From 5f177620c3a5fe5626d55d0189a5fc7352e78ad6 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Wed, 30 Dec 2015 05:13:03 +0000
Subject: [PATCH] [MS ABI] Improve our mangling of pass_object_size

We didn't add the artificial pass_object_size arguments to the
backreference map which bloated the size of manglings which involved
pass_object_size with duplicate types.

This lets us go from:
?qux@PassObjectSize@@YAHQAHW4__pass_object_size1@__clang@@0W4__pass_object_size1@3@@Z

to:
?qux@PassObjectSize@@YAHQAHW4__pass_object_size1@__clang@@01@Z

llvm-svn: 256622
---
 clang/lib/AST/MicrosoftMangle.cpp   | 34 +++++++++++++++++++++++++----
 clang/test/CodeGenCXX/mangle-ms.cpp |  4 ++++
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index ba8ff2702793..87d088cc11aa 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -224,6 +224,9 @@ class MicrosoftCXXNameMangler {
   typedef llvm::DenseMap<void *, unsigned> ArgBackRefMap;
   ArgBackRefMap TypeBackReferences;
 
+  typedef std::set<int> PassObjectSizeArgsSet;
+  PassObjectSizeArgsSet PassObjectSizeArgs;
+
   ASTContext &getASTContext() const { return Context.getASTContext(); }
 
   // FIXME: If we add support for __ptr32/64 qualifiers, then we should push
@@ -293,6 +296,7 @@ private:
   void mangleObjCMethodName(const ObjCMethodDecl *MD);
 
   void mangleArgumentType(QualType T, SourceRange Range);
+  void manglePassObjectSizeArg(const PassObjectSizeAttr *POSA);
 
   // Declare manglers for every type class.
 #define ABSTRACT_TYPE(CLASS, PARENT)
@@ -1083,8 +1087,10 @@ void MicrosoftCXXNameMangler::mangleTemplateInstantiationName(
   // Templates have their own context for back references.
   ArgBackRefMap OuterArgsContext;
   BackRefVec OuterTemplateContext;
+  PassObjectSizeArgsSet OuterPassObjectSizeArgs;
   NameBackReferences.swap(OuterTemplateContext);
   TypeBackReferences.swap(OuterArgsContext);
+  PassObjectSizeArgs.swap(OuterPassObjectSizeArgs);
 
   mangleUnscopedTemplateName(TD);
   mangleTemplateArgs(TD, TemplateArgs);
@@ -1092,6 +1098,7 @@ void MicrosoftCXXNameMangler::mangleTemplateInstantiationName(
   // Restore the previous back reference contexts.
   NameBackReferences.swap(OuterTemplateContext);
   TypeBackReferences.swap(OuterArgsContext);
+  PassObjectSizeArgs.swap(OuterPassObjectSizeArgs);
 }
 
 void
@@ -1477,6 +1484,27 @@ void MicrosoftCXXNameMangler::mangleArgumentType(QualType T,
   }
 }
 
+void MicrosoftCXXNameMangler::manglePassObjectSizeArg(
+    const PassObjectSizeAttr *POSA) {
+  int Type = POSA->getType();
+
+  auto Iter = PassObjectSizeArgs.insert(Type).first;
+  void *TypePtr = (void *)&*Iter;
+  ArgBackRefMap::iterator Found = TypeBackReferences.find(TypePtr);
+
+  if (Found == TypeBackReferences.end()) {
+    mangleArtificalTagType(TTK_Enum, "__pass_object_size" + llvm::utostr(Type),
+                           {"__clang"});
+
+    if (TypeBackReferences.size() < 10) {
+      size_t Size = TypeBackReferences.size();
+      TypeBackReferences[TypePtr] = Size;
+    }
+  } else {
+    Out << Found->second;
+  }
+}
+
 void MicrosoftCXXNameMangler::mangleType(QualType T, SourceRange Range,
                                          QualifierMangleMode QMM) {
   // Don't use the canonical types.  MSVC includes things like 'const' on
@@ -1879,10 +1907,8 @@ void MicrosoftCXXNameMangler::mangleFunctionType(const FunctionType *T,
       // necessary to just cross our fingers and hope this type+namespace
       // combination doesn't conflict with anything?
       if (D)
-        if (auto *P = D->getParamDecl(I)->getAttr<PassObjectSizeAttr>())
-          mangleArtificalTagType(TTK_Enum, "__pass_object_size" +
-                                               llvm::utostr(P->getType()),
-                                 {"__clang"});
+        if (const auto *P = D->getParamDecl(I)->getAttr<PassObjectSizeAttr>())
+          manglePassObjectSizeArg(P);
     }
     // <builtin-type>      ::= Z  # ellipsis
     if (Proto->isVariadic())
diff --git a/clang/test/CodeGenCXX/mangle-ms.cpp b/clang/test/CodeGenCXX/mangle-ms.cpp
index d95f781f1204..c2a311423a9d 100644
--- a/clang/test/CodeGenCXX/mangle-ms.cpp
+++ b/clang/test/CodeGenCXX/mangle-ms.cpp
@@ -440,6 +440,10 @@ namespace PassObjectSize {
 int foo(int *const i __attribute__((pass_object_size(0)))) { return 0; }
 // CHECK-DAG: define i32 @"\01?bar@PassObjectSize@@YAHQAHW4__pass_object_size1@__clang@@@Z"
 int bar(int *const i __attribute__((pass_object_size(1)))) { return 0; }
+// CHECK-DAG: define i32 @"\01?qux@PassObjectSize@@YAHQAHW4__pass_object_size1@__clang@@0W4__pass_object_size0@3@@Z"
+int qux(int *const i __attribute__((pass_object_size(1))), int *const j __attribute__((pass_object_size(0)))) { return 0; }
+// CHECK-DAG: define i32 @"\01?zot@PassObjectSize@@YAHQAHW4__pass_object_size1@__clang@@01@Z"
+int zot(int *const i __attribute__((pass_object_size(1))), int *const j __attribute__((pass_object_size(1)))) { return 0; }
 }
 
 namespace Atomic {