clang-tidy altera-id-dependent-backward-branch: print notes after warning

[yeputons-gh]

Summary

In Clang notes are typically printed after a corresponding warning, not before.
For example, all notes issued before the first warning are ignored.

Running clang-tidy --checks=-*,altera-id-dependent-backward-branch a.cpp on the following code:

long get_local_id(int);
void error() {
  int ThreadID = get_local_id(0);
  for (int i = 0; i < ThreadID; i++) {
  }
  for (int i = 0; i < ThreadID; i++) {
  }
}

results in two warnings and a single note in between.

[carlosgalvezp]

Thanks for the fix! Can you land the patch or would need that we do it for you? If so please provide Github name and email for attribution.

[yeputons-gh]

Hi, @carlosgalvezp ! I don't have any commit rights for the LLVM project, so I probably need help. My GitHub handle is yeputons (https://github.com/yeputons/), my email for attribution is [e-mail] (that's my first name, last name)

clang-tools-extra/clang-tidy/altera/IdDependentBackwardBranchCheck.cpp

if (IDCall) { // Conditional expression calls an ID function directly.
            "to ID function call and may cause performance degradation")
           << Type;
       return;
     }
     // Conditional expression has DeclRefExpr(s), check ID-dependency.
     IdDependencyRecord *IdDepVar = hasIdDepVar(CondExpr);
     IdDependencyRecord *IdDepField = hasIdDepField(CondExpr);
     if (IdDepVar) {
-      // Change one of these to a Note
-      diag(IdDepVar->Location, IdDepVar->Message, DiagnosticIDs::Note);
       diag(CondExpr->getBeginLoc(),
            "backward branch (%select{do|while|for}0 loop) is ID-dependent due "
            "to variable reference to %1 and may cause performance degradation")
           << Type << IdDepVar->VariableDeclaration;
+      diag(IdDepVar->Location, IdDepVar->Message, DiagnosticIDs::Note);
     } else if (IdDepField) {
-      diag(IdDepField->Location, IdDepField->Message, DiagnosticIDs::Note);
       diag(CondExpr->getBeginLoc(),
            "backward branch (%select{do|while|for}0 loop) is ID-dependent due "
            "to member reference to %1 and may cause performance degradation")
           << Type << IdDepField->FieldDeclaration;
+      diag(IdDepField->Location, IdDepField->Message, DiagnosticIDs::Note);
     }
   }
 }
 
 } // namespace clang::tidy::altera

clang-tools-extra/test/clang-tidy/checkers/altera/id-dependent-backward-branch.cpp

do {
     accumulator++;
   } while (j < get_local_id(0));
   // CHECK-NOTES: :[[@LINE-1]]:12: warning: backward branch (do loop) is ID-dependent due to ID function call and may cause performance degradation [altera-id-dependent-backward-branch]
 
   // ==== Assignments ====
   int ThreadID = get_local_id(0);
 
   while (j < ThreadID) {
-    // CHECK-NOTES: :[[@LINE-3]]:3: note: assignment of ID-dependent variable ThreadID
-    // CHECK-NOTES: :[[@LINE-2]]:10: warning: backward branch (while loop) is ID-dependent due to variable reference to 'ThreadID' and may cause performance degradation [altera-id-dependent-backward-branch]
+    // CHECK-NOTES: :[[@LINE-1]]:10: warning: backward branch (while loop) is ID-dependent due to variable reference to 'ThreadID' and may cause performance degradation [altera-id-dependent-backward-branch]
+    // CHECK-NOTES: :[[@LINE-4]]:3: note: assignment of ID-dependent variable ThreadID
     accumulator++;
   }
 
   ExampleStruct Example;
   Example.IDDepField = get_local_id(0);
 
