Deduplicate S_CONSTANTs in LLD.

[akhuang]

Summary

Deduplicate S_CONSTANTS when linking, if they have the same value.

[rnk]

lgtm, thanks!

lld/test/COFF/Inputs/pdb-global-constants-a.s

+  .text
+  .def   @feat.00;
+  .scl  3;
+  .type 0;
+  .endef
+  .globl  @feat.00
+.set @feat.00, 0
+  .file "t.cpp"
+  .def   main;
+  .scl  2;
+  .type 32;
+  .endef
+  .globl  main                    # -- Begin function main
+  .p2align  4, 0x90
+main:                                   # @main
+.Lfunc_begin0:
+  .cv_func_id 0
+  .cv_file  1 "C:\\src\\testing\\t.cpp" "D28AB0CC784E17E5DF9BBB49CB629C81" 1
+  .cv_loc 0 1 4 0                 # t.cpp:4:0
+.seh_proc main
+# %bb.0:                                # %entry
+  pushq %rax
+  .seh_stackalloc 8
+  .seh_endprologue
+  movl  $0, 4(%rsp)
+.Ltmp0:
+  movl  $83, %eax
+  popq  %rcx
+  retq
+.Ltmp1:
+.Lfunc_end0:
+  .seh_handlerdata
+  .text
+  .seh_endproc
+                                        # -- End function
+  .section  .debug$S,"dr"
+  .p2align  2
+  .long 4                       # Debug section magic
+  .long 241
+  .long .Ltmp3-.Ltmp2           # Subsection size
+.Ltmp2:
+  .short  .Ltmp5-.Ltmp4           # Record length
+.Ltmp4:
+  .short  4412                    # Record kind: S_COMPILE3
+  .long 1                       # Flags and language
+  .short  208                     # CPUType
+  .short  9                       # Frontend version
+  .short  0
+  .short  0
+  .short  0
+  .short  9000                    # Backend version
+  .short  0
+  .short  0
+  .short  0
+  .asciz  "clang version 9.0.0 (https://github.com/llvm/llvm-project.git ad522e17b285b1f2667163d52da5abf0968ec650)" # Null-terminated compiler version string
+  .p2align  2
+.Ltmp5:
+.Ltmp3:
+  .p2align  2
+  .long 241                     # Symbol subsection for main
+  .long .Ltmp7-.Ltmp6           # Subsection size
+.Ltmp6:
+  .short  .Ltmp9-.Ltmp8           # Record length
+.Ltmp8:
+  .short  4423                    # Record kind: S_GPROC32_ID
+  .long 0                       # PtrParent
+  .long 0                       # PtrEnd
+  .long 0                       # PtrNext
+  .long .Lfunc_end0-main        # Code size
+  .long 0                       # Offset after prologue
+  .long 0                       # Offset before epilogue
+  .long 4098                    # Function type index
+  .secrel32 main            # Function section relative address
+  .secidx main                    # Function section index
+  .byte 0                       # Flags
+  .asciz  "main"                  # Function name
+  .p2align  2
+.Ltmp9:
+  .short  .Ltmp11-.Ltmp10         # Record length
+.Ltmp10:
+  .short  4114                    # Record kind: S_FRAMEPROC
+  .long 8                       # FrameSize
+  .long 0                       # Padding
+  .long 0                       # Offset of padding
+  .long 0                       # Bytes of callee saved registers
+  .long 0                       # Exception handler offset
+  .short  0                       # Exception handler section
+  .long 81920                   # Flags (defines frame register)
+  .p2align  2
+.Ltmp11:
+  .short  2                       # Record length
+  .short  4431                    # Record kind: S_PROC_ID_END
+.Ltmp7:
+  .p2align  2
+  .cv_linetable 0, main, .Lfunc_end0
+  .long 241                     # Symbol subsection for globals
