:01, David Blaikie <dblaikie at gmail.com> wrote:
> 
> 
> 
> On Fri, May 22, 2015 at 6:45 PM, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:
> Author: dexonsmith
> Date: Fri May 22 20:45:07 2015
> New Revision: 238084
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=238084&view=rev
> Log:
> AsmPrinter: Remove the vtable-entry from DIEValue
> 
> Remove all virtual functions from `DIEValue`, dropping the vtable
> pointer from its layout.  Instead, create "impl" functions on the
> subclasses, and use the `DIEValue::Type` to implement the dynamic
> dispatch.
> 
> This is necessary -- obviously not sufficient -- for passing `DIEValue`s
> around by value.  However, this change stands on its own: we make tons
> of these.  I measured a drop in memory usage from 888 MB down to 860 MB,
> or around 3.2%.
> 
> (I'm looking at `llc` memory usage on `verify-uselistorder.lto.opt.bc`;
> see r236629 for details.)
> 
> Modified:
>     llvm/trunk/include/llvm/CodeGen/DIE.h
>     llvm/trunk/lib/CodeGen/AsmPrinter/DIE.cpp
> 
> Modified: llvm/trunk/include/llvm/CodeGen/DIE.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/DIE.h?rev=238084&r1=238083&r2=238084&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/CodeGen/DIE.h (original)
> +++ llvm/trunk/include/llvm/CodeGen/DIE.h Fri May 22 20:45:07 2015
> @@ -200,8 +200,6 @@ public:
>  /// to DWARF attribute classes.
>  ///
>  class DIEValue {
> -  virtual void anchor();
> -
>  public:
>    enum Type {
>      isInteger,
> @@ -222,7 +220,7 @@ protected:
>    Type Ty;
> 
>    explicit DIEValue(Type T) : Ty(T) {}
> -  virtual ~DIEValue() {}
> +  ~DIEValue() {}
> 
> = default? (I suppose eventually this will go away, once there are no derived types and it's all passed around by value?)

Yup, it'll disappear.
> 
> 
> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DIE.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DIE.cpp?rev=238084&r1=238083&r2=238084&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/AsmPrinter/DIE.cpp (original)
> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DIE.cpp Fri May 22 20:45:07 2015
> @@ -191,9 +191,66 @@ void DIE::dump() {
>  }
>  #endif
> 
> -void DIEValue::anchor() { }
> +void DIEValue::EmitValue(const AsmPrinter *AP, dwarf::Form Form) const {
> +  switch (Ty) {
> +#define EMIT_VALUE_IMPL(Kind)                                                  \
> +  case is##Kind:                                                               \
> +    cast<DIE##Kind>(this)->EmitValueImpl(AP, Form);                            \
> +    break;
> +    EMIT_VALUE_IMPL(Integer)
> +    EMIT_VALUE_IMPL(String)
> +    EMIT_VALUE_IMPL(Expr)
> +    EMIT_VALUE_IMPL(Label)
> +    EMIT_VALUE_IMPL(Delta)
> +    EMIT_VALUE_IMPL(Entry)
> +    EMIT_VALUE_IMPL(TypeSignature)
> +    EMIT_VALUE_IMPL(Block)
> +    EMIT_VALUE_IMPL(Loc)
> +    EMIT_VALUE_IMPL(LocList)
> 
> Worth (now, or in the planned future) having a .def file for these so the list doesn't have to be repeated?

Yeah, I guess this was just laziness on my part; copy paste isn't
maintainable, but it's easy :/.  I'll fix that up once the other
DIEValue patches go in; I hope you don't mind the delay, but
those are awkward to rebase because of `DIEValue` moving in the
file.

>  
> +#undef EMIT_VALUE_IMPL
> +  }
> +}
> +
> +unsigned DIEValue::SizeOf(const AsmPrinter *AP, dwarf::Form Form) const {
> +  switch (Ty) {
> +#define SIZE_OF_IMPL(Kind)                                                     \
> +  case is##Kind:                                                               \
> +    return cast<DIE##Kind>(this)->SizeOfImpl(AP, Form);
> +    SIZE_OF_IMPL(Integer)
> +    SIZE_OF_IMPL(String)
> +    SIZE_OF_IMPL(Expr)
> +    SIZE_OF_IMPL(Label)
> +    SIZE_OF_IMPL(Delta)
> +    SIZE_OF_IMPL(Entry)
> +    SIZE_OF_IMPL(TypeSignature)
> +    SIZE_OF_IMPL(Block)
> +    SIZE_OF_IMPL(Loc)
> +    SIZE_OF_IMPL(LocList)
> +#undef SIZE_OF_IMPL
> +  }
> +}
> 
>  #ifndef NDEBUG
> +void DIEValue::print(raw_ostream &O) const {
> +  switch (Ty) {
> +#define PRINT_IMPL(Kind)                                                       \
> +  case is##Kind:                                                               \
> +    cast<DIE##Kind>(this)->printImpl(O);                                       \
> +    break;
> +    PRINT_IMPL(Integer)
> +    PRINT_IMPL(String)
> +    PRINT_IMPL(Expr)
> +    PRINT_IMPL(Label)
> +    PRINT_IMPL(Delta)
> +    PRINT_IMPL(Entry)
> +    PRINT_IMPL(TypeSignature)
> +    PRINT_IMPL(Block)
> +    PRINT_IMPL(Loc)
> +    PRINT_IMPL(LocList)
> +#undef PRINT_IMPL
> +  }
> +}