[mips] Support 16-bit offsets for 'm' inline assembly memory constraint.

Reviewers: vkalintiris

Reviewed By: vkalintiris

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8435

llvm-svn: 233086
diff --git a/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp b/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp
index 252f9b6..a598c3f 100644
--- a/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp
+++ b/llvm/lib/Target/Mips/MipsSEISelDAGToDAG.cpp
@@ -948,11 +948,19 @@
     llvm_unreachable("Unexpected asm memory constraint");
   // All memory constraints can at least accept raw pointers.
   case InlineAsm::Constraint_i:
-  case InlineAsm::Constraint_m:
   case InlineAsm::Constraint_R:
     OutOps.push_back(Op);
     OutOps.push_back(CurDAG->getTargetConstant(0, MVT::i32));
     return false;
+  case InlineAsm::Constraint_m:
+    if (selectAddrRegImm16(Op, Base, Offset)) {
+      OutOps.push_back(Base);
+      OutOps.push_back(Offset);
+      return false;
+    }
+    OutOps.push_back(Op);
+    OutOps.push_back(CurDAG->getTargetConstant(0, MVT::i32));
+    return false;
   case InlineAsm::Constraint_ZC:
     // ZC matches whatever the pref, ll, and sc instructions can handle for the
     // given subtarget.