+  .long .Ltmp13-.Ltmp12         # Subsection size
+.Ltmp12:
+  .short  .Ltmp15-.Ltmp14         # Record length
+.Ltmp14:
+  .short  4359                    # Record kind: S_CONSTANT
+  .long 4099                    # Type
+  .byte 0x29, 0x00              # Value
+  .asciz  "Foo"                   # Name
+  .p2align  2
+.Ltmp15:
+  .short  .Ltmp17-.Ltmp16         # Record length
+.Ltmp16:
+  .short  4359                    # Record kind: S_CONSTANT
+  .long 4099                    # Type
+  .byte 0x2a, 0x00              # Value
+  .asciz  "Bar"                   # Name
+  .p2align  2
+.Ltmp17:
+.Ltmp13:
+  .p2align  2
+  .cv_filechecksums               # File index to string table offset subsection
+  .cv_stringtable                 # String table
+  .long 241
+  .long .Ltmp19-.Ltmp18         # Subsection size
+.Ltmp18:
+  .short  .Ltmp21-.Ltmp20         # Record length
+.Ltmp20:
+  .short  4428                    # Record kind: S_BUILDINFO
+  .long 4102                    # LF_BUILDINFO index
+  .p2align  2
+.Ltmp21:
+.Ltmp19:
+  .p2align  2
+  .section  .debug$T,"dr"
+  .p2align  2
+  .long 4                       # Debug section magic
+  # ArgList (0x1000) {
+  #   TypeLeafKind: LF_ARGLIST (0x1201)
+  #   NumArgs: 0
+  #   Arguments [
+  #   ]
+  # }
+  .byte 0x06, 0x00, 0x01, 0x12
+  .byte 0x00, 0x00, 0x00, 0x00
+  # Procedure (0x1001) {
+  #   TypeLeafKind: LF_PROCEDURE (0x1008)
+  #   ReturnType: int (0x74)
+  #   CallingConvention: NearC (0x0)
+  #   FunctionOptions [ (0x0)
+  #   ]
+  #   NumParameters: 0
+  #   ArgListType: () (0x1000)
+  # }
+  .byte 0x0e, 0x00, 0x08, 0x10
+  .byte 0x74, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x10, 0x00, 0x00
+  # FuncId (0x1002) {
+  #   TypeLeafKind: LF_FUNC_ID (0x1601)
+  #   ParentScope: 0x0
+  #   FunctionType: int () (0x1001)
+  #   Name: main
+  # }
+  .byte 0x12, 0x00, 0x01, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x01, 0x10, 0x00, 0x00
+  .byte 0x6d, 0x61, 0x69, 0x6e
+  .byte 0x00, 0xf3, 0xf2, 0xf1
+  # Modifier (0x1003) {
+  #   TypeLeafKind: LF_MODIFIER (0x1001)
+  #   ModifiedType: int (0x74)
+  #   Modifiers [ (0x1)
+  #     Const (0x1)
+  #   ]
+  # }
+  .byte 0x0a, 0x00, 0x01, 0x10
+  .byte 0x74, 0x00, 0x00, 0x00
+  .byte 0x01, 0x00, 0xf2, 0xf1
+  # StringId (0x1004) {
+  #   TypeLeafKind: LF_STRING_ID (0x1605)
+  #   Id: 0x0
+  #   StringData: C:\src\testing
+  # }
+  .byte 0x16, 0x00, 0x05, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x43, 0x3a, 0x5c, 0x73
+  .byte 0x72, 0x63, 0x5c, 0x74
+  .byte 0x65, 0x73, 0x74, 0x69
+  .byte 0x6e, 0x67, 0x00, 0xf1
+  # StringId (0x1005) {
+  #   TypeLeafKind: LF_STRING_ID (0x1605)
+  #   Id: 0x0
+  #   StringData: t.cpp
+  # }
+  .byte 0x0e, 0x00, 0x05, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x74, 0x2e, 0x63, 0x70
+  .byte 0x70, 0x00, 0xf2, 0xf1
+  # BuildInfo (0x1006) {
+  #   TypeLeafKind: LF_BUILDINFO (0x1603)
+  #   NumArgs: 5
+  #   Arguments [
+  #     ArgType: C:\src\testing (0x1004)
+  #     ArgType: 0x0
+  #     ArgType: t.cpp (0x1005)
+  #     ArgType: 0x0
+  #     ArgType: 0x0
+  #   ]
+  # }
+  .byte 0x1a, 0x00, 0x03, 0x16
+  .byte 0x05, 0x00, 0x04, 0x10
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x05, 0x10
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0xf2, 0xf1
+
+  .addrsig

