[MC][ELF] Change SHT_LLVM_CALL_GRAPH_PROFILE relocations from SHT_RELA to SHT_REL

... even on targets preferring RELA. The section is only consumed by ld.lld
which can handle REL.

Follow-up to D104080 as I explained in the review. There are two advantages:

* The D104080 code only handles RELA, so arm/i386/mips32 etc may warn for -fprofile-use=/-fprofile-sample-use= usage.
* Decrease object file size for RELA targets

While here, change the relocation to relocate weights, instead of 0,1,2,3,..
I failed to catch the issue during review.

lib/MC/ELFObjectWriter.cpp

@@ -142,7 +142,7 @@ struct ELFWriter {
 
   // TargetObjectWriter wrappers.
   bool is64Bit() const;
-  bool hasRelocationAddend() const;
+  bool usesRela(const MCSectionELF &Sec) const;
 
   uint64_t align(unsigned Alignment);
 
@@ -392,8 +392,9 @@ bool ELFWriter::is64Bit() const {
   return OWriter.TargetObjectWriter->is64Bit();
 }
 
-bool ELFWriter::hasRelocationAddend() const {
-  return OWriter.hasRelocationAddend();
+bool ELFWriter::usesRela(const MCSectionELF &Sec) const {
+  return OWriter.hasRelocationAddend() &&
+         Sec.getType() != ELF::SHT_LLVM_CALL_GRAPH_PROFILE;
 }
 
 // Emit the ELF header.
@@ -785,11 +786,12 @@ MCSectionELF *ELFWriter::createRelocationSection(MCContext &Ctx,
     return nullptr;
 
   const StringRef SectionName = Sec.getName();
-  std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
+  bool Rela = usesRela(Sec);
+  std::string RelaSectionName = Rela ? ".rela" : ".rel";
   RelaSectionName += SectionName;
 
   unsigned EntrySize;
-  if (hasRelocationAddend())
+  if (Rela)
     EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
   else
     EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
@@ -799,8 +801,8 @@ MCSectionELF *ELFWriter::createRelocationSection(MCContext &Ctx,
     Flags = ELF::SHF_GROUP;
 
   MCSectionELF *RelaSection = Ctx.createELFRelSection(
-      RelaSectionName, hasRelocationAddend() ? ELF::SHT_RELA : ELF::SHT_REL,
-      Flags, EntrySize, Sec.getGroup(), &Sec);
+      RelaSectionName, Rela ? ELF::SHT_RELA : ELF::SHT_REL, Flags, EntrySize,
+      Sec.getGroup(), &Sec);
   RelaSection->setAlignment(is64Bit() ? Align(8) : Align(4));
   return RelaSection;
 }
@@ -925,6 +927,7 @@ void ELFWriter::writeRelocations(const MCAssembler &Asm,
   // Sort the relocation entries. MIPS needs this.
   OWriter.TargetObjectWriter->sortRelocs(Asm, Relocs);
 
+  const bool Rela = usesRela(Sec);
   for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
     const ELFRelocationEntry &Entry = Relocs[e - i - 1];
     unsigned Index = Entry.Symbol ? Entry.Symbol->getIndex() : 0;
@@ -943,7 +946,7 @@ void ELFWriter::writeRelocations(const MCAssembler &Asm,
         ERE64.setSymbolAndType(Index, Entry.Type);
         write(ERE64.r_info);
       }
-      if (hasRelocationAddend())
+      if (Rela)
         write(Entry.Addend);
     } else {
       write(uint32_t(Entry.Offset));
@@ -952,7 +955,7 @@ void ELFWriter::writeRelocations(const MCAssembler &Asm,
       ERE32.setSymbolAndType(Index, Entry.Type);
       write(ERE32.r_info);
 
