Restore "[ThinLTO] Emit individual index files for distributed backends"

This restores commit r268627:
    Summary:
    When launching ThinLTO backends in a distributed build (currently
    supported in gold via the thinlto-index-only plugin option), emit
    an individual index file for each backend process as described here:
    http://lists.llvm.org/pipermail/llvm-dev/2016-April/098272.html

    ...

    Differential Revision: http://reviews.llvm.org/D19556

Address msan failures by avoiding std::prev on map.end(), the
theory is that this is causing issues due to some known UB problems
in __tree.

llvm-svn: 269059

3 files changed, 86 insertions, 1 deletions

diff --git a/llvm/test/ThinLTO/X86/Inputs/distributed_indexes.ll b/llvm/test/ThinLTO/X86/Inputs/distributed_indexes.ll
new file mode 100644
index 00000000000..4e0840f3691
--- /dev/null
+++ b/llvm/test/ThinLTO/X86/Inputs/distributed_indexes.ll
@@ -0,0 +1,4 @@
+define void @g() {
+entry:
+  ret void
+}
diff --git a/llvm/test/ThinLTO/X86/distributed_indexes.ll b/llvm/test/ThinLTO/X86/distributed_indexes.ll
new file mode 100644
index 00000000000..0700488b5e9
--- /dev/null
+++ b/llvm/test/ThinLTO/X86/distributed_indexes.ll
@@ -0,0 +1,47 @@
+; RUN: opt -module-summary %s -o %t1.bc
+; RUN: opt -module-summary %p/Inputs/distributed_indexes.ll -o %t2.bc
+; RUN: llvm-lto -thinlto-action=thinlink -o %t.index.bc %t1.bc %t2.bc
+; RUN: llvm-lto -thinlto-action=distributedindexes -thinlto-index %t.index.bc %t1.bc %t2.bc
+; RUN: llvm-bcanalyzer -dump %t1.bc.thinlto.bc | FileCheck %s --check-prefix=BACKEND1
+; RUN: llvm-bcanalyzer -dump %t2.bc.thinlto.bc | FileCheck %s --check-prefix=BACKEND2
+
+; The backend index for this module contains summaries from itself and
+; Inputs/distributed_indexes.ll, as it imports from the latter.
+; BACKEND1: <MODULE_STRTAB_BLOCK
+; BACKEND1-NEXT: <ENTRY {{.*}} record string = '{{.*}}distributed_indexes.ll.tmp{{.*}}.bc'
+; BACKEND1-NEXT: <ENTRY {{.*}} record string = '{{.*}}distributed_indexes.ll.tmp{{.*}}.bc'
+; BACKEND1-NEXT: </MODULE_STRTAB_BLOCK
+; BACKEND1-NEXT: <GLOBALVAL_SUMMARY_BLOCK
+; BACKEND1-NEXT: <VERSION
+; BACKEND1-NEXT: <COMBINED
+; BACKEND1-NEXT: <COMBINED
+; BACKEND1-NEXT: </GLOBALVAL_SUMMARY_BLOCK
+; BACKEND1-NEXT: <VALUE_SYMTAB
+; Check that the format is: op0=valueid, op1=offset, op2=funcguid,
+; where funcguid is the lower 64 bits of the function name MD5.
+; BACKEND1-NEXT: <COMBINED_ENTRY abbrevid={{[0-9]+}} op0={{1|2}} op1={{-3706093650706652785|-5300342847281564238}}
+; BACKEND1-NEXT: <COMBINED_ENTRY abbrevid={{[0-9]+}} op0={{1|2}} op1={{-3706093650706652785|-5300342847281564238}}
+; BACKEND1-NEXT: </VALUE_SYMTAB
+
+; The backend index for Input/distributed_indexes.ll contains summaries from
+; itself only, as it does not import anything.
+; BACKEND2: <MODULE_STRTAB_BLOCK
+; BACKEND2-NEXT: <ENTRY {{.*}} record string = '{{.*}}distributed_indexes.ll.tmp2.bc'
+; BACKEND2-NEXT: </MODULE_STRTAB_BLOCK
+; BACKEND2-NEXT: <GLOBALVAL_SUMMARY_BLOCK
+; BACKEND2-NEXT: <VERSION
+; BACKEND2-NEXT: <COMBINED
+; BACKEND2-NEXT: </GLOBALVAL_SUMMARY_BLOCK
+; BACKEND2-NEXT: <VALUE_SYMTAB
+; Check that the format is: op0=valueid, op1=offset, op2=funcguid,
+; where funcguid is the lower 64 bits of the function name MD5.
+; BACKEND2-NEXT: <COMBINED_ENTRY abbrevid={{[0-9]+}} op0=1 op1=-5300342847281564238
+; BACKEND2-NEXT: </VALUE_SYMTAB
+
+declare void @g(...)
+
+define void @f() {
+entry:
+  call void (...) @g()
+  ret void
+}
diff --git a/llvm/test/tools/gold/X86/thinlto.ll b/llvm/test/tools/gold/X86/thinlto.ll
index 4bf8aa68aa5..09bf21d4a82 100644
--- a/llvm/test/tools/gold/X86/thinlto.ll
+++ b/llvm/test/tools/gold/X86/thinlto.ll
@@ -21,7 +21,8 @@
 ; RUN:    --plugin-opt=thinlto \
 ; RUN:    --plugin-opt=thinlto-index-only \
 ; RUN:    -shared %t.o %t2.o -o %t3
-; RUN: llvm-bcanalyzer -dump %t3.thinlto.bc | FileCheck %s --check-prefix=COMBINED
+; RUN: llvm-bcanalyzer -dump %t.o.thinlto.bc | FileCheck %s --check-prefix=BACKEND1
+; RUN: llvm-bcanalyzer -dump %t2.o.thinlto.bc | FileCheck %s --check-prefix=BACKEND2
 ; RUN: not test -e %t3
 
