Index: lib/Target/Mips/MipsCallingConv.td
===================================================================
--- lib/Target/Mips/MipsCallingConv.td
+++ lib/Target/Mips/MipsCallingConv.td
@@ -123,7 +123,7 @@
 ]>;
 
 def CC_MipsN : CallingConv<[
-  CCIfType<[i8, i16, i32],
+  CCIfType<[i8, i16, i32, i64],
       CCIfSubtargetNot<"isLittle()",
           CCIfInReg<CCPromoteToUpperBitsInType<i64>>>>,
 
Index: test/CodeGen/Mips/cconv/arguments-small-structures-bigger-than-32bits.ll
===================================================================
--- test/CodeGen/Mips/cconv/arguments-small-structures-bigger-than-32bits.ll
+++ test/CodeGen/Mips/cconv/arguments-small-structures-bigger-than-32bits.ll
@@ -0,0 +1,73 @@
+; RUN: llc --march=mips64 -mcpu=mips64r2 < %s | FileCheck %s
+
+; #include <stdio.h>
+; 
+; struct S1 {
+;   char x1;
+;   short x2;
+;   char x3;
+; };
+; 
+; struct S2 {
+;   char x1;
+;   char x2;
+;   char x3;
+;   char x4;
+;   char x5;
+; };
+; 
+; void fS1(struct S1 s);
+; void fS2(struct S2 s);
+; 
+; void f1() {
+;   struct S1 s1_1;
+;   fS1(s1_1);
+; }
+; 
+; void f2() {
+;   struct S2 s2_1;
+;   fS2(s2_1);
+; }
+; 
+; int main() {
+;   f1();
+;   f2();
+; }
+
+%struct.S1 = type { i8, i16, i8 }
+%struct.S2 = type { i8, i8, i8, i8, i8 }
+
+declare void @fS1(i48 inreg) #1
+declare void @fS2(i40 inreg) #1
+
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1) #2
+
+define void @f1() #0 {
+entry:
+  %s1_1 = alloca %struct.S1, align 2
+  %s1_1.coerce = alloca { i48 }
+  %0 = bitcast { i48 }* %s1_1.coerce to i8*
+  %1 = bitcast %struct.S1* %s1_1 to i8*
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %0, i8* %1, i64 6, i32 0, i1 false)
+  %2 = getelementptr { i48 }, { i48 }* %s1_1.coerce, i32 0, i32 0
+  %3 = load i48, i48* %2, align 1
+  call void @fS1(i48 inreg %3)
+  ret void
+ ; CHECK-LABEL: f1:
+ ; CHECK: dsll $[[R1:[0-9]+]], $[[R2:[0-9]+]], 16
+}
+
+define void @f2() #0 {
+entry:
+  %s2_1 = alloca %struct.S2, align 1
+  %s2_1.coerce = alloca { i40 }
+  %0 = bitcast { i40 }* %s2_1.coerce to i8*
+  %1 = bitcast %struct.S2* %s2_1 to i8*
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %0, i8* %1, i64 5, i32 0, i1 false)
+  %2 = getelementptr { i40 }, { i40 }* %s2_1.coerce, i32 0, i32 0
+  %3 = load i40, i40* %2, align 1
+  call void @fS2(i40 inreg %3)
+  ret void
+ ; CHECK-LABEL: f2:
+ ; CHECK: dsll $[[R1:[0-9]+]], $[[R2:[0-9]+]], 24
+}