Itanium Mangling: In 'enable_if', omit X/E around <expr-primary>.

The Clang enable_if extension is mangled as an <extended-qualifier>,
which is supposed to contain <template-args>. However, we were
unconditionally emitting X/E around its arguments, neglecting the fact
that <expr-primary> should be emitted directly without the surrounding
X/E.

Differential Revision: https://reviews.llvm.org/D95488

1 files changed, 11 insertions, 3 deletions

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 54e2f36..4420f6a 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);