Add support for passing variables declared to use a xmm register to asm
statements using the "x" constraint.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@122679 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGStmt.cpp b/lib/CodeGen/CGStmt.cpp
index 8ccd289..b86cdf8 100644
--- a/lib/CodeGen/CGStmt.cpp
+++ b/lib/CodeGen/CGStmt.cpp
@@ -938,7 +938,8 @@
     return Constraint;
   llvm::StringRef Register = Attr->getLabel();
   assert(Target.isValidGCCRegisterName(Register));
-  if (Constraint != "r") {
+  // FIXME: We should check which registers are compatible with "r" or "x".
+  if (Constraint != "r" && Constraint != "x") {
     CGM.ErrorUnsupported(&Stmt, "__asm__");
     return Constraint;
   }