lld/test/COFF/Inputs/pdb-global-constants-b.s

+  .text
+  .def   @feat.00;
+  .scl  3;
+  .type 0;
+  .endef
+  .globl  @feat.00
+.set @feat.00, 0
+  .file "t2.cpp"
+  .def   "?foobar@@YAHXZ";
+  .scl  2;
+  .type 32;
+  .endef
+  .globl  "?foobar@@YAHXZ"        # -- Begin function ?foobar@@YAHXZ
+  .p2align  4, 0x90
+"?foobar@@YAHXZ":                       # @"?foobar@@YAHXZ"
+.Lfunc_begin0:
+  .cv_func_id 0
+# %bb.0:                                # %entry
+  .cv_file  1 "C:\\src\\testing\\t2.cpp" "C9D7AF07363FDE8EC16D73EC30039C5B" 1
+  .cv_loc 0 1 5 0                 # t2.cpp:5:0
+  movl  $84, %eax
+  retq
+.Ltmp0:
+.Lfunc_end0:
+                                        # -- End function
+  .section  .debug$S,"dr"
+  .p2align  2
+  .long 4                       # Debug section magic
+  .long 241
+  .long .Ltmp2-.Ltmp1           # Subsection size
+.Ltmp1:
+  .short  .Ltmp4-.Ltmp3           # Record length
+.Ltmp3:
+  .short  4412                    # Record kind: S_COMPILE3
+  .long 1                       # Flags and language
+  .short  208                     # CPUType
+  .short  9                       # Frontend version
+  .short  0
+  .short  0
+  .short  0
+  .short  9000                    # Backend version
+  .short  0
+  .short  0
+  .short  0
+  .asciz  "clang version 9.0.0 (https://github.com/llvm/llvm-project.git ad522e17b285b1f2667163d52da5abf0968ec650)" # Null-terminated compiler version string
+  .p2align  2
+.Ltmp4:
+.Ltmp2:
+  .p2align  2
+  .long 241                     # Symbol subsection for foobar
+  .long .Ltmp6-.Ltmp5           # Subsection size
+.Ltmp5:
+  .short  .Ltmp8-.Ltmp7           # Record length
+.Ltmp7:
+  .short  4423                    # Record kind: S_GPROC32_ID
+  .long 0                       # PtrParent
+  .long 0                       # PtrEnd
+  .long 0                       # PtrNext
+  .long .Lfunc_end0-"?foobar@@YAHXZ" # Code size
+  .long 0                       # Offset after prologue
+  .long 0                       # Offset before epilogue
+  .long 4098                    # Function type index
+  .secrel32 "?foobar@@YAHXZ" # Function section relative address
+  .secidx "?foobar@@YAHXZ"        # Function section index
+  .byte 0                       # Flags
+  .asciz  "foobar"                # Function name
+  .p2align  2
+.Ltmp8:
+  .short  .Ltmp10-.Ltmp9          # Record length
+.Ltmp9:
+  .short  4114                    # Record kind: S_FRAMEPROC
+  .long 0                       # FrameSize
+  .long 0                       # Padding
+  .long 0                       # Offset of padding
+  .long 0                       # Bytes of callee saved registers
+  .long 0                       # Exception handler offset
+  .short  0                       # Exception handler section
+  .long 0                       # Flags (defines frame register)
+  .p2align  2
+.Ltmp10:
+  .short  2                       # Record length
+  .short  4431                    # Record kind: S_PROC_ID_END
+.Ltmp6:
+  .p2align  2
+  .cv_linetable 0, "?foobar@@YAHXZ", .Lfunc_end0
+  .long 241                     # Symbol subsection for globals
+  .long .Ltmp12-.Ltmp11         # Subsection size
+.Ltmp11:
+  .short  .Ltmp14-.Ltmp13         # Record length
