[PowerPC] Add support for -mlongcall

The "long call" option forces the use of the indirect calling sequence for all
calls (even those that don't really need it). GCC provides this option; This is
helpful, under certain circumstances, for building very-large binaries, and
some other specialized use cases.

Fixes PR19098.

llvm-svn: 280040
diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.h b/llvm/lib/Target/PowerPC/PPCSubtarget.h
index 9fe286a..f58c7c1 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.h
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.h
@@ -132,6 +132,7 @@
   bool HasFusion;
   bool HasFloat128;
   bool IsISA3_0;
+  bool UseLongCalls;
 
   POPCNTDKind HasPOPCNTD;
 
@@ -275,6 +276,7 @@
   bool hasFusion() const { return HasFusion; }
   bool hasFloat128() const { return HasFloat128; }
   bool isISA3_0() const { return IsISA3_0; }
+  bool useLongCalls() const { return UseLongCalls; }
 
   POPCNTDKind hasPOPCNTD() const { return HasPOPCNTD; }