[RISCV] Remove overzealous is64Bit checks

lowerGlobalAddress, lowerBlockAddress, and insertIndirectBranch contain 
overzealous checks for is64Bit. These functions are all safe as-implemented 
for RV64.

llvm-svn: 343781
diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index 9cfd747..5c347ca 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -327,7 +327,7 @@
   int64_t Offset = N->getOffset();
   MVT XLenVT = Subtarget.getXLenVT();
 
-  if (isPositionIndependent() || Subtarget.is64Bit())
+  if (isPositionIndependent())
     report_fatal_error("Unable to lowerGlobalAddress");
   // In order to maximise the opportunity for common subexpression elimination,
   // emit a separate ADD node for the global address offset instead of folding
@@ -352,7 +352,7 @@
   const BlockAddress *BA = N->getBlockAddress();
   int64_t Offset = N->getOffset();
 
-  if (isPositionIndependent() || Subtarget.is64Bit())
+  if (isPositionIndependent())
     report_fatal_error("Unable to lowerBlockAddress");
 
   SDValue BAHi = DAG.getTargetBlockAddress(BA, Ty, Offset, RISCVII::MO_HI);