Reduce amount of work ODR hashing does.

When a FunctionProtoType is in the original type in a DecayedType, the decayed
type is a PointerType which points back the original FunctionProtoType.  The
visitor for ODRHashing will attempt to process both Type's, doing double work.
By chaining together multiple DecayedType's and FunctionProtoType's, this would
result in 2^N Type's visited only N DecayedType's and N FunctionProtoType's
exsit.  Another bug where VisitDecayedType and VisitAdjustedType did
redundant work doubled the work at each level, giving 4^N Type's visited.  This
patch removed the double work and detects when a FunctionProtoType decays to
itself to only check the Type once.  This lowers the exponential runtime to
linear runtime.  Fixes https://bugs.llvm.org/show_bug.cgi?id=41625

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@359960 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/AST/ODRHash.cpp b/lib/AST/ODRHash.cpp
index 4f4ea67d32f1f6333e1468ee35bd61fbdd8b4a6c..9d484bd5de54982904bad4467e30237bd9e56d1b 100644 (file)
--- a/lib/AST/ODRHash.cpp
+++ b/lib/AST/ODRHash.cpp
@@ -703,14 +703,36 @@ public:
   void VisitType(const Type *T) {}
 
   void VisitAdjustedType(const AdjustedType *T) {
-    AddQualType(T->getOriginalType());
-    AddQualType(T->getAdjustedType());
+    QualType Original = T->getOriginalType();
+    QualType Adjusted = T->getAdjustedType();
+
+    // The original type and pointee type can be the same, as in the case of
+    // function pointers decaying to themselves.  Set a bool and only process
+    // the type once, to prevent doubling the work.
+    SplitQualType split = Adjusted.split();
+    if (auto Pointer = dyn_cast<PointerType>(split.Ty)) {
+      if (Pointer->getPointeeType() == Original) {
+        Hash.AddBoolean(true);
+        ID.AddInteger(split.Quals.getAsOpaqueValue());
+        AddQualType(Original);
+        VisitType(T);
+        return;
+      }
+    }
+
+    // The original type and pointee type are different, such as in the case
+    // of a array decaying to an element pointer.  Set a bool to false and
+    // process both types.
+    Hash.AddBoolean(false);
+    AddQualType(Original);
+    AddQualType(Adjusted);
+
     VisitType(T);
   }
 
   void VisitDecayedType(const DecayedType *T) {
-    AddQualType(T->getDecayedType());
-    AddQualType(T->getPointeeType());
+    // getDecayedType and getPointeeType are derived from getAdjustedType
+    // and don't need to be separately processed.
     VisitAdjustedType(T);
   }
 

diff --git a/test/Modules/odr_hash.cpp b/test/Modules/odr_hash.cpp
index e4c5ba6f82a8467880b0e380a969f0f0c0270cc4..f22a8b8f8a01951ebb4a56ec3db77b3cafc25c77 100644 (file)
--- a/test/Modules/odr_hash.cpp
+++ b/test/Modules/odr_hash.cpp
@@ -4587,6 +4587,43 @@ int num = bar();
 #endif
 }
 
+namespace FunctionProtoTypeDecay {
+#if defined(FIRST)
+struct S1 {
+  struct X {};
+  using Y = X(X());
+};
+#elif defined(SECOND)
+struct S1 {
+  struct X {};
+  using Y = X(X(X()));
+};
+#else
+S1 s1;
+// expected-error@first.h:* {{'FunctionProtoTypeDecay::S1::Y' from module 'FirstModule' is not present in definition of 'FunctionProtoTypeDecay::S1' in module 'SecondModule'}}
+// expected-note@second.h:* {{declaration of 'Y' does not match}}
+#endif
+
+#if defined(FIRST)
+struct S2 {
+  struct X {};
+  using Y =
+      X(X(X(X(X(X(X(X(X(X(X(X(X(X(X(X(
+      X(X(X(X(X(X(X(X(X(X(X(X(X(X(X(X(
+      X(X(X(X(X(X(X(X(X(X(X(X(X(X(X(X(
+      X(X(X(X(X(X(X(X(X(X(X(X(X(X(X(X(
+      ))))))))))))))))
+      ))))))))))))))))
+      ))))))))))))))))
+      ))))))))))))))));
+};
+#elif defined(SECOND)
+#else
+S2 s2;
+#endif
+
+}
+
 // Keep macros contained to one file.
 #ifdef FIRST
 #undef FIRST