-      if (hasRelocationAddend())
+      if (Rela)
         write(uint32_t(Entry.Addend));
 
       if (OWriter.TargetObjectWriter->getEMachine() == ELF::EM_MIPS) {

lib/MC/MCELFStreamer.cpp

@@ -513,9 +513,10 @@ void MCELFStreamer::finalizeCGProfile() {
   SwitchSection(CGProfile);
   uint64_t Offset = 0;
   for (MCAssembler::CGProfileEntry &E : Asm.CGProfile) {
-    finalizeCGProfileEntry(E.From, Offset++);
-    finalizeCGProfileEntry(E.To, Offset++);
+    finalizeCGProfileEntry(E.From, Offset);
+    finalizeCGProfileEntry(E.To, Offset);
     emitIntValue(E.Count, sizeof(uint64_t));
+    Offset += sizeof(uint64_t);
   }
   PopSection();
 }

test/MC/ELF/cgprofile.s

@@ -31,30 +31,26 @@ late3:
 # CHECK-NEXT:   0010: 14000000 00000000 2A000000 00000000
 # CHECK-NEXT: )
 
-# CHECK:      Name: .rela.llvm.call-graph-profile (28)
-# CHECK-NEXT: Type: SHT_RELA (0x4)
+# CHECK:      Name: .rel.llvm.call-graph-profile (28)
+# CHECK-NEXT: Type: SHT_REL (0x9)
 # CHECK-NEXT: Flags [ (0x0)
 # CHECK-NEXT: ]
 # CHECK-NEXT: Address: 0x0
 # CHECK-NEXT: Offset: 0x140
-# CHECK-NEXT: Size: 192
+# CHECK-NEXT: Size: 128
 # CHECK-NEXT: Link: 7
 # CHECK-NEXT: Info: 5
 # CHECK-NEXT: AddressAlignment: 8
-# CHECK-NEXT: EntrySize: 24
+# CHECK-NEXT: EntrySize: 16
 # CHECK-NEXT: SectionData (
 # CHECK-NEXT:   0000: 00000000 00000000 00000000 02000000
-# CHECK-NEXT:   0010: 00000000 00000000 01000000 00000000
-# CHECK-NEXT:   0020: 00000000 05000000 00000000 00000000
-# CHECK-NEXT:   0030: 02000000 00000000 00000000 07000000
-# CHECK-NEXT:   0040: 00000000 00000000 03000000 00000000
-# CHECK-NEXT:   0050: 00000000 02000000 00000000 00000000
-# CHECK-NEXT:   0060: 04000000 00000000 00000000 06000000
-# CHECK-NEXT:   0070: 00000000 00000000 05000000 00000000
-# CHECK-NEXT:   0080: 00000000 03000000 00000000 00000000
-# CHECK-NEXT:   0090: 06000000 00000000 00000000 01000000
-# CHECK-NEXT:   00A0: 00000000 00000000 07000000 00000000
-# CHECK-NEXT:   00B0: 00000000 05000000 00000000 00000000
+# CHECK-NEXT:   0010: 00000000 00000000 00000000 05000000
+# CHECK-NEXT:   0020: 08000000 00000000 00000000 07000000
+# CHECK-NEXT:   0030: 08000000 00000000 00000000 02000000
+# CHECK-NEXT:   0040: 10000000 00000000 00000000 06000000
+# CHECK-NEXT:   0050: 10000000 00000000 00000000 03000000
+# CHECK-NEXT:   0060: 18000000 00000000 00000000 01000000
+# CHECK-NEXT:   0070: 18000000 00000000 00000000 05000000
 # CHECK-NEXT: )
 
 # CHECK: Symbols [

test/tools/llvm-readobj/ELF/call-graph-profile.test

@@ -34,8 +34,8 @@ Sections:
       - Weight: 89
       - Weight: 98
     EntSize: [[ENTSIZE=<none>]]
-  - Name: .rela.llvm.call-graph-profile
-    Type: SHT_RELA
+  - Name: .rel.llvm.call-graph-profile
+    Type: SHT_REL
     Info: .llvm.call-graph-profile
     Relocations:
       - Symbol: foo
@@ -98,8 +98,8 @@ Sections:
       - Weight: 10
       - Weight: 20
       - Weight: 20
-  - Name: .rela.llvm.call-graph-profile
-    Type: SHT_RELA
+  - Name: .rel.llvm.call-graph-profile
+    Type: SHT_REL
     Info: .llvm.call-graph-profile
     Relocations:
       - Symbol: 1
@@ -186,8 +186,8 @@ Sections:
       - Weight: 89
       - Weight: 98
     EntSize: [[ENTSIZE=<none>]]
-  - Name: .rela.llvm.call-graph-profile
-    Type: SHT_RELA
+  - Name: .rel.llvm.call-graph-profile
+    Type: SHT_REL
     Info: .llvm.call-graph-profile
     Relocations:
       - Symbol: foo
@@ -213,7 +213,7 @@ Symbols:
 # RUN: llvm-readobj %t6.o --cg-profile 2>&1 | FileCheck %s -DFILE=%t6.o --check-prefix=LLVM-RELOC-WRONG-SIZE
 # RUN: llvm-readobj %t6.o --elf-cg-profile 2>&1 | FileCheck %s -DFILE=%t6.o --check-prefix=LLVM-RELOC-WRONG-SIZE
 
