From ad32fdb927a37dba26cb8b56f3a6b11667fe6584 Mon Sep 17 00:00:00 2001
From: Dan Gohman <sunfish@mozilla.com>
Date: Fri, 25 Apr 2014 15:51:06 -0700
Subject: Introduce an Emscripten C++ ABI.

Emscripten uses the Itanium C++ ABI for most things, except that it uses
ARM C++ ABI pointers to member functions, to avoid the overhead of aligning
functions.
---
 include/clang/Basic/TargetCXXABI.h |  8 ++++++++
 lib/AST/ASTContext.cpp             |  2 ++
 lib/Basic/Targets.cpp              |  5 +++++
 lib/CodeGen/CodeGenModule.cpp      |  1 +
 lib/CodeGen/ItaniumCXXABI.cpp      | 17 +++++++++++------
 5 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/include/clang/Basic/TargetCXXABI.h b/include/clang/Basic/TargetCXXABI.h
index c9d28f8774..29e4e47076 100644
--- a/include/clang/Basic/TargetCXXABI.h
+++ b/include/clang/Basic/TargetCXXABI.h
@@ -71,6 +71,10 @@ public:
     ///   - guard variables  are smaller.
     GenericAArch64,
 
+    /// Emscripten uses the Itanium C++, with the exception that it uses
+    /// ARM-style pointers to member functions.
+    Emscripten,
+
     /// The Microsoft ABI is the ABI used by Microsoft Visual Studio (and
     /// compatible compilers).
     ///
@@ -104,6 +108,7 @@ public:
     case GenericAArch64:
     case GenericItanium:
     case GenericARM:
+    case Emscripten:
     case iOS:
       return true;
 
@@ -119,6 +124,7 @@ public:
     case GenericAArch64:
     case GenericItanium:
     case GenericARM:
+    case Emscripten:
     case iOS:
       return false;
 
@@ -187,6 +193,7 @@ public:
 
     case GenericAArch64:
     case GenericItanium:
+    case Emscripten:
     case iOS:   // old iOS compilers did not follow this rule
     case Microsoft:
       return true;
@@ -233,6 +240,7 @@ public:
     case GenericItanium:
     case GenericAArch64:
     case GenericARM:
+    case Emscripten:
     case iOS:
       return UseTailPaddingUnlessPOD03;
 
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 176aec53a2..b77977f7fd 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -651,6 +651,7 @@ CXXABI *ASTContext::createCXXABI(const TargetInfo &T) {
   case TargetCXXABI::GenericARM:
   case TargetCXXABI::iOS:
     return CreateARMCXXABI(*this);
+  case TargetCXXABI::Emscripten:     // Same as Itanium at this level
   case TargetCXXABI::GenericAArch64: // Same as Itanium at this level
   case TargetCXXABI::GenericItanium:
     return CreateItaniumCXXABI(*this);
@@ -7940,6 +7941,7 @@ MangleContext *ASTContext::createMangleContext() {
   case TargetCXXABI::GenericAArch64:
   case TargetCXXABI::GenericItanium:
   case TargetCXXABI::GenericARM:
+  case TargetCXXABI::Emscripten:
   case TargetCXXABI::iOS:
     return createItaniumMangleContext(*this, getDiagnostics());
   case TargetCXXABI::Microsoft:
diff --git a/lib/Basic/Targets.cpp b/lib/Basic/Targets.cpp
index b56b42c798..93da96f897 100644
--- a/lib/Basic/Targets.cpp
+++ b/lib/Basic/Targets.cpp
@@ -270,6 +270,11 @@ public:
     // beneficial.
     this->UserLabelPrefix = "";
     this->MaxAtomicPromoteWidth = this->MaxAtomicInlineWidth = 32;
+
+    // Emscripten uses the Itanium ABI mostly, but it uses ARM-style pointers
+    // to member functions so that it can avoid having to align function
+    // addresses.
+    this->TheCXXABI.set(TargetCXXABI::Emscripten);
   }
 };
 
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index 0b03a3c4b6..15e4a50eaa 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -57,6 +57,7 @@ static CGCXXABI &createCXXABI(CodeGenModule &CGM) {
   switch (CGM.getTarget().getCXXABI().getKind()) {
   case TargetCXXABI::GenericAArch64:
   case TargetCXXABI::GenericARM:
+  case TargetCXXABI::Emscripten:
   case TargetCXXABI::iOS:
   case TargetCXXABI::GenericItanium:
     return *CreateItaniumCXXABI(CGM);
diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index 3767e4f278..1568284a7d 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -231,18 +231,23 @@ CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) {
     return new ItaniumCXXABI(CGM, /* UseARMMethodPtrABI = */ true,
                              /* UseARMGuardVarABI = */ true);
 
+  case TargetCXXABI::Emscripten:
+    // Use ARM-style method pointers so that generated code
+    // does not assume anything about the alignment of function
+    // pointers.
+    return new ItaniumCXXABI(CGM, /* UseARMMethodPtrABI = */ true,
+                             /* UseARMGuardVarABI = */ false);
+
   case TargetCXXABI::GenericItanium:
-    switch (CGM.getContext().getTargetInfo().getTriple().getArch()) {
-    case llvm::Triple::le32:
-    case llvm::Triple::asmjs:
-      // Use ARM-style method pointers so that generated code
+    if (CGM.getContext().getTargetInfo().getTriple().getArch()
+        == llvm::Triple::le32) {
+      // For PNaCl, use ARM-style method pointers so that PNaCl code
       // does not assume anything about the alignment of function
       // pointers.
       return new ItaniumCXXABI(CGM, /* UseARMMethodPtrABI = */ true,
                                /* UseARMGuardVarABI = */ false);
-    default:
-      return new ItaniumCXXABI(CGM);
     }
+    return new ItaniumCXXABI(CGM);
 
   case TargetCXXABI::Microsoft:
     llvm_unreachable("Microsoft ABI is not Itanium-based");
-- 
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