[llvm][aarch64] Fix Arm64EC name mangling algorithm (#115567)

Arm64EC uses a special name mangling mode that adds `$$h` between the
symbol name and its type. In MSVC's name mangling `@` is used to
separate the name and type BUT it is also used for other purposes, such
as the separator between paths in a fully qualified name.

The original algorithm was quite fragile and made assumptions that
didn't hold true for all MSVC mangled symbols, so instead of trying to
improve this algorithm we are now using the demangler to indicate where
the insertion point should be (i.e., to parse the fully-qualified name
and return the current string offset).

Also fixed `isArm64ECMangledFunctionName` to search for `@$$h` since the
`$$h` must always be after a `@`.

Fixes #115231

diff --git a/llvm/include/llvm/Demangle/Demangle.h b/llvm/include/llvm/Demangle/Demangle.h
index fe129603c0785d4360f9103e04b8c078886ecca8..132e5088b551484c103ff11d75a6be36b348289a 100644 (file)
--- a/llvm/include/llvm/Demangle/Demangle.h
+++ b/llvm/include/llvm/Demangle/Demangle.h
@@ -10,6 +10,7 @@
 #define LLVM_DEMANGLE_DEMANGLE_H
 
 #include <cstddef>
+#include <optional>
 #include <string>
 #include <string_view>
 
@@ -54,6 +55,9 @@ enum MSDemangleFlags {
 char *microsoftDemangle(std::string_view mangled_name, size_t *n_read,
                         int *status, MSDemangleFlags Flags = MSDF_None);
 
+std::optional<size_t>
+getArm64ECInsertionPointInMangledName(std::string_view MangledName);
+
 // Demangles a Rust v0 mangled symbol.
 char *rustDemangle(std::string_view MangledName);
 

diff --git a/llvm/include/llvm/Demangle/MicrosoftDemangle.h b/llvm/include/llvm/Demangle/MicrosoftDemangle.h
index 6891185a28e57fda3401b122bef7df52182b9993..276efa7603690ecf6a666aed747599f210ef87fc 100644 (file)
--- a/llvm/include/llvm/Demangle/MicrosoftDemangle.h
+++ b/llvm/include/llvm/Demangle/MicrosoftDemangle.h
@@ -9,6 +9,7 @@
 #ifndef LLVM_DEMANGLE_MICROSOFTDEMANGLE_H
 #define LLVM_DEMANGLE_MICROSOFTDEMANGLE_H
 
+#include "llvm/Demangle/Demangle.h"
 #include "llvm/Demangle/MicrosoftDemangleNodes.h"
 
 #include <cassert>
@@ -141,6 +142,9 @@ enum class FunctionIdentifierCodeGroup { Basic, Under, DoubleUnder };
 // It has a set of functions to parse mangled symbols into Type instances.
 // It also has a set of functions to convert Type instances to strings.
 class Demangler {
+  friend std::optional<size_t>
+  llvm::getArm64ECInsertionPointInMangledName(std::string_view MangledName);
+
 public:
   Demangler() = default;
   virtual ~Demangler() = default;

diff --git a/llvm/include/llvm/IR/Mangler.h b/llvm/include/llvm/IR/Mangler.h
index f28ffc961b6db06de4d7cbfb6a0f48ec349e575e..33af40c5ae98dd6acaba42f39a77080f071e4098 100644 (file)
--- a/llvm/include/llvm/IR/Mangler.h
+++ b/llvm/include/llvm/IR/Mangler.h
@@ -56,6 +56,12 @@ void emitLinkerFlagsForUsedCOFF(raw_ostream &OS, const GlobalValue *GV,
 std::optional<std::string> getArm64ECMangledFunctionName(StringRef Name);
 std::optional<std::string> getArm64ECDemangledFunctionName(StringRef Name);
 
+/// Check if an ARM64EC function name is mangled.
+bool inline isArm64ECMangledFunctionName(StringRef Name) {
+  return Name[0] == '#' ||
+         (Name[0] == '?' && Name.find("@$$h") != StringRef::npos);
+}
+
 } // End llvm namespace
 