+.Ltmp13:
+  .short  4359                    # Record kind: S_CONSTANT
+  .long 4099                    # Type
+  .byte 0x2a, 0x00              # Value
+  .asciz  "Foo"                   # Name
+  .p2align  2
+.Ltmp14:
+  .short  .Ltmp16-.Ltmp15         # Record length
+.Ltmp15:
+  .short  4359                    # Record kind: S_CONSTANT
+  .long 4099                    # Type
+  .byte 0x2a, 0x00              # Value
+  .asciz  "Bar"                   # Name
+  .p2align  2
+.Ltmp16:
+.Ltmp12:
+  .p2align  2
+  .cv_filechecksums               # File index to string table offset subsection
+  .cv_stringtable                 # String table
+  .long 241
+  .long .Ltmp18-.Ltmp17         # Subsection size
+.Ltmp17:
+  .short  .Ltmp20-.Ltmp19         # Record length
+.Ltmp19:
+  .short  4428                    # Record kind: S_BUILDINFO
+  .long 4102                    # LF_BUILDINFO index
+  .p2align  2
+.Ltmp20:
+.Ltmp18:
+  .p2align  2
+  .section  .debug$T,"dr"
+  .p2align  2
+  .long 4                       # Debug section magic
+  # ArgList (0x1000) {
+  #   TypeLeafKind: LF_ARGLIST (0x1201)
+  #   NumArgs: 0
+  #   Arguments [
+  #   ]
+  # }
+  .byte 0x06, 0x00, 0x01, 0x12
+  .byte 0x00, 0x00, 0x00, 0x00
+  # Procedure (0x1001) {
+  #   TypeLeafKind: LF_PROCEDURE (0x1008)
+  #   ReturnType: int (0x74)
+  #   CallingConvention: NearC (0x0)
+  #   FunctionOptions [ (0x0)
+  #   ]
+  #   NumParameters: 0
+  #   ArgListType: () (0x1000)
+  # }
+  .byte 0x0e, 0x00, 0x08, 0x10
+  .byte 0x74, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x10, 0x00, 0x00
+  # FuncId (0x1002) {
+  #   TypeLeafKind: LF_FUNC_ID (0x1601)
+  #   ParentScope: 0x0
+  #   FunctionType: int () (0x1001)
+  #   Name: foobar
+  # }
+  .byte 0x12, 0x00, 0x01, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x01, 0x10, 0x00, 0x00
+  .byte 0x66, 0x6f, 0x6f, 0x62
+  .byte 0x61, 0x72, 0x00, 0xf1
+  # Modifier (0x1003) {
+  #   TypeLeafKind: LF_MODIFIER (0x1001)
+  #   ModifiedType: int (0x74)
+  #   Modifiers [ (0x1)
+  #     Const (0x1)
+  #   ]
+  # }
+  .byte 0x0a, 0x00, 0x01, 0x10
+  .byte 0x74, 0x00, 0x00, 0x00
+  .byte 0x01, 0x00, 0xf2, 0xf1
+  # StringId (0x1004) {
+  #   TypeLeafKind: LF_STRING_ID (0x1605)
+  #   Id: 0x0
+  #   StringData: C:\src\testing
+  # }
+  .byte 0x16, 0x00, 0x05, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x43, 0x3a, 0x5c, 0x73
+  .byte 0x72, 0x63, 0x5c, 0x74
+  .byte 0x65, 0x73, 0x74, 0x69
+  .byte 0x6e, 0x67, 0x00, 0xf1
+  # StringId (0x1005) {
+  #   TypeLeafKind: LF_STRING_ID (0x1605)
+  #   Id: 0x0
+  #   StringData: t2.cpp
+  # }
+  .byte 0x0e, 0x00, 0x05, 0x16
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x74, 0x32, 0x2e, 0x63
+  .byte 0x70, 0x70, 0x00, 0xf1
+  # BuildInfo (0x1006) {
+  #   TypeLeafKind: LF_BUILDINFO (0x1603)
+  #   NumArgs: 5
+  #   Arguments [
+  #     ArgType: C:\src\testing (0x1004)
+  #     ArgType: 0x0
+  #     ArgType: t2.cpp (0x1005)
+  #     ArgType: 0x0
+  #     ArgType: 0x0
+  #   ]
+  # }
+  .byte 0x1a, 0x00, 0x03, 0x16
+  .byte 0x05, 0x00, 0x04, 0x10
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x05, 0x10
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0x00, 0x00
+  .byte 0x00, 0x00, 0xf2, 0xf1
+
+  .addrsig

