diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 54e2f361a9f141..4420f6a2c1c382 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -727,9 +727,17 @@ void CXXNameMangler::mangleFunctionEncodingBareType(const FunctionDecl *FD) {
       EnableIfAttr *EIA = dyn_cast<EnableIfAttr>(*I);
       if (!EIA)
         continue;
-      Out << 'X';
-      mangleExpression(EIA->getCond());
-      Out << 'E';
+      if (Context.getASTContext().getLangOpts().getClangABICompat() >
+          LangOptions::ClangABI::Ver11) {
+        mangleTemplateArgExpr(EIA->getCond());
+      } else {
+        // Prior to Clang 12, we hardcoded the X/E around enable-if's argument,
+        // even though <template-arg> should not include an X/E around
+        // <expr-primary>.
+        Out << 'X';
+        mangleExpression(EIA->getCond());
+        Out << 'E';
+      }
     }
     Out << 'E';
     FunctionTypeDepth.pop(Saved);
diff --git a/clang/test/CodeGen/enable_if.c b/clang/test/CodeGen/enable_if.c
index 14550b9e2db935..327a201cdeba16 100644
--- a/clang/test/CodeGen/enable_if.c
+++ b/clang/test/CodeGen/enable_if.c
@@ -31,22 +31,22 @@ void bar(int m) __attribute__((overloadable, enable_if(m > 0, "")));
 void bar(int m) __attribute__((overloadable, enable_if(1, "")));
 // CHECK-LABEL: define{{.*}} void @test2
 void test2() {
-  // CHECK: store void (i32)* @_Z3barUa9enable_ifIXLi1EEEi
+  // CHECK: store void (i32)* @_Z3barUa9enable_ifILi1EEi
   void (*p)(int) = bar;
-  // CHECK: store void (i32)* @_Z3barUa9enable_ifIXLi1EEEi
+  // CHECK: store void (i32)* @_Z3barUa9enable_ifILi1EEi
   void (*p2)(int) = &bar;
-  // CHECK: store void (i32)* @_Z3barUa9enable_ifIXLi1EEEi
+  // CHECK: store void (i32)* @_Z3barUa9enable_ifILi1EEi
   p = bar;
-  // CHECK: store void (i32)* @_Z3barUa9enable_ifIXLi1EEEi
+  // CHECK: store void (i32)* @_Z3barUa9enable_ifILi1EEi
   p = &bar;
 
-  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifIXLi1EEEi to i8*)
+  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifILi1EEi to i8*)
   void *vp1 = (void*)&bar;
-  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifIXLi1EEEi to i8*)
+  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifILi1EEi to i8*)
   void *vp2 = (void*)bar;
-  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifIXLi1EEEi to i8*)
+  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifILi1EEi to i8*)
   vp1 = (void*)&bar;
-  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifIXLi1EEEi to i8*)
+  // CHECK: store i8* bitcast (void (i32)* @_Z3barUa9enable_ifILi1EEi to i8*)
   vp1 = (void*)bar;
 }
 
@@ -54,13 +54,13 @@ void baz(int m) __attribute__((overloadable, enable_if(1, "")));
 void baz(int m) __attribute__((overloadable));
 // CHECK-LABEL: define{{.*}} void @test3
 void test3() {
-  // CHECK: store void (i32)* @_Z3bazUa9enable_ifIXLi1EEEi
+  // CHECK: store void (i32)* @_Z3bazUa9enable_ifILi1EEi
   void (*p)(int) = baz;
-  // CHECK: store void (i32)* @_Z3bazUa9enable_ifIXLi1EEEi
+  // CHECK: store void (i32)* @_Z3bazUa9enable_ifILi1EEi
   void (*p2)(int) = &baz;
-  // CHECK: store void (i32)* @_Z3bazUa9enable_ifIXLi1EEEi
+  // CHECK: store void (i32)* @_Z3bazUa9enable_ifILi1EEi
   p = baz;
-  // CHECK: store void (i32)* @_Z3bazUa9enable_ifIXLi1EEEi
+  // CHECK: store void (i32)* @_Z3bazUa9enable_ifILi1EEi
   p = &baz;
 }
 
@@ -71,13 +71,13 @@ void qux(int m) __attribute__((overloadable, enable_if(1, ""),
 void qux(int m) __attribute__((overloadable, enable_if(1, "")));
 // CHECK-LABEL: define{{.*}} void @test4
 void test4() {
-  // CHECK: store void (i32)* @_Z3quxUa9enable_ifIXLi1EEXLi1EEEi
+  // CHECK: store void (i32)* @_Z3quxUa9enable_ifILi1ELi1EEi
   void (*p)(int) = qux;
-  // CHECK: store void (i32)* @_Z3quxUa9enable_ifIXLi1EEXLi1EEEi
+  // CHECK: store void (i32)* @_Z3quxUa9enable_ifILi1ELi1EEi
   void (*p2)(int) = &qux;
-  // CHECK: store void (i32)* @_Z3quxUa9enable_ifIXLi1EEXLi1EEEi
+  // CHECK: store void (i32)* @_Z3quxUa9enable_ifILi1ELi1EEi
   p = qux;
-  // CHECK: store void (i32)* @_Z3quxUa9enable_ifIXLi1EEXLi1EEEi
+  // CHECK: store void (i32)* @_Z3quxUa9enable_ifILi1ELi1EEi
   p = &qux;
 }
 
@@ -90,6 +90,6 @@ void test5() {
   int foo(char *i __attribute__((pass_object_size(0))))
       __attribute__((enable_if(1, ""), overloadable));
 
-  // CHECK: call i32 @_Z3fooUa9enable_ifIXLi1EEEPcU17pass_object_size0
+  // CHECK: call i32 @_Z3fooUa9enable_ifILi1EEPcU17pass_object_size0
   foo((void*)0);
 }
diff --git a/clang/test/CodeGenCXX/clang-abi-compat.cpp b/clang/test/CodeGenCXX/clang-abi-compat.cpp
index caf06bd5f9f6ef..80311aa320fe58 100644
--- a/clang/test/CodeGenCXX/clang-abi-compat.cpp
+++ b/clang/test/CodeGenCXX/clang-abi-compat.cpp
@@ -130,4 +130,9 @@ template void test7<A>(A::Int<1>);
 template<int N> using matrix1xN = int __attribute__((matrix_type(1, N)));
 template<int N> void test8(matrix1xN<N> a) {}
 template void test8<2>(matrix1xN<2> a);
+
+// PRE12: @_ZN12expr_primary5test9EUa9enable_ifIXLi1EEEv
+// V12:   @_ZN12expr_primary5test9EUa9enable_ifILi1EEv
+void test9(void) __attribute__((enable_if(1, ""))) {}
+
 }
diff --git a/clang/test/CodeGenCXX/enable_if.cpp b/clang/test/CodeGenCXX/enable_if.cpp
index 4e7707aaeed9c7..70386b87fcee36 100644
--- a/clang/test/CodeGenCXX/enable_if.cpp
+++ b/clang/test/CodeGenCXX/enable_if.cpp
@@ -5,7 +5,7 @@ int test5(int);
 template <typename T>
 T test5(T) __attribute__((enable_if(1, "better than non-template")));
 
-// CHECK: @_Z5test5IiEUa9enable_ifIXLi1EEET_S0_
+// CHECK: @_Z5test5IiEUa9enable_ifILi1EET_S0_
 int (*Ptr)(int) = &test5;
 
 // Test itanium mangling for attribute enable_if