From 364355da26053c321180fa31ecd731d36c4cffae Mon Sep 17 00:00:00 2001
From: Dan Gohman <sunfish@mozilla.com>
Date: Fri, 25 Apr 2014 16:00:38 -0700
Subject: Don't align member functions.

Emscripten uses the ARM ABI for pointers to member functions and doesn't
require that member functions are aligned.
---
 include/clang/Basic/TargetCXXABI.h | 18 ++++++++++++++++++
 lib/CodeGen/CodeGenModule.cpp      |  8 +++++---
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/include/clang/Basic/TargetCXXABI.h b/include/clang/Basic/TargetCXXABI.h
index 29e4e47076..abdf899f5d 100644
--- a/include/clang/Basic/TargetCXXABI.h
+++ b/include/clang/Basic/TargetCXXABI.h
@@ -134,6 +134,24 @@ public:
     llvm_unreachable("bad ABI kind");
   }
 
+  /// \brief Are pointers to member functions differently aligned?
+  bool arePointersToMemberFunctionsAligned() const {
+    switch (getKind()) {
+    case Emscripten:
+    case GenericARM:
+    case GenericAArch64:
+      // ARM-style pointers to member functions put the discriminator in the
+      // this adjustment, so they don't require functions to have any special
+      // alignment.
+      return false;
+    case GenericItanium:
+    case iOS:
+    case Microsoft:
+      return true;
+    }
+    llvm_unreachable("bad ABI kind");
+  }
+
   /// \brief Is the default C++ member function calling convention
   /// the same as the default calling convention?
   bool isMemberFunctionCCDefault() const {
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index 15e4a50eaa..3fb7cba914 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -657,9 +657,11 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
   if (alignment)
     F->setAlignment(alignment);
 
-  // C++ ABI requires 2-byte alignment for member functions.
-  if (F->getAlignment() < 2 && isa<CXXMethodDecl>(D))
-    F->setAlignment(2);
+  if (getTarget().getCXXABI().arePointersToMemberFunctionsAligned()) {
+    // C++ ABI requires 2-byte alignment for member functions.
+    if (F->getAlignment() < 2 && isa<CXXMethodDecl>(D))
+      F->setAlignment(2);
+  }
 }
 
 void CodeGenModule::SetCommonAttributes(const Decl *D,
-- 
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