lld/test/COFF/pdb-global-constants.test

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj %S/Inputs/pdb-global-constants-a.s -o %t-a.obj -triple x86_64-windows-msvc
+# RUN: llvm-mc -filetype=obj %S/Inputs/pdb-global-constants-b.s -o %t-b.obj -triple x86_64-windows-msvc
+# RUN: lld-link -entry:main -nodefaultlib %t-a.obj %t-b.obj -out:%t.exe -pdb:%t.pdb -debug
+# RUN: llvm-pdbutil dump -globals %t.pdb | FileCheck %s
+
+# Test that lld deduplicates S_CONSTANT records with the same name and value.
+#
+# Compiled from this C code, using
+# clang t.cpp -g -gcodeview -S
+#
+# %t-a.cpp:
+# const int Foo = 41;
+# const int Bar = 42;
+# int main() { return Foo + Bar; }
+#
+# %t-b.cpp:
+# const int Foo = 42;
+# const int Bar = 42;
+# int foobar() { return Foo + Bar; }
+
+CHECK:                       Global Symbols
+CHECK:           88 | S_CONSTANT [size = 16] `Bar`
+CHECK-NEXT:           type = 0x1002 (const int), value = 42
+CHECK-NEXT:      72 | S_CONSTANT [size = 16] `Foo`
+CHECK-NEXT:           type = 0x1002 (const int), value = 41
+CHECK-NEXT:     128 | S_CONSTANT [size = 16] `Foo`
+CHECK-NEXT:           type = 0x1002 (const int), value = 42

llvm/lib/DebugInfo/PDB/Native/GSIStreamBuilder.cpp

 #include <vector>
 
 using namespace llvm;
 using namespace llvm::msf;
 using namespace llvm::pdb;
 using namespace llvm::codeview;
 
 struct llvm::pdb::GSIHashStreamBuilder {
-  struct UdtDenseMapInfo {
+  struct SymbolDenseMapInfo {
     static inline CVSymbol getEmptyKey() {
       static CVSymbol Empty;
       return Empty;
     }
     static inline CVSymbol getTombstoneKey() {
       static CVSymbol Tombstone(
           DenseMapInfo<ArrayRef<uint8_t>>::getTombstoneKey());
       return Tombstone;
     }
     static unsigned getHashValue(const CVSymbol &Val) {
       return xxHash64(Val.RecordData);
     }
     static bool isEqual(const CVSymbol &LHS, const CVSymbol &RHS) {
       return LHS.RecordData == RHS.RecordData;
     }
   };
 
   std::vector<CVSymbol> Records;
   uint32_t StreamIndex;
-  llvm::DenseSet<CVSymbol, UdtDenseMapInfo> UdtHashes;
+  llvm::DenseSet<CVSymbol, SymbolDenseMapInfo> SymbolHashes;
   std::vector<PSHashRecord> HashRecords;
   std::array<support::ulittle32_t, (IPHR_HASH + 32) / 32> HashBitmap;
   std::vector<support::ulittle32_t> HashBuckets;
 
   uint32_t calculateSerializedLength() const;
   uint32_t calculateRecordByteSize() const;
   Error commit(BinaryStreamWriter &Writer);
   void finalizeBuckets(uint32_t RecordZeroOffset);
 
   template <typename T> void addSymbol(const T &Symbol, MSFBuilder &Msf) {
     T Copy(Symbol);
     addSymbol(SymbolSerializer::writeOneSymbol(Copy, Msf.getAllocator(),
                                                CodeViewContainer::Pdb));
   }
   void addSymbol(const CVSymbol &Symbol) {
-    if (Symbol.kind() == S_UDT) {
-      auto Iter = UdtHashes.insert(Symbol);
+    if (Symbol.kind() == S_UDT || Symbol.kind() == S_CONSTANT) {
+      auto Iter = SymbolHashes.insert(Symbol);
       if (!Iter.second)
         return;
     }
 
     Records.push_back(Symbol);
   }
 };