DI: Require subprogram definitions to be distinct

As a follow-up to r246098, require `DISubprogram` definitions
(`isDefinition: true`) to be 'distinct'.  Specifically, add an assembler
check, a verifier check, and bitcode upgrading logic to combat testcase
bitrot after the `DIBuilder` change.

While working on the testcases, I realized that
test/Linker/subprogram-linkonce-weak-odr.ll isn't relevant anymore.  Its
purpose was to check for a corner case in PR22792 where two subprogram
definitions match exactly and share the same metadata node.  The new
verifier check, requiring that subprogram definitions are 'distinct',
precludes that possibility.

I updated almost all the IR with the following script:

    git grep -l -E -e '= !DISubprogram\(.* isDefinition: true' |
    grep -v test/Bitcode |
    xargs sed -i '' -e 's/= \(!DISubprogram(.*, isDefinition: true\)/= distinct \1/'

Likely some variant of would work for out-of-tree testcases.

llvm-svn: 246327
diff --git a/llvm/test/DebugInfo/inheritance.ll b/llvm/test/DebugInfo/inheritance.ll
index f8924dc..802c4f1 100644
--- a/llvm/test/DebugInfo/inheritance.ll
+++ b/llvm/test/DebugInfo/inheritance.ll
@@ -108,7 +108,7 @@
 !0 = !DILocalVariable(name: "tst", line: 13, scope: !1, file: !4, type: !8)
 !1 = distinct !DILexicalBlock(line: 0, column: 0, file: !44, scope: !2)
 !2 = distinct !DILexicalBlock(line: 0, column: 0, file: !44, scope: !3)
-!3 = !DISubprogram(name: "main", linkageName: "main", line: 11, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: false, scope: !4, type: !5)
+!3 = distinct !DISubprogram(name: "main", linkageName: "main", line: 11, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: false, scope: !4, type: !5)
 !4 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "4.2.1 (Based on Apple Inc. build 5658) (LLVM build)", isOptimized: true, emissionKind: 0, file: !44, enums: !45, retainedTypes: !45)
 !5 = !DISubroutineType(types: !6)
 !6 = !{!7}
@@ -130,7 +130,7 @@
 !22 = !DILocation(line: 13, scope: !1)
 !23 = !DILocation(line: 14, scope: !1)
 !24 = !DILocalVariable(name: "this", line: 13, arg: 1, scope: !25, file: !4, type: !26)
-!25 = !DISubprogram(name: "test1", linkageName: "_ZN5test1C1Ev", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: false, scope: !4, type: !15)
+!25 = distinct !DISubprogram(name: "test1", linkageName: "_ZN5test1C1Ev", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: false, scope: !4, type: !15)
 !26 = !DIDerivedType(tag: DW_TAG_const_type, size: 64, align: 64, flags: DIFlagArtificial, file: !4, baseType: !27)
 !27 = !DIDerivedType(tag: DW_TAG_pointer_type, size: 64, align: 64, file: !4, baseType: !8)
 !28 = !DILocation(line: 1, scope: !25)
@@ -138,13 +138,13 @@
 !30 = distinct !DILexicalBlock(line: 0, column: 0, file: !44, scope: !31)
 !31 = distinct !DILexicalBlock(line: 0, column: 0, file: !44, scope: !25)
 !32 = !DILocalVariable(name: "this", line: 4, arg: 1, scope: !33, file: !4, type: !26)
-!33 = !DISubprogram(name: "~test1", linkageName: "_ZN5test1D1Ev", line: 4, isLocal: false, isDefinition: true, virtuality: DW_VIRTUALITY_virtual, virtualIndex: 6, isOptimized: false, scope: !8, type: !15, containingType: !8)
+!33 = distinct !DISubprogram(name: "~test1", linkageName: "_ZN5test1D1Ev", line: 4, isLocal: false, isDefinition: true, virtuality: DW_VIRTUALITY_virtual, virtualIndex: 6, isOptimized: false, scope: !8, type: !15, containingType: !8)
 !34 = !DILocation(line: 4, scope: !33)
 !35 = !DILocation(line: 5, scope: !36)
 !36 = distinct !DILexicalBlock(line: 0, column: 0, file: !44, scope: !33)
 !37 = !DILocation(line: 6, scope: !36)
 !38 = !DILocalVariable(name: "this", line: 4, arg: 1, scope: !39, file: !4, type: !26)
-!39 = !DISubprogram(name: "~test1", linkageName: "_ZN5test1D0Ev", line: 4, isLocal: false, isDefinition: true, virtuality: DW_VIRTUALITY_virtual, virtualIndex: 6, isOptimized: false, scope: !8, type: !15, containingType: !8)
+!39 = distinct !DISubprogram(name: "~test1", linkageName: "_ZN5test1D0Ev", line: 4, isLocal: false, isDefinition: true, virtuality: DW_VIRTUALITY_virtual, virtualIndex: 6, isOptimized: false, scope: !8, type: !15, containingType: !8)
 !40 = !DILocation(line: 4, scope: !39)
 !41 = !DILocation(line: 5, scope: !42)
 !42 = distinct !DILexicalBlock(line: 0, column: 0, file: !44, scope: !39)