Define a feature for __float128 support in the PPC back end

This patch corresponds to review:
http://reviews.llvm.org/D15117

In preparation for supporting IEEE Quad precision floating point,
this patch simply defines a feature to specify the target supports this.
For now, nothing is done with the target feature, we just don't want
warnings from the Clang FE when a user specifies -mfloat128.
Calling convention and other related work will add to this patch in
the near future.

llvm-svn: 255642

llvm/lib/Target/PowerPC/PPC.td

@@ -141,6 +141,10 @@ def FeatureMFTB   : SubtargetFeature<"", "FeatureMFTB", "true",
                                         "Implement mftb using the mfspr instruction">;
 def FeatureFusion : SubtargetFeature<"fusion", "HasFusion", "true",
                                      "Target supports add/load integer fusion.">;
+def FeatureFloat128 :
+  SubtargetFeature<"float128", "HasFloat128", "true",
+                   "Enable the __float128 data type for IEEE-754R Binary128.",
+                   [FeatureVSX]>;
 
 def DeprecatedDST    : SubtargetFeature<"", "DeprecatedDST", "true",
   "Treat vector data stream cache control instructions as deprecated">;

llvm/lib/Target/PowerPC/PPCSubtarget.cpp

@@ -102,6 +102,7 @@ void PPCSubtarget::initializeEnvironment() {
   IsQPXStackUnaligned = false;
   HasHTM = false;
   HasFusion = false;
+  HasFloat128 = false;
 }
 
 void PPCSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {

llvm/lib/Target/PowerPC/PPCSubtarget.h

@@ -121,6 +121,7 @@ protected:
   bool HasDirectMove;
   bool HasHTM;
   bool HasFusion;
+  bool HasFloat128;
 
   /// When targeting QPX running a stock PPC64 Linux kernel where the stack
   /// alignment has not been changed, we need to keep the 16-byte alignment
@@ -259,6 +260,7 @@ public:
   }
   bool hasHTM() const { return HasHTM; }
   bool hasFusion() const { return HasFusion; }
+  bool hasFloat128() const { return HasFloat128; }
 
   const Triple &getTargetTriple() const { return TargetTriple; }