[llvm-commits] [llvm] r152197 - in /llvm/trunk: include/llvm/DerivedTypes.h lib/VMCore/Type.cpp

[Chandler Carruth]

For those following along, this also helped -O0 quite a bit too.

My perf runs show a 22% improvement in the 'clang -O0' time for the linked
bitcode of 177.mesa, and looking at the slowest to compile file that Bill
Wendling identified, 'get.c', I see a 20% improvement in the 'clang -O0'
time for that individual file as well.

On Tue, Mar 6, 2012 at 6:33 PM, Chandler Carruth <chandlerc at gmail.com>wrote:

> Author: chandlerc
> Date: Tue Mar  6 20:33:09 2012
> New Revision: 152197
>
> URL: http://llvm.org/viewvc/llvm-project?rev=152197&view=rev
> Log:
> Cache the sized-ness of struct types, once we reach the steady state of
> "is sized". This prevents every query to isSized() from recursing over
> every sub-type of a struct type. This could get *very* slow for
> extremely deep nesting of structs, as in 177.mesa.
>
> This change is a 45% speedup for 'opt -O2' of 177.mesa.linked.bc, and
> likely a significant speedup for other cases as well. It even impacts
> -O0 cases because so many part of the code try to check whether a type
> is sized.
>
> Thanks for the review from Nick Lewycky and Benjamin Kramer on IRC.
>
> Modified:
>    llvm/trunk/include/llvm/DerivedTypes.h
>    llvm/trunk/lib/VMCore/Type.cpp
>
> Modified: llvm/trunk/include/llvm/DerivedTypes.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/DerivedTypes.h?rev=152197&r1=152196&r2=152197&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/DerivedTypes.h (original)
> +++ llvm/trunk/include/llvm/DerivedTypes.h Tue Mar  6 20:33:09 2012
> @@ -195,9 +195,10 @@
>     // This is the contents of the SubClassData field.
>     SCDB_HasBody = 1,
>     SCDB_Packed = 2,
> -    SCDB_IsLiteral = 4
> +    SCDB_IsLiteral = 4,
> +    SCDB_IsSized = 8
>   };
> -
> +
>   /// SymbolTableEntry - For a named struct that actually has a name, this
> is a
>   /// pointer to the symbol table entry (maintained by LLVMContext) for the
>   /// struct.  This is null if the type is an literal struct or if it is
> @@ -248,6 +249,9 @@
>   /// isOpaque - Return true if this is a type with an identity that has
> no body
>   /// specified yet.  These prints as 'opaque' in .ll files.
>   bool isOpaque() const { return (getSubclassData() & SCDB_HasBody) == 0; }
> +
> +  /// isSized - Return true if this is a sized type.
> +  bool isSized() const;
>
>   /// hasName - Return true if this is a named struct that has a non-empty
> name.
>   bool hasName() const { return SymbolTableEntry != 0; }
>
> Modified: llvm/trunk/lib/VMCore/Type.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/Type.cpp?rev=152197&r1=152196&r2=152197&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/VMCore/Type.cpp (original)
> +++ llvm/trunk/lib/VMCore/Type.cpp Tue Mar  6 20:33:09 2012
> @@ -185,16 +185,7 @@
>   if (!this->isStructTy())
>     return false;
>
> -  // Opaque structs have no size.
> -  if (cast<StructType>(this)->isOpaque())
> -    return false;
> -
> -  // Okay, our struct is sized if all of the elements are.
> -  for (subtype_iterator I = subtype_begin(), E = subtype_end(); I != E;
> ++I)
> -    if (!(*I)->isSized())
> -      return false;
> -
> -  return true;
> +  return cast<StructType>(this)->isSized();
>  }
>
>
>  //===----------------------------------------------------------------------===//
> @@ -579,6 +570,26 @@
>   return llvm::StructType::create(Ctx, StructFields, Name);
>  }
>
> +bool StructType::isSized() const {
> +  if ((getSubclassData() & SCDB_IsSized) != 0)
> +    return true;
> +  if (isOpaque())
> +    return false;
> +
> +  // Okay, our struct is sized if all of the elements are, but if one of
> the
> +  // elements is opaque, the struct isn't sized *yet*, but may become
> sized in
> +  // the future, so just bail out without caching.
> +  for (element_iterator I = element_begin(), E = element_end(); I != E;
> ++I)
> +    if (!(*I)->isSized())
> +      return false;
> +
> +  // Here we cheat a bit and cast away const-ness. The goal is to memoize
> when
> +  // we find a sized type, as types can only move from opaque to sized,
> not the
> +  // other way.
> +  const_cast<StructType*>(this)->setSubclassData(
> +    getSubclassData() | SCDB_IsSized);
> +  return true;
> +}
>
>  StringRef StructType::getName() const {
>   assert(!isLiteral() && "Literal structs never have names");
>
>
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