[llvm] r270449 - llvm-dwp: Add an abstraction for the DWP string pool

[Rafael Espíndola via llvm-commits]

On 23 May 2016 at 12:32, David Blaikie via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: dblaikie
> Date: Mon May 23 11:32:11 2016
> New Revision: 270449
>
> URL: http://llvm.org/viewvc/llvm-project?rev=270449&view=rev
> Log:
> llvm-dwp: Add an abstraction for the DWP string pool
>
> Also reference strings in the memory mapped file, reduces memory usage
> on a large test case by 18.5%.
>
> Added:
>     llvm/trunk/tools/llvm-dwp/DWPStringPool.h
> Modified:
>     llvm/trunk/tools/llvm-dwp/DWPError.h
>     llvm/trunk/tools/llvm-dwp/llvm-dwp.cpp
>
> Modified: llvm/trunk/tools/llvm-dwp/DWPError.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-dwp/DWPError.h?rev=270449&r1=270448&r2=270449&view=diff
> ==============================================================================
> --- llvm/trunk/tools/llvm-dwp/DWPError.h (original)
> +++ llvm/trunk/tools/llvm-dwp/DWPError.h Mon May 23 11:32:11 2016
> @@ -1,6 +1,10 @@
> +#ifndef TOOLS_LLVM_DWP_DWPERROR
> +#define TOOLS_LLVM_DWP_DWPERROR
> +
>  #include "llvm/Support/Error.h"
>  #include "llvm/Support/ErrorHandling.h"
>  #include <string>
> +
>  namespace llvm {
>  class DWPError : public ErrorInfo<DWPError> {
>  public:
> @@ -15,3 +19,5 @@ private:
>    std::string Info;
>  };
>  }
> +
> +#endif
>
> Added: llvm/trunk/tools/llvm-dwp/DWPStringPool.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/llvm-dwp/DWPStringPool.h?rev=270449&view=auto
> ==============================================================================
> --- llvm/trunk/tools/llvm-dwp/DWPStringPool.h (added)
> +++ llvm/trunk/tools/llvm-dwp/DWPStringPool.h Mon May 23 11:32:11 2016
> @@ -0,0 +1,54 @@
> +#ifndef TOOLS_LLVM_DWP_DWPSTRINGPOOL
> +#define TOOLS_LLVM_DWP_DWPSTRINGPOOL
> +
> +#include "llvm/ADT/DenseMap.h"
> +#include "llvm/MC/MCSection.h"
> +#include "llvm/MC/MCStreamer.h"
> +#include <cassert>
> +
> +class DWPStringPool {
> +
> +  struct CStrDenseMapInfo {
> +    static inline const char *getEmptyKey() {
> +      return reinterpret_cast<const char *>(~static_cast<uintptr_t>(0));
> +    }
> +    static inline const char *getTombstoneKey() {
> +      return reinterpret_cast<const char *>(~static_cast<uintptr_t>(1));
> +    }
> +    static unsigned getHashValue(const char *Val) {
> +      assert(Val != getEmptyKey() && "Cannot hash the empty key!");
> +      assert(Val != getTombstoneKey() && "Cannot hash the tombstone key!");
> +      return (unsigned)hash_value(StringRef(Val));
> +    }
> +    static bool isEqual(const char *LHS, const char *RHS) {
> +      if (RHS == getEmptyKey())
> +        return LHS == getEmptyKey();
> +      if (RHS == getTombstoneKey())
> +        return LHS == getTombstoneKey();
> +      return strcmp(LHS, RHS) == 0;
> +    }
> +  };
> +
> +  MCStreamer &Out;
> +  MCSection *Sec;
> +  DenseMap<const char *, uint32_t, CStrDenseMapInfo> Pool;
> +  uint32_t Offset = 0;

Can't you use a DenseMap of StringRef?

Cheers,
Rafael