 ; Ensure gold generates an index as well as a binary by default in ThinLTO mode.
@@ -53,6 +54,39 @@
 ; NM: T f
 ; NM2: T {{f|g}}
 
+; The backend index for this module contains summaries from itself and
+; Inputs/thinlto.ll, as it imports from the latter.
+; BACKEND1: <MODULE_STRTAB_BLOCK
+; BACKEND1-NEXT: <ENTRY {{.*}} record string = '{{.*}}/test/tools/gold/X86/Output/thinlto.ll.tmp{{.*}}.o'
+; BACKEND1-NEXT: <ENTRY {{.*}} record string = '{{.*}}/test/tools/gold/X86/Output/thinlto.ll.tmp{{.*}}.o'
+; BACKEND1-NEXT: </MODULE_STRTAB_BLOCK
+; BACKEND1-NEXT: <GLOBALVAL_SUMMARY_BLOCK
+; BACKEND1-NEXT: <VERSION
+; BACKEND1-NEXT: <COMBINED
+; BACKEND1-NEXT: <COMBINED
+; BACKEND1-NEXT: </GLOBALVAL_SUMMARY_BLOCK
+; BACKEND1-NEXT: <VALUE_SYMTAB
+; Check that the format is: op0=valueid, op1=offset, op2=funcguid,
+; where funcguid is the lower 64 bits of the function name MD5.
+; BACKEND1-NEXT: <COMBINED_ENTRY abbrevid={{[0-9]+}} op0={{1|2}} op1={{-3706093650706652785|-5300342847281564238}}
+; BACKEND1-NEXT: <COMBINED_ENTRY abbrevid={{[0-9]+}} op0={{1|2}} op1={{-3706093650706652785|-5300342847281564238}}
+; BACKEND1-NEXT: </VALUE_SYMTAB
+
+; The backend index for Input/thinlto.ll contains summaries from itself only,
+; as it does not import anything.
+; BACKEND2: <MODULE_STRTAB_BLOCK
+; BACKEND2-NEXT: <ENTRY {{.*}} record string = '{{.*}}/test/tools/gold/X86/Output/thinlto.ll.tmp2.o'
+; BACKEND2-NEXT: </MODULE_STRTAB_BLOCK
+; BACKEND2-NEXT: <GLOBALVAL_SUMMARY_BLOCK
+; BACKEND2-NEXT: <VERSION
+; BACKEND2-NEXT: <COMBINED
+; BACKEND2-NEXT: </GLOBALVAL_SUMMARY_BLOCK
+; BACKEND2-NEXT: <VALUE_SYMTAB
+; Check that the format is: op0=valueid, op1=offset, op2=funcguid,
+; where funcguid is the lower 64 bits of the function name MD5.
+; BACKEND2-NEXT: <COMBINED_ENTRY abbrevid={{[0-9]+}} op0=1 op1=-5300342847281564238
+; BACKEND2-NEXT: </VALUE_SYMTAB
+
 ; COMBINED: <MODULE_STRTAB_BLOCK
 ; COMBINED-NEXT: <ENTRY {{.*}} record string = '{{.*}}/test/tools/gold/X86/Output/thinlto.ll.tmp{{.*}}.o'
 ; COMBINED-NEXT: <ENTRY {{.*}} record string = '{{.*}}/test/tools/gold/X86/Output/thinlto.ll.tmp{{.*}}.o'