cortex m4 has floating point support, but only single precision.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110810 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARM.td

@@ -40,6 +40,8 @@ def FeatureDB     : SubtargetFeature<"db", "HasDataBarrier", "true",
                                    "Has data barrier (dmb / dsb) instructions">;
 def FeatureSlowFPBrcc : SubtargetFeature<"slow-fp-brcc", "SlowFPBrcc", "true",
                                          "FP compare + branch is slow">;
+def FeatureVFPOnlySP : SubtargetFeature<"fp-only-sp", "FPOnlySP", "true",
+                          "Floating point unit supports single precision only">;
 
 // Some processors have multiply-accumulate instructions that don't
 // play nicely with other VFP instructions, and it's generally better
@@ -155,7 +157,7 @@ def : Processor<"cortex-a9",        CortexA9Itineraries,
 
 // V7M Processors.
 def : ProcNoItin<"cortex-m3",       [ArchV7M]>;
-def : ProcNoItin<"cortex-m4",       [ArchV7M]>;
+def : ProcNoItin<"cortex-m4",       [ArchV7M, FeatureVFP2, FeatureVFPOnlySP]>;
 
 //===----------------------------------------------------------------------===//
 // Register File Description

lib/Target/ARM/ARMISelLowering.cpp

@@ -266,7 +266,8 @@ ARMTargetLowering::ARMTargetLowering(TargetMachine &TM)
     addRegisterClass(MVT::i32, ARM::GPRRegisterClass);
   if (!UseSoftFloat && Subtarget->hasVFP2() && !Subtarget->isThumb1Only()) {
     addRegisterClass(MVT::f32, ARM::SPRRegisterClass);
-    addRegisterClass(MVT::f64, ARM::DPRRegisterClass);
+    if (!Subtarget->isFPOnlySP())
+      addRegisterClass(MVT::f64, ARM::DPRRegisterClass);
 
     setTruncStoreAction(MVT::f64, MVT::f32, Expand);
   }

lib/Target/ARM/ARMSubtarget.cpp

@@ -45,6 +45,7 @@ ARMSubtarget::ARMSubtarget(const std::string &TT, const std::string &FS,
   , HasT2ExtractPack(false)
   , HasDataBarrier(false)
   , Pref32BitThumb(false)
+  , FPOnlySP(false)
   , stackAlignment(4)
   , CPUString("generic")
   , TargetType(isELF) // Default to ELF unless otherwise specified.

lib/Target/ARM/ARMSubtarget.h

@@ -95,6 +95,10 @@ protected:
   /// over 16-bit ones.
   bool Pref32BitThumb;
 
+  /// FPOnlySP - If true, the floating point unit only supports single
+  /// precision.
+  bool FPOnlySP;
+
   /// stackAlignment - The minimum alignment known to hold of the stack frame on
   /// entry to the function and which must be maintained by every function.
   unsigned stackAlignment;
@@ -151,6 +155,7 @@ protected:
   bool hasDataBarrier() const { return HasDataBarrier; }
   bool useVMLx() const {return hasVFP2() && !SlowVMLx; }
   bool isFPBrccSlow() const { return SlowFPBrcc; }
+  bool isFPOnlySP() const { return FPOnlySP; }
   bool prefers32BitThumb() const { return Pref32BitThumb; }
 
   bool hasFP16() const { return HasFP16; }