[PATCH] D143803: [clang][alias|ifunc]: Add a diagnostic for mangled names

[Dhruv Chawla via Phabricator via cfe-commits]

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When an alias or ifunc attribute refers to a function name that is
mangled, a diagnostic is emitted to suggest the mangled name as a
replacement for the given function name for every matching name in the
current TU.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D143803

Files:
  clang/include/clang/Basic/DiagnosticFrontendKinds.td
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/test/CodeGen/alias.cpp
  clang/test/CodeGen/attr-ifunc.cpp


Index: clang/test/CodeGen/attr-ifunc.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGen/attr-ifunc.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -triple x86_64-linux -fsyntax-only -verify -emit-llvm-only %s
+
+void *f1_ifunc(void) { return nullptr; }
+void f1(void) __attribute__((ifunc("f1_ifunc")));
+// expected-error at -1 {{ifunc must point to a defined function}}
+// expected-note at -2 {{exists as a mangled name}}
+
+void *f6_resolver_resolver(void) { return 0; }
+void *f6_resolver(void) __attribute__((ifunc("f6_resolver_resolver")));
+// expected-error at -1 {{ifunc must point to a defined function}}
+// expected-note at -2 {{exists as a mangled name}}
+void f6(void) __attribute__((ifunc("f6_resolver")));
+// expected-error at -1 {{ifunc must point to a defined function}}
+// expected-note at -2 {{exists as a mangled name}}
Index: clang/test/CodeGen/alias.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGen/alias.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -triple x86_64-linux -fsyntax-only -verify -emit-llvm-only %s
+
+void *f1_ifunc(void) { return nullptr; }
+void f1(void) __attribute__((alias("f1_ifunc")));
+// expected-error at -1 {{alias must point to a defined variable or function}}
+// expected-note at -2 {{exists as a mangled name}}
+
+void *f6_resolver_resolver(void) { return 0; }
+void *f6_resolver(void) __attribute__((alias("f6_resolver_resolver")));
+// expected-error at -1 {{alias must point to a defined variable or function}}
+// expected-note at -2 {{exists as a mangled name}}
+void f6(void) __attribute__((alias("f6_resolver")));
+// expected-error at -1 {{alias must point to a defined variable or function}}
+// expected-note at -2 {{exists as a mangled name}}
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -341,7 +341,8 @@
 static bool checkAliasedGlobal(DiagnosticsEngine &Diags,
                                SourceLocation Location, bool IsIFunc,
                                const llvm::GlobalValue *Alias,
-                               const llvm::GlobalValue *&GV) {
+                               const llvm::GlobalValue *&GV,
+                               const llvm::MapVector<GlobalDecl, StringRef> &MangledDeclNames) {
   GV = getAliasedGlobal(Alias);
   if (!GV) {
     Diags.Report(Location, diag::err_cyclic_alias) << IsIFunc;
@@ -350,6 +351,16 @@
 
   if (GV->isDeclaration()) {
     Diags.Report(Location, diag::err_alias_to_undefined) << IsIFunc << IsIFunc;
+    // Provide a note if the given function is not found and exists as a
+    // mangled name
+    for (const auto &[Decl, Name] : MangledDeclNames) {
+      if (const auto *ND = dyn_cast<NamedDecl>(Decl.getDecl())) {
+        if (ND->getName() == GV->getName()) {
+           Diags.Report(Location, diag::note_alias_requires_mangled_name)
+               << GV->getName() << Name;
+        }
+      }
+    }
     return false;
   }
 
@@ -390,7 +401,8 @@
     StringRef MangledName = getMangledName(GD);
     llvm::GlobalValue *Alias = GetGlobalValue(MangledName);
     const llvm::GlobalValue *GV = nullptr;
-    if (!checkAliasedGlobal(Diags, Location, IsIFunc, Alias, GV)) {
+    if (!checkAliasedGlobal(Diags, Location, IsIFunc, Alias, GV,
+                            MangledDeclNames)) {
       Error = true;
       continue;
     }
Index: clang/include/clang/Basic/DiagnosticFrontendKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticFrontendKinds.td
+++ clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -278,6 +278,8 @@
 def err_alias_to_undefined : Error<
   "%select{alias|ifunc}0 must point to a defined "
   "%select{variable or |}1function">;
+def note_alias_requires_mangled_name : Note<
+  "'%0' exists as a mangled name, did you mean to use '%1'?">;
 def warn_alias_to_weak_alias : Warning<
   "%select{alias|ifunc}2 will always resolve to %0 even if weak definition of "
   "%1 is overridden">,


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