[llvm] [DebugInfo] Make DISubprogram's hashing always produce the same result (PR #90770)

[Augusto Noronha via llvm-commits]

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@@ -1184,4 +1186,52 @@ TEST(MetadataTest, DbgVariableRecordConversionRoutines) {
   UseNewDbgInfoFormat = false;
 }
 
+// Test that the hashing function for DISubprograms produce the same result
+// after replacing the temporary scope.
+TEST(DIBuilder, HashingDISubprogram) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M = std::make_unique<Module>("MyModule", Ctx);
+  DIBuilder DIB(*M);
+
+  DIFile *F = DIB.createFile("main.c", "/");
+  DICompileUnit *CU =
+      DIB.createCompileUnit(dwarf::DW_LANG_C, F, "Test", false, "", 0);
+
+  llvm::TempDIType ForwardDeclaredType =
+      llvm::TempDIType(DIB.createReplaceableCompositeType(
+          llvm::dwarf::DW_TAG_structure_type, "MyType", CU, F, 0, 0, 8, 8, {},
+          "UniqueIdentifier"));
+
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augusto2112 wrote:

The type is required because I'm testing that replacing the subprogram's scope (in this case, the type) from the temporary type to the actual one should not change the hashing function's result.

The bug that I'm solving with this is that some DISubprograms inside a DenseSet would get duplicated when the set resized, because the hashing function was not consistent before and after replacing their scope from a temporary type with the actual type.

https://github.com/llvm/llvm-project/pull/90770