[mips] Expand BuildPairF64 to a spill and reload when the O32 FPXX ABI is

enabled and mthc1 and dmtc1 are not available (e.g. on MIPS32r1)

This prevents the upper 32-bits of a double precision value from being moved to
the FPU with mtc1 to an odd-numbered FPU register. This is necessary to ensure
that the code generated executes correctly regardless of the current FPU mode.

MIPS32r2 and above continues to use mtc1/mthc1, while MIPS-IV and above continue
to use dmtc1.

Differential Revision: http://reviews.llvm.org/D4465


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212930 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Mips/MipsMachineFunction.h

@@ -54,7 +54,8 @@ class MipsFunctionInfo : public MachineFunctionInfo {
 public:
   MipsFunctionInfo(MachineFunction &MF)
       : MF(MF), SRetReturnReg(0), GlobalBaseReg(0), Mips16SPAliasReg(0),
-        VarArgsFrameIndex(0), CallsEhReturn(false), SaveS2(false) {}
+        VarArgsFrameIndex(0), CallsEhReturn(false), SaveS2(false),
+        BuildPairF64_FI(-1) {}
 
   ~MipsFunctionInfo();
 
@@ -96,6 +97,8 @@ public:
   void setSaveS2() { SaveS2 = true; }
   bool hasSaveS2() const { return SaveS2; }
 
+  int getBuildPairF64_FI(const TargetRegisterClass *RC);
+
   std::map<const char *, const llvm::Mips16HardFloatInfo::FuncSignature *>
   StubsNeeded;
 
@@ -136,6 +139,10 @@ private:
   // saveS2
   bool SaveS2;
 
+  /// FrameIndex for expanding BuildPairF64 nodes to spill and reload when the
+  /// O32 FPXX ABI is enabled. -1 is used to denote invalid index.
+  int BuildPairF64_FI;
+
   /// MipsCallEntry maps.
   StringMap<const MipsCallEntry *> ExternalCallEntries;
   ValueMap<const GlobalValue *, const MipsCallEntry *> GlobalCallEntries;