[MC] Change std::sort to llvm::sort in response to r327219

[mgrang]

Summary

r327219 added wrappers to std::sort which randomly shuffle the container before sorting.
This will help in uncovering non-determinism caused due to undefined sorting
order of objects having the same key.

To make use of that infrastructure we need to invoke llvm::sort instead of std::sort.

Note: This patch is one of a series of patches to replace *all* std::sort to llvm::sort.
Refer the comments section in D44363 for a list of all the required patches.

[mgrang]

Ping for reviews please.

[ruiu]

I'm not familiar with r327219, but if a decision to use randomized sort has been made, why don't you replace all occurrences of std::sort with llvm::sort in a single patch? I don't think that an author of each file don't have to understand this kind of change and approve individually.

[mgrang]

In D45138#1062213, @ruiu wrote:

I'm not familiar with r327219, but if a decision to use randomized sort has been made, why don't you replace all occurrences of std::sort with llvm::sort in a single patch? I don't think that an author of each file don't have to understand this kind of change and approve individually.

I had a patch to replace *all* occurrences of std::sort to llvm::sort https://reviews.llvm.org/D44363. However, the reviewers felt that the patch was getting too big and suggested splitting it into smaller patches target-wise, tablegen, MC, etc. Hence these separate patches.

[ruiu]

LGTM

lib/MC/MachObjectWriter.cpp

for (const MCSymbol &Symbol : Asm.symbols()) {
     } else {
       MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
       assert(MSD.SectionIndex && "Invalid section index!");
       LocalSymbolData.push_back(MSD);
     }
   }
 
   // External and undefined symbols are required to be in lexicographic order.
-  std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
-  std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
+  llvm::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
+  llvm::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
 
   // Set the symbol indices.
   Index = 0;
   for (auto *SymbolData :
        {&LocalSymbolData, &ExternalSymbolData, &UndefinedSymbolData})
     for (MachSymbolData &Entry : *SymbolData)
       Entry.Symbol->setIndex(Index++);
 

lib/MC/WinCOFFObjectWriter.cpp

 // Write the section header.
 void WinCOFFObjectWriter::writeSectionHeaders() {
   // Section numbers must be monotonically increasing in the section
   // header, but our Sections array is not sorted by section number,
   // so make a copy of Sections and sort it.
   std::vector<COFFSection *> Arr;
   for (auto &Section : Sections)
     Arr.push_back(Section.get());
-  std::sort(Arr.begin(), Arr.end(),
+  llvm::sort(Arr.begin(), Arr.end(),
              [](const COFFSection *A, const COFFSection *B) {
                return A->Number < B->Number;
              });
 
   for (auto &Section : Arr) {
     if (Section->Number == -1)
       continue;
 
     COFF::section &S = Section->Header;
     if (Section->Relocations.size() >= 0xffff)
       S.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;