[PDB] Print the most redundant type record indices with /summary

[PDB] Print the most redundant type record indices with /summary

Summary:
I used this information to motivate splitting up the Intrinsic::ID enum
(5d986953c8b917bacfaa1f800fc1e242559f76be) and adding a key method to
clang::Sema (586f65d31f32ca6bc8cfdb8a4f61bee5057bf6c8) which saved a
fair amount of object file size.

Example output for clang.pdb:

  Top 10 types responsible for the most TPI input bytes:
         index     total bytes   count     size
        0x3890:      8,671,220 = 1,805 *  4,804
       0xE13BE:      5,634,720 =   252 * 22,360
       0x6874C:      5,181,600 =   408 * 12,700
        0x2A1F:      4,520,528 = 1,574 *  2,872
       0x64BFF:      4,024,020 =   469 *  8,580
        0x1123:      4,012,020 = 2,157 *  1,860
        0x6952:      3,753,792 =   912 *  4,116
        0xC16F:      3,630,888 =   633 *  5,736
        0x69DD:      3,601,160 =   985 *  3,656
        0x678D:      3,577,904 =   319 * 11,216

In this case, we can see that record 0x3890 is responsible for ~8MB of
total object file size for objects in clang.

The user can then use llvm-pdbutil to find out what the record is:

  $ llvm-pdbutil dump -types -type-index 0x3890
                       Types (TPI Stream)
  ============================================================
    Showing 1 records.
       0x3890 | LF_FIELDLIST [size = 4804]
                - LF_STMEMBER [name = `WORDTYPE_MAX`, type = 0x1001, attrs = public]
                - LF_MEMBER [name = `U`, Type = 0x37F0, offset = 0, attrs = private]
                - LF_MEMBER [name = `BitWidth`, Type = 0x0075 (unsigned), offset = 8, attrs = private]
                - LF_METHOD [name = `APInt`, # overloads = 8, overload list = 0x3805]
  ...

In this case, we can see that these are members of the APInt class,
which is emitted in 1805 object files.

The next largest type is ASTContext:

  $ llvm-pdbutil dump -types -type-index 0xE13BE bin/clang.pdb
      0xE13BE | LF_FIELDLIST [size = 22360]
                - LF_BCLASS
                  type = 0x653EA, offset = 0, attrs = public
                - LF_MEMBER [name = `Types`, Type = 0x653EB, offset = 8, attrs = private]
                - LF_MEMBER [name = `ExtQualNodes`, Type = 0x653EC, offset = 24, attrs = private]
                - LF_MEMBER [name = `ComplexTypes`, Type = 0x653ED, offset = 48, attrs = private]
                - LF_MEMBER [name = `PointerTypes`, Type = 0x653EE, offset = 72, attrs = private]
  ...

ASTContext only appears 252 times, but the list of members is long, and
must be repeated everywhere it is used.

This was the output before I split Intrinsic::ID:

  Top 10 types responsible for the most TPI input:
        0x686C:     69,823,920 = 1,070 * 65,256
        0x686D:     69,819,640 = 1,070 * 65,252
        0x686E:     69,819,640 = 1,070 * 65,252
        0x686B:     16,371,000 = 1,070 * 15,300
        ...

These records were all lists of intrinsic enums.

Reviewers: MaskRay, ruiu

Subscribers: mgrang, zturner, thakis, hans, akhuang, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71437