 #endif

diff --git a/llvm/lib/Demangle/MicrosoftDemangle.cpp b/llvm/lib/Demangle/MicrosoftDemangle.cpp
index c5835e8c2e989dbcea7b6a822961db6a60bcb0bb..d35902a333767829b549b4dae02ae4e99bc8050e 100644 (file)
--- a/llvm/lib/Demangle/MicrosoftDemangle.cpp
+++ b/llvm/lib/Demangle/MicrosoftDemangle.cpp
@@ -24,6 +24,7 @@
 #include <array>
 #include <cctype>
 #include <cstdio>
+#include <optional>
 #include <string_view>
 #include <tuple>
 
@@ -2424,6 +2425,24 @@ void Demangler::dumpBackReferences() {
     std::printf("\n");
 }
 
+std::optional<size_t>
+llvm::getArm64ECInsertionPointInMangledName(std::string_view MangledName) {
+  std::string_view ProcessedName{MangledName};
+
+  // We only support this for MSVC-style C++ symbols.
+  if (!consumeFront(ProcessedName, '?'))
+    return std::nullopt;
+
+  // The insertion point is just after the name of the symbol, so parse that to
+  // remove it from the processed name.
+  Demangler D;
+  D.demangleFullyQualifiedSymbolName(ProcessedName);
+  if (D.Error)
+    return std::nullopt;
+
+  return MangledName.length() - ProcessedName.length();
+}
+
 char *llvm::microsoftDemangle(std::string_view MangledName, size_t *NMangled,
                               int *Status, MSDemangleFlags Flags) {
   Demangler D;

diff --git a/llvm/lib/IR/Mangler.cpp b/llvm/lib/IR/Mangler.cpp
index e6c3ea9d5688312b7874a8febc5908409c0e2f5d..884739b3212c6167fbd4bb882751c88fda4ff665 100644 (file)
--- a/llvm/lib/IR/Mangler.cpp
+++ b/llvm/lib/IR/Mangler.cpp
@@ -14,6 +14,7 @@
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/Demangle/Demangle.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
@@ -291,30 +292,25 @@ void llvm::emitLinkerFlagsForUsedCOFF(raw_ostream &OS, const GlobalValue *GV,
 }
 
 std::optional<std::string> llvm::getArm64ECMangledFunctionName(StringRef Name) {
-  bool IsCppFn = Name[0] == '?';
-  if (IsCppFn && Name.contains("$$h"))
-    return std::nullopt;
-  if (!IsCppFn && Name[0] == '#')
+  if (Name[0] != '?') {
+    // For non-C++ symbols, prefix the name with "#" unless it's already
+    // mangled.
+    if (Name[0] == '#')
+      return std::nullopt;
+    return std::optional<std::string>(("#" + Name).str());
+  }
+
+  // If the name contains $$h, then it is already mangled.
+  if (Name.contains("$$h"))
     return std::nullopt;
 
-  StringRef Prefix = "$$h";
-  size_t InsertIdx = 0;
-  if (IsCppFn) {
-    InsertIdx = Name.find("@@");
-    size_t ThreeAtSignsIdx = Name.find("@@@");
-    if (InsertIdx != std::string::npos && InsertIdx != ThreeAtSignsIdx) {
-      InsertIdx += 2;
-    } else {
-      InsertIdx = Name.find("@");
-      if (InsertIdx != std::string::npos)
-        InsertIdx++;
-    }
-  } else {
-    Prefix = "#";
-  }
+  // Ask the demangler where we should insert "$$h".
+  auto InsertIdx = getArm64ECInsertionPointInMangledName(Name);
+  if (!InsertIdx)
+    return std::nullopt;
 
   return std::optional<std::string>(
-      (Name.substr(0, InsertIdx) + Prefix + Name.substr(InsertIdx)).str());
+      (Name.substr(0, *InsertIdx) + "$$h" + Name.substr(*InsertIdx)).str());
 }
 
 std::optional<std::string>

diff --git a/llvm/unittests/IR/ManglerTest.cpp b/llvm/unittests/IR/ManglerTest.cpp
index f2b78a1f9876946630c0d2a01d971ecef6ed1224..f8a3152564fd9ab550cd0549e284203b7af7a252 100644 (file)
--- a/llvm/unittests/IR/ManglerTest.cpp
+++ b/llvm/unittests/IR/ManglerTest.cpp
@@ -174,4 +174,81 @@ TEST(ManglerTest, GOFF) {
             "L#foo");
 }
 