   // ==== Inferred Assignments ====
   int ThreadID2 = ThreadID * get_local_size(0);
 
   int ThreadID3 = Example.IDDepField; // OK: not used in any loops
 
   ExampleStruct UnusedStruct = {
       ThreadID * 2 // OK: not used in any loops
   };
 
   for (int i = 0; i < ThreadID2; i++) {
-    // CHECK-NOTES: :[[@LINE-9]]:3: note: inferred assignment of ID-dependent value from ID-dependent variable ThreadID
-    // CHECK-NOTES: :[[@LINE-2]]:19: warning: backward branch (for loop) is ID-dependent due to variable reference to 'ThreadID2' and may cause performance degradation [altera-id-dependent-backward-branch]
+    // CHECK-NOTES: :[[@LINE-1]]:19: warning: backward branch (for loop) is ID-dependent due to variable reference to 'ThreadID2' and may cause performance degradation [altera-id-dependent-backward-branch]
+    // CHECK-NOTES: :[[@LINE-10]]:3: note: inferred assignment of ID-dependent value from ID-dependent variable ThreadID
     accumulator++;
   }
 
   do {
     accumulator++;
   } while (j < ThreadID);
-  // CHECK-NOTES: :[[@LINE-29]]:3: note: assignment of ID-dependent variable ThreadID
-  // CHECK-NOTES: :[[@LINE-2]]:12: warning: backward branch (do loop) is ID-dependent due to variable reference to 'ThreadID' and may cause performance degradation [altera-id-dependent-backward-branch]
+  // CHECK-NOTES: :[[@LINE-1]]:12: warning: backward branch (do loop) is ID-dependent due to variable reference to 'ThreadID' and may cause performance degradation [altera-id-dependent-backward-branch]
+  // CHECK-NOTES: :[[@LINE-30]]:3: note: assignment of ID-dependent variable ThreadID
 
   for (int i = 0; i < Example.IDDepField; i++) {
-    // CHECK-NOTES: :[[@LINE-24]]:3: note: assignment of ID-dependent field IDDepField
-    // CHECK-NOTES: :[[@LINE-2]]:19: warning: backward branch (for loop) is ID-dependent due to member reference to 'IDDepField' and may cause performance degradation [altera-id-dependent-backward-branch]
+    // CHECK-NOTES: :[[@LINE-1]]:19: warning: backward branch (for loop) is ID-dependent due to member reference to 'IDDepField' and may cause performance degradation [altera-id-dependent-backward-branch]
+    // CHECK-NOTES: :[[@LINE-25]]:3: note: assignment of ID-dependent field IDDepField
     accumulator++;
   }
 
   while (j < Example.IDDepField) {
-    // CHECK-NOTES: :[[@LINE-30]]:3: note: assignment of ID-dependent field IDDepField
-    // CHECK-NOTES: :[[@LINE-2]]:10: warning: backward branch (while loop) is ID-dependent due to member reference to 'IDDepField' and may cause performance degradation [altera-id-dependent-backward-branch]
+    // CHECK-NOTES: :[[@LINE-1]]:10: warning: backward branch (while loop) is ID-dependent due to member reference to 'IDDepField' and may cause performance degradation [altera-id-dependent-backward-branch]
+    // CHECK-NOTES: :[[@LINE-31]]:3: note: assignment of ID-dependent field IDDepField
     accumulator++;
   }
 
   do {
     accumulator++;
   } while (j < Example.IDDepField);
-  // CHECK-NOTES: :[[@LINE-38]]:3: note: assignment of ID-dependent field IDDepField
-  // CHECK-NOTES: :[[@LINE-2]]:12: warning: backward branch (do loop) is ID-dependent due to member reference to 'IDDepField' and may cause performance degradation [altera-id-dependent-backward-branch]
+  // CHECK-NOTES: :[[@LINE-1]]:12: warning: backward branch (do loop) is ID-dependent due to member reference to 'IDDepField' and may cause performance degradation [altera-id-dependent-backward-branch]
+  // CHECK-NOTES: :[[@LINE-39]]:3: note: assignment of ID-dependent field IDDepField
 }
 
 void success() {
   int accumulator = 0;
 
   for (int i = 0; i < 1000; i++) {
     if (i < get_local_id(0)) {
       accumulator++;
     }
   }
 }