[clang-tools-extra] [clang-tidy] Fix `altera-id-dependent-backward-branch` false positives (PR #200660)

[Zeyi Xu via cfe-commits]

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@@ -64,6 +95,31 @@ void error() {
     accumulator++;
   }
 
+  struct {
+    int FieldFromVar;
+    int FieldFromField;
+  } InferredField;
+  InferredField.FieldFromVar = ThreadID * 2;
+  while (j < InferredField.FieldFromVar) {
+    // CHECK-NOTES: :[[@LINE-1]]:10: warning: backward branch (while loop) is ID-dependent due to member reference to 'FieldFromVar' and may cause performance degradation [altera-id-dependent-backward-branch]
+    // CHECK-NOTES: :[[@LINE-6]]:5: note: inferred assignment of ID-dependent member from ID-dependent variable ThreadID
+    accumulator++;
+  }
+
+  InferredField.FieldFromField = Example.IDDepField;
+  while (j < InferredField.FieldFromField) {
+    // CHECK-NOTES: :[[@LINE-1]]:10: warning: backward branch (while loop) is ID-dependent due to member reference to 'FieldFromField' and may cause performance degradation [altera-id-dependent-backward-branch]
+    // CHECK-NOTES: :[[@LINE-12]]:5: note: inferred assignment of ID-dependent member from ID-dependent member IDDepField
----------------
zeyi2 wrote:

By reading at the diagnostic, IMO it should point to the assignment `InferredField.FieldFromField = Example.IDDepField;` instead of the struct definition.

Should the test expectation be updated to something like this?

`// CHECK-NOTES: :[[@LINE-3]]:3: note: inferred assignment of ID-dependent member from ID-dependent member IDDepField`

Please correct me if I get anything wrong.

https://github.com/llvm/llvm-project/pull/200660