+TEST(ManglerTest, Arm64EC) {
+  constexpr std::string_view Arm64ECNames[] = {
+      // Basic C name.
+      "#Foo",
+
+      // Basic C++ name.
+      "?foo@@$$hYAHXZ",
+
+      // Regression test: https://github.com/llvm/llvm-project/issues/115231
+      "?GetValue@?$Wrapper@UA@@@@$$hQEBAHXZ",
+
+      // Symbols from:
+      // ```
+      // namespace A::B::C::D {
+      // struct Base {
+      //   virtual int f() { return 0; }
+      // };
+      // }
+      // struct Derived : public A::B::C::D::Base {
+      //   virtual int f() override { return 1; }
+      // };
+      // A::B::C::D::Base* MakeObj() { return new Derived(); }
+      // ```
+      // void * __cdecl operator new(unsigned __int64)
+      "??2@$$hYAPEAX_K@Z",
+      // public: virtual int __cdecl A::B::C::D::Base::f(void)
+      "?f@Base@D@C@B@A@@$$hUEAAHXZ",
+      // public: __cdecl A::B::C::D::Base::Base(void)
+      "??0Base@D@C@B@A@@$$hQEAA@XZ",
+      // public: virtual int __cdecl Derived::f(void)
+      "?f@Derived@@$$hUEAAHXZ",
+      // public: __cdecl Derived::Derived(void)
+      "??0Derived@@$$hQEAA@XZ",
+      // struct A::B::C::D::Base * __cdecl MakeObj(void)
+      "?MakeObj@@$$hYAPEAUBase@D@C@B@A@@XZ",
+
+      // Symbols from:
+      // ```
+      // template <typename T> struct WW { struct Z{}; };
+      // template <typename X> struct Wrapper {
+      //   int GetValue(typename WW<X>::Z) const;
+      // };
+      // struct A { };
+      // template <typename X> int Wrapper<X>::GetValue(typename WW<X>::Z) const
+      // { return 3; }
+      // template class Wrapper<A>;
+      // ```
+      // public: int __cdecl Wrapper<struct A>::GetValue(struct WW<struct
+      // A>::Z)const
+      "?GetValue@?$Wrapper@UA@@@@$$hQEBAHUZ@?$WW@UA@@@@@Z",
+  };
+
+  for (const auto &Arm64ECName : Arm64ECNames) {
+    // Check that this is a mangled name.
+    EXPECT_TRUE(isArm64ECMangledFunctionName(Arm64ECName))
+        << "Test case: " << Arm64ECName;
+    // Refuse to mangle it again.
+    EXPECT_FALSE(getArm64ECMangledFunctionName(Arm64ECName).has_value())
+        << "Test case: " << Arm64ECName;
+
+    // Demangle.
+    auto Arm64Name = getArm64ECDemangledFunctionName(Arm64ECName);
+    EXPECT_TRUE(Arm64Name.has_value()) << "Test case: " << Arm64ECName;
+    // Check that it is not mangled.
+    EXPECT_FALSE(isArm64ECMangledFunctionName(Arm64Name.value()))
+        << "Test case: " << Arm64ECName;
+    // Refuse to demangle it again.
+    EXPECT_FALSE(getArm64ECDemangledFunctionName(Arm64Name.value()).has_value())
+        << "Test case: " << Arm64ECName;
+
+    // Round-trip.
+    auto RoundTripArm64ECName =
+        getArm64ECMangledFunctionName(Arm64Name.value());
+    EXPECT_EQ(RoundTripArm64ECName, Arm64ECName);
+  }
+}
+
 } // end anonymous namespace