-# LLVM-RELOC-WRONG-SIZE:      warning: '[[FILE]]': unable to load relocations for SHT_LLVM_CALL_GRAPH_PROFILE section: section [index 2] has invalid sh_entsize: expected 24, but got 32
+# LLVM-RELOC-WRONG-SIZE:      warning: '[[FILE]]': unable to load relocations for SHT_LLVM_CALL_GRAPH_PROFILE section: section [index 2] has invalid sh_entsize: expected 16, but got 24
 # LLVM-RELOC-WRONG-SIZE-NEXT: CGProfile [
 # LLVM-RELOC-WRONG-SIZE-NEXT:  CGProfileEntry {
 # LLVM-RELOC-WRONG-SIZE-NEXT:    Weight: 89
@@ -236,8 +236,8 @@ Sections:
       - Weight: 89
       - Weight: 98
     EntSize: [[ENTSIZE=<none>]]
-  - Name: .rela.llvm.call-graph-profile
-    Type: SHT_RELA
+  - Name: .rel.llvm.call-graph-profile
+    Type: SHT_REL
     Info: .llvm.call-graph-profile
     Relocations:
       - Symbol: foo
@@ -251,7 +251,7 @@ Sections:
       - Offset: 0x3
         Symbol: foo
         Type:   R_X86_64_NONE
-    EntSize: 32
+    EntSize: 24
 Symbols:
   - Name: foo
   - Name: bar

test/tools/llvm-readobj/ELF/demangle.test

@@ -199,8 +199,8 @@ Sections:
     Link: .symtab
     EntSize: 8
     Content: "2000000000000000"
-  - Name: .rela.llvm.call-graph-profile
-    Type: SHT_RELA
+  - Name: .rel.llvm.call-graph-profile
+    Type: SHT_REL
     Info: .llvm.call-graph-profile
     Relocations:
       - Symbol: 1

tools/llvm-readobj/ELFDumper.cpp

@@ -6723,20 +6723,20 @@ template <class ELFT> void LLVMELFDumper<ELFT>::printCGProfile() {
       return;
     }
 
-    Elf_Rela_Range CGProfileRela;
+    Elf_Rel_Range CGProfileRel;
     bool UseReloc = (CGRelSection != nullptr);
     if (UseReloc) {
-      Expected<Elf_Rela_Range> CGProfileRelaOrError =
-          this->Obj.relas(*CGRelSection);
+      Expected<Elf_Rel_Range> CGProfileRelaOrError =
+          this->Obj.rels(*CGRelSection);
       if (!CGProfileRelaOrError) {
         this->reportUniqueWarning("unable to load relocations for "
                                   "SHT_LLVM_CALL_GRAPH_PROFILE section: " +
                                   toString(CGProfileRelaOrError.takeError()));
         UseReloc = false;
       } else
-        CGProfileRela = *CGProfileRelaOrError;
+        CGProfileRel = *CGProfileRelaOrError;
 
-      if (UseReloc && CGProfileRela.size() != (CGProfileOrErr->size() * 2)) {
+      if (UseReloc && CGProfileRel.size() != (CGProfileOrErr->size() * 2)) {
         this->reportUniqueWarning(
             "number of from/to pairs does not match number of frequencies");
         UseReloc = false;
@@ -6746,7 +6746,7 @@ template <class ELFT> void LLVMELFDumper<ELFT>::printCGProfile() {
           "relocation section for a call graph section doesn't exist");
 
     auto GetIndex = [&](uint32_t Index) {
-      const Elf_Rel_Impl<ELFT, true> &Rel = CGProfileRela[Index];
+      const Elf_Rel_Impl<ELFT, false> &Rel = CGProfileRel[Index];
       return Rel.getSymbol(this->Obj.isMips64EL());
     };