commit 7718695cc69524b2ccd578edd0acac8dfd847620
Author: Tim Northover <tnorthover@apple.com>
Date:   Thu Jun 6 16:00:40 2013 -0700

    Diagnose malformed x86 inline asm using 'y' constraint.
    
    X86's 'y' inline assembly constraint represents an MMX register, this change
    prevents Clang from hitting an assertion when passed an incompatible type to
    deal with.

diff --git a/lib/CodeGen/CGStmt.cpp b/lib/CodeGen/CGStmt.cpp
index 353d6c3..3e9b8d4 100644
--- a/lib/CodeGen/CGStmt.cpp
+++ b/lib/CodeGen/CGStmt.cpp
@@ -16,6 +16,7 @@
 #include "CodeGenModule.h"
 #include "TargetInfo.h"
 #include "clang/AST/StmtVisitor.h"
+#include "clang/Sema/SemaDiagnostic.h"
 #include "clang/Basic/PrettyStackTrace.h"
 #include "clang/Basic/TargetInfo.h"
 #include "llvm/ADT/StringExtras.h"
@@ -1559,10 +1560,15 @@ void CodeGenFunction::EmitAsmStmt(const AsmStmt &S) {
           ResultRegTypes.back() = ConvertType(InputTy);
         }
       }
-      if (llvm::Type* AdjTy = 
+      if (llvm::Type* AdjTy =
             getTargetHooks().adjustInlineAsmType(*this, OutputConstraint,
                                                  ResultRegTypes.back()))
         ResultRegTypes.back() = AdjTy;
+      else {
+        CGM.getDiags().Report(S.getAsmLoc(),
+                              diag::err_asm_invalid_type_in_input)
+            << OutExpr->getType() << OutputConstraint;
+      }
     } else {
       ArgTypes.push_back(Dest.getAddress()->getType());
       Args.push_back(Dest.getAddress());
@@ -1578,8 +1584,8 @@ void CodeGenFunction::EmitAsmStmt(const AsmStmt &S) {
                                             InOutConstraints);
 
       if (llvm::Type* AdjTy =
-            getTargetHooks().adjustInlineAsmType(*this, OutputConstraint,
-                                                 Arg->getType()))
+          getTargetHooks().adjustInlineAsmType(*this, OutputConstraint,
+                                               Arg->getType()))
         Arg = Builder.CreateBitCast(Arg, AdjTy);
 
       if (Info.allowsRegister())
@@ -1644,6 +1650,9 @@ void CodeGenFunction::EmitAsmStmt(const AsmStmt &S) {
               getTargetHooks().adjustInlineAsmType(*this, InputConstraint,
                                                    Arg->getType()))
       Arg = Builder.CreateBitCast(Arg, AdjTy);
+    else
+      CGM.getDiags().Report(S.getAsmLoc(), diag::err_asm_invalid_type_in_input)
+          << InputExpr->getType() << InputConstraint;
 
     ArgTypes.push_back(Arg->getType());
     Args.push_back(Arg);
diff --git a/lib/CodeGen/TargetInfo.cpp b/lib/CodeGen/TargetInfo.cpp
index c4ee724..6881ea7 100644
--- a/lib/CodeGen/TargetInfo.cpp
+++ b/lib/CodeGen/TargetInfo.cpp
@@ -503,8 +503,16 @@ bool IsX86_MMXType(llvm::Type *IRType) {
 static llvm::Type* X86AdjustInlineAsmType(CodeGen::CodeGenFunction &CGF,
                                           StringRef Constraint,
                                           llvm::Type* Ty) {
-  if ((Constraint == "y" || Constraint == "&y") && Ty->isVectorTy())
+  if ((Constraint == "y" || Constraint == "&y") && Ty->isVectorTy()) {
+    if (cast<llvm::VectorType>(Ty)->getBitWidth() != 64) {
+      // Invalid MMX constraint
+      return 0;
+    }
+
     return llvm::Type::getX86_MMXTy(CGF.getLLVMContext());
+  }
+
+  // No operation needed
   return Ty;
 }
 
diff --git a/lib/CodeGen/TargetInfo.h b/lib/CodeGen/TargetInfo.h
index b0ddebc..ab7b061 100644
--- a/lib/CodeGen/TargetInfo.h
+++ b/lib/CodeGen/TargetInfo.h
@@ -111,8 +111,13 @@ namespace clang {
       return Address;
     }
 
+    /// Corrects the low-level LLVM type for a given constraint and "usual"
+    /// type.
+    ///
+    /// \returns A pointer to a new LLVM type, possibly the same as the original
+    /// on success; 0 on failure.
     virtual llvm::Type* adjustInlineAsmType(CodeGen::CodeGenFunction &CGF,
-                                            StringRef Constraint, 
+                                            StringRef Constraint,
                                             llvm::Type* Ty) const {
       return Ty;
     }
diff --git a/test/CodeGen/mmx-inline-asm-error.c b/test/CodeGen/mmx-inline-asm-error.c
new file mode 100644
index 0000000..d5e0d18
--- /dev/null
+++ b/test/CodeGen/mmx-inline-asm-error.c
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -S -o - %s 2>&1 | FileCheck %s
+typedef int vec256 __attribute__((ext_vector_type(8)));
+
+vec256 foo(vec256 in) {
+  vec256 out;
+
+  asm("something %0" : : "y"(in));
+  asm("something %0" : "=y"(out));
+  asm("something %0, %0" : "+y"(out));
+
+  return out;
+// CHECK: error: invalid type 'vec256' in asm input for constraint 'y'
+// CHECK: error: invalid type 'vec256' in asm input for constraint 'y'
+// CHECK: error: invalid type 'vec256' in asm input for constraint 'y'
+// CHECK-NOT: invalid type
+}