Always append a job # to a --save-temps file if there are more than one task.

[ruiu]

Summary

It is a bit nitpicking, but I think the new naming scheme is what the
people would expect. For example, if we have three tasks,

foo0.lto.o
foo1.lto.o
foo2.lto.o

is more natural than

foo.lto.o
foo1.lto.o
foo2.lto.o

(But do we need this logic in the first place? I thought that we could
just always append a job number even when there's only one job.)

[pcc]

Seems reasonable to always append the number, I think we do the same thing for the other full-LTO temporaries (see http://llvm-cs.pcc.me.uk/lib/LTO/LTOBackend.cpp#81).

lld/ELF/LTO.cpp

std::vector<InputFile *> BitcodeCompiler::compile() {
 
   if (!Config->ThinLTOCacheDir.empty())
     pruneCache(Config->ThinLTOCacheDir, Config->ThinLTOCachePolicy);
 
   for (unsigned I = 0; I != MaxTasks; ++I) {
     if (Buff[I].empty())
       continue;
     if (Config->SaveTemps) {
-      if (I == 0)
+      if (MaxTasks == 1)
         saveBuffer(Buff[I], Config->OutputFile + ".lto.o");
       else
         saveBuffer(Buff[I], Config->OutputFile + Twine(I) + ".lto.o");
     }
     InputFile *Obj = createObjectFile(MemoryBufferRef(Buff[I], "lto.tmp"));
     Ret.push_back(Obj);
   }
 

lld/test/ELF/lto/parallel-internalize.ll

 ; REQUIRES: x86
 ; RUN: llvm-as -o %t.bc %s
 ; RUN: rm -f %t.lto.o %t1.lto.o
 ; RUN: ld.lld -m elf_x86_64 --lto-partitions=2 -save-temps -o %t %t.bc \
 ; RUN:   -e foo --lto-O0
 ; RUN: llvm-readobj -t -dyn-symbols %t | FileCheck %s
-; RUN: llvm-nm %t.lto.o | FileCheck --check-prefix=CHECK0 %s
+; RUN: llvm-nm %t0.lto.o | FileCheck --check-prefix=CHECK0 %s
 ; RUN: llvm-nm %t1.lto.o | FileCheck --check-prefix=CHECK1 %s
 
 ; CHECK:      Symbols [
 ; CHECK-NEXT:   Symbol {
 ; CHECK-NEXT:     Name:  (0)
 ; CHECK-NEXT:     Value: 0x0
 ; CHECK-NEXT:     Size: 0
 ; CHECK-NEXT:     Binding: Local (0x0)

lld/test/ELF/lto/parallel.ll

 ; REQUIRES: x86
 ; RUN: llvm-as -o %t.bc %s
 ; RUN: rm -f %t.lto.o %t1.lto.o
 ; RUN: ld.lld -m elf_x86_64 --lto-partitions=2 -save-temps -o %t %t.bc -shared
-; RUN: llvm-nm %t.lto.o | FileCheck --check-prefix=CHECK0 %s
+; RUN: llvm-nm %t0.lto.o | FileCheck --check-prefix=CHECK0 %s
 ; RUN: llvm-nm %t1.lto.o | FileCheck --check-prefix=CHECK1 %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 ; CHECK0-NOT: bar
 ; CHECK0: T foo
 ; CHECK0-NOT: bar