[clang] 38cf112 - Allow applying attributes to subset of allowed subjects.

[Artem Belevich via cfe-commits]

Author: Artem Belevich
Date: 2021-04-12T09:33:33-07:00
New Revision: 38cf112a6bc8502ff8cce6ef524cf04c07f90f96

URL: https://github.com/llvm/llvm-project/commit/38cf112a6bc8502ff8cce6ef524cf04c07f90f96
DIFF: https://github.com/llvm/llvm-project/commit/38cf112a6bc8502ff8cce6ef524cf04c07f90f96.diff

LOG: Allow applying attributes to subset of allowed subjects.

Differential Revision: https://reviews.llvm.org/D100136

Added: 
    

Modified: 
    clang/lib/Sema/SemaAttr.cpp
    clang/test/Parser/pragma-attribute.cpp
    clang/test/Sema/pragma-attribute-strict-subjects.c

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaAttr.cpp b/clang/lib/Sema/SemaAttr.cpp
index 88c050b01e3f..67e553a3b259 100644
--- a/clang/lib/Sema/SemaAttr.cpp
+++ b/clang/lib/Sema/SemaAttr.cpp
@@ -875,12 +875,33 @@ void Sema::ActOnPragmaAttributeAttribute(
     }
     Rules.clear();
   } else {
-    for (const auto &Rule : StrictSubjectMatchRuleSet) {
-      if (Rules.erase(Rule.first)) {
+    // Each rule in Rules must be a strict subset of the attribute's
+    // SubjectMatch rules.  I.e. we're allowed to use
+    // `apply_to=variables(is_global)` on an attrubute with SubjectList<[Var]>,
+    // but should not allow `apply_to=variables` on an attribute which has
+    // `SubjectList<[GlobalVar]>`.
+    for (const auto &StrictRule : StrictSubjectMatchRuleSet) {
+      // First, check for exact match.
+      if (Rules.erase(StrictRule.first)) {
         // Add the rule to the set of attribute receivers only if it's supported
         // in the current language mode.
-        if (Rule.second)
-          SubjectMatchRules.push_back(Rule.first);
+        if (StrictRule.second)
+          SubjectMatchRules.push_back(StrictRule.first);
+      }
+    }
+    // Check remaining rules for subset matches.
+    auto RulesToCheck = Rules;
+    for (const auto &Rule : RulesToCheck) {
+      attr::SubjectMatchRule MatchRule = attr::SubjectMatchRule(Rule.first);
+      if (auto ParentRule = getParentAttrMatcherRule(MatchRule)) {
+        if (llvm::any_of(StrictSubjectMatchRuleSet,
+                         [ParentRule](const auto &StrictRule) {
+                           return StrictRule.first == *ParentRule &&
+                                  StrictRule.second; // IsEnabled
+                         })) {
+          SubjectMatchRules.push_back(MatchRule);
+          Rules.erase(MatchRule);
+        }
       }
     }
   }

diff  --git a/clang/test/Parser/pragma-attribute.cpp b/clang/test/Parser/pragma-attribute.cpp
index 9d28832a902e..4644bc18359e 100644
--- a/clang/test/Parser/pragma-attribute.cpp
+++ b/clang/test/Parser/pragma-attribute.cpp
@@ -195,3 +195,12 @@ _Pragma("clang attribute pop");
 #pragma clang attribute pop
 #pragma clang attribute push([[clang::uninitialized]], apply_to = any(variable(is_parameter), variable(unless(is_parameter)))) // expected-error {{attribute 'uninitialized' can't be applied to 'variable(is_parameter)', and 'variable(unless(is_parameter))'}}
 #pragma clang attribute pop
+// We're allowed to apply attributes to subsets of allowed subjects.
+#pragma clang attribute push([[clang::no_destroy]], apply_to = variable)
+#pragma clang attribute pop
+#pragma clang attribute push([[clang::no_destroy]], apply_to = variable(is_thread_local))
+#pragma clang attribute pop
+#pragma clang attribute push([[clang::no_destroy]], apply_to = variable(is_global))
+#pragma clang attribute pop
+#pragma clang attribute push([[clang::no_destroy]], apply_to = any(variable(is_parameter), variable(unless(is_parameter))))
+#pragma clang attribute pop

diff  --git a/clang/test/Sema/pragma-attribute-strict-subjects.c b/clang/test/Sema/pragma-attribute-strict-subjects.c
index 42e3e20e766a..4f37c271ce34 100644
--- a/clang/test/Sema/pragma-attribute-strict-subjects.c
+++ b/clang/test/Sema/pragma-attribute-strict-subjects.c
@@ -55,9 +55,9 @@
 // expected-error at -1 {{attribute 'abi_tag' can't be applied to 'enum'}}
 #pragma clang attribute pop
 
-#pragma clang attribute push (__attribute__((abi_tag("a"))), apply_to = any(enum_constant, function, record(unless(is_union)), variable, variable(is_parameter)))
+#pragma clang attribute push (__attribute__((abi_tag("a"))), apply_to = any(enum_constant, function, record(unless(is_union)), variable, variable(is_parameter), enum))
 // FIXME: comma in this diagnostic is wrong.
-// expected-error at -2 {{attribute 'abi_tag' can't be applied to 'enum_constant', and 'variable(is_parameter)'}}
+// expected-error at -2 {{attribute 'abi_tag' can't be applied to 'enum_constant', and 'enum'}}
 #pragma clang attribute pop
 
 #pragma clang attribute push (__attribute__((abi_tag("a"))), apply_to = any(function, record(unless(is_union)), enum))