Index: lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp
===================================================================
--- lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp
+++ lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp
@@ -92,6 +92,15 @@
   if (CM == CodeModel::JITDefault)
     RM = Reloc::Static;
   else if (RM == Reloc::Default)
+    // We currently default to PIC code generation.  This differs from
+    // other architectures, such as x86 and ARM, and from GCC's handling of
+    // MIPS.  The reasons for defaulting to PIC appear to be historical.
+    // It used to be the case that the linker did not support producing
+    // dynamically-linked executables containing non-position-independent
+    // code on MIPS.
+    // TODO: Linker support for non-PIC was added in 2008, so it may be
+    // possible to make non-PIC the default here now, which would have the
+    // benefit of generating slightly faster code.
     RM = Reloc::PIC_;
   X->InitMCCodeGenInfo(RM, CM, OL);
   return X;