[clang] [Clang] Improve subsumption. (PR #132849)

[Younan Zhang via cfe-commits]

================
@@ -0,0 +1,194 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
+
+namespace A {
+template <typename T>
+concept C = true;
+
+template <typename T>
+requires C<T> && C<T>
+void f() {}
+
+template <typename T>
+requires C<T> && true
+void f() {}
+
+template <>
+void f<int>();
+}
+
+namespace B {
+template <typename T>
+concept A = true;
+template <typename T>
+concept B = true;
+
+template <typename T>
+requires (A<T> && B<T>)
+constexpr int f() { return 0; }
+
+template <typename T>
+requires (A<T> || B<T>)
+constexpr int f() { return 1; }
+
+static_assert(f<int>() == 0);
+}
+
+namespace GH122581 {
+// Test that producing a Conjunctive Normal Form
+// does not blow up exponentially.
+// i.e, this should terminate reasonably quickly
+// within a small memory footprint
+template <typename T> concept C0 = true;
+template <typename T> concept C1 = true;
+template <typename T> concept C2 = true;
+template <typename T> concept C3 = true;
+template <typename T> concept C4 = true;
+
+template <typename T>
+concept majority5 =
+    (C0<T> && C1<T> && C2<T>) ||
+    (C0<T> && C1<T> && C3<T>) ||
+    (C0<T> && C1<T> && C4<T>) ||
+    (C0<T> && C2<T> && C3<T>) ||
+    (C0<T> && C2<T> && C4<T>) ||
+    (C0<T> && C3<T> && C4<T>) ||
+    (C1<T> && C2<T> && C3<T>) ||
+    (C1<T> && C2<T> && C4<T>) ||
+    (C1<T> && C3<T> && C4<T>) ||
+    (C2<T> && C3<T> && C4<T>);
+
+template <typename T>concept Y = C0<T> && majority5<T>;
+template <typename T>concept Z = Y<T> && C1<T>;
+
+constexpr int foo(majority5 auto x) { return 10; }
+constexpr int foo(Y auto y) { return 20; }
+constexpr int foo(Z auto y) { return 30; }
+static_assert(foo(0) == 30);
+}
+
+namespace WhateverThisIs {
+template <typename T> concept C0 = true;
+template <typename T> concept C1 = true;
+template <typename T> concept C2 = true;
+template <typename T> concept C3 = true;
+template <typename T> concept C4 = true;
+
+template <typename T>
+concept X =
+    (C0<T> || C1<T> || C2<T>) &&
+    (C0<T> || C1<T> || C3<T>) &&
+    (C0<T> || C1<T> || C4<T>) &&
+    (C0<T> || C2<T> || C3<T>) &&
+    (C0<T> || C2<T> || C4<T>) &&
+    (C0<T> || C3<T> || C4<T>) &&
+    (C1<T> || C2<T> || C3<T>) &&
+    (C1<T> || C2<T> || C4<T>) &&
+    (C1<T> || C3<T> || C4<T>) &&
+    (C2<T> || C3<T> || C4<T>);
+
+template <typename T>concept Y = C0<T> && X<T>;
+
+template <typename T>concept Z = Y<T> && C1<T>;
+
+constexpr int foo(X auto x) { return 10; }
+constexpr int foo(Y auto y) { return 20; }
+constexpr int foo(Z auto y) { return 30; }
+
+static_assert(foo(0) == 30);
+}
+
+namespace WAT{
+template<typename T>
+concept Z0 = true;
+
+template<typename T>
+concept Z1 = true;
+
+template<typename T>
+concept Z2 = true;
+
+template<typename T>
+concept Z3 = true;
+
+template<typename T>
+concept Z4 = true;
+
+template<typename T>
+concept Z5 = true;
+
+template<typename T>
+concept Z6 = true;
+
+template<typename T>
+concept Z7 = true;
+
+template<typename T>
+concept Z8 = true;
+
+template<typename T>
+concept Z9 = true;
+
+template <typename T>
+concept X =
----------------
zyn0217 wrote:

And with this patch, how long does it take to compile? I'm a bit concerned that if it runs for minutes, it might slow down our CI in the future.

https://github.com/llvm/llvm-project/pull/132849