1 files changed, 36 insertions, 2 deletions
diff --git a/lib/Basic/Targets.cpp b/lib/Basic/Targets.cpp
index 638d6a028c..6b376b30ad 100644
--- a/lib/Basic/Targets.cpp
+++ b/lib/Basic/Targets.cpp
@@ -3527,6 +3527,34 @@ class ARMTargetInfo : public TargetInfo {
 
   static const Builtin::Info BuiltinInfo[];
 
+  static bool shouldUseInlineAtomic(const llvm::Triple &T) {
+    // On linux, binaries targeting old cpus call functions in libgcc to
+    // perform atomic operations. The implementation in libgcc then calls into
+    // the kernel which on armv6 and newer uses ldrex and strex. The net result
+    // is that if we assume the kernel is at least as recent as the hardware,
+    // it is safe to use atomic instructions on armv6 and newer.
+    if (T.getOS() != llvm::Triple::Linux)
+     return false;
+    StringRef ArchName = T.getArchName();
+    if (T.getArch() == llvm::Triple::arm) {
+      if (!ArchName.startswith("armv"))
+        return false;
+      StringRef VersionStr = ArchName.substr(4);
+      unsigned Version;
+      if (VersionStr.getAsInteger(10, Version))
+        return false;
+      return Version >= 6;
+    }
+    assert(T.getArch() == llvm::Triple::thumb);
+    if (!ArchName.startswith("thumbv"))
+      return false;
+    StringRef VersionStr = ArchName.substr(6);
+    unsigned Version;
+    if (VersionStr.getAsInteger(10, Version))
+      return false;
+    return Version >= 7;
+  }
+
 public:
   ARMTargetInfo(const std::string &TripleStr)
     : TargetInfo(TripleStr), ABI("aapcs-linux"), CPU("arm1136j-s"), IsAAPCS(true)
@@ -3559,8 +3587,9 @@ public:
     TheCXXABI.set(TargetCXXABI::GenericARM);
 
     // ARM has atomics up to 8 bytes
-    // FIXME: Set MaxAtomicInlineWidth if we have the feature v6e
-    MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64;
+    MaxAtomicPromoteWidth = 64;
+    if (shouldUseInlineAtomic(getTriple()))
+      MaxAtomicInlineWidth = 64;
 
     // Do force alignment of members that follow zero length bitfields.  If
     // the alignment of the zero-length bitfield is greater than the member 
@@ -4275,6 +4304,11 @@ public:
     // FIXME: Support Sparc quad-precision long double?
     DescriptionString = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-"
                         "i64:64:64-f32:32:32-f64:64:64-v64:64:64-n32:64-S128";
+    // This is an LP64 platform.
+    LongWidth = LongAlign = PointerWidth = PointerAlign = 64;
+    IntMaxType = SignedLong;
+    UIntMaxType = UnsignedLong;
+    Int64Type = SignedLong;
   }
 
   virtual void getTargetDefines(const LangOptions &Opts,