[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.cpp

@@ -137,4 +137,12 @@ MachinePointerInfo MipsFunctionInfo::callPtrInfo(const GlobalValue *Val) {
   return MachinePointerInfo(E);
 }
 
+int MipsFunctionInfo::getBuildPairF64_FI(const TargetRegisterClass *RC) {
+  if (BuildPairF64_FI == -1) {
+    BuildPairF64_FI = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
+        RC->getAlignment(), false);
+  }
+  return BuildPairF64_FI;
+}
+
 void MipsFunctionInfo::anchor() { }