Index: lib/Target/Mips/MipsSEISelLowering.cpp
===================================================================
--- lib/Target/Mips/MipsSEISelLowering.cpp
+++ lib/Target/Mips/MipsSEISelLowering.cpp
@@ -28,7 +28,7 @@
 
 static cl::opt<bool>
 UseMipsTailCalls("mips-tail-calls", cl::Hidden,
-                    cl::desc("MIPS: permit tail calls."), cl::init(true));
+                    cl::desc("MIPS: permit tail calls."), cl::init(false));
 
 static cl::opt<bool> NoDPLoadStore("mno-ldc1-sdc1", cl::init(false),
                                    cl::desc("Expand double precision loads and "
Index: test/CodeGen/Mips/fastcc.ll
===================================================================
--- test/CodeGen/Mips/fastcc.ll
+++ test/CodeGen/Mips/fastcc.ll
@@ -1,8 +1,8 @@
 ; RUN: llc < %s -march=mipsel -relocation-model=pic | FileCheck %s
-; RUN: llc < %s -mtriple=mipsel-none-nacl-gnu -relocation-model=pic \
+; RUN: llc < %s -mtriple=mipsel-none-nacl-gnu -relocation-model=pic -mips-tail-calls=1\
 ; RUN:  | FileCheck %s -check-prefix=CHECK-NACL
-; RUN: llc < %s -march=mipsel -mcpu=mips32 -mattr=+nooddspreg -relocation-model=pic | FileCheck %s -check-prefix=NOODDSPREG
-; RUN: llc < %s -march=mipsel -mcpu=mips32r2 -mattr=+fp64,+nooddspreg -relocation-model=pic | FileCheck %s -check-prefix=FP64-NOODDSPREG
+; RUN: llc < %s -march=mipsel -mcpu=mips32 -mattr=+nooddspreg -relocation-model=pic -mips-tail-calls=1| FileCheck %s -check-prefix=NOODDSPREG
+; RUN: llc < %s -march=mipsel -mcpu=mips32r2 -mattr=+fp64,+nooddspreg -relocation-model=pic -mips-tail-calls=1 | FileCheck %s -check-prefix=FP64-NOODDSPREG
 
 
 @gi0 = external global i32
Index: test/CodeGen/Mips/gpreg-lazy-binding.ll
===================================================================
--- test/CodeGen/Mips/gpreg-lazy-binding.ll
+++ test/CodeGen/Mips/gpreg-lazy-binding.ll
@@ -1,4 +1,4 @@
-; RUN: llc -march=mipsel -disable-mips-delay-filler -relocation-model=pic < %s | FileCheck %s
+; RUN: llc -march=mipsel -disable-mips-delay-filler -relocation-model=pic -mips-tail-calls=1 < %s | FileCheck %s
 
 @g = external global i32
 
Index: test/CodeGen/Mips/i64arg.ll
===================================================================
--- test/CodeGen/Mips/i64arg.ll
+++ test/CodeGen/Mips/i64arg.ll
@@ -1,4 +1,4 @@
-; RUN: llc -march=mips -relocation-model=pic < %s | FileCheck %s
+; RUN: llc -march=mips -relocation-model=pic -mips-tail-calls=1 < %s | FileCheck %s
 
 define void @f1(i64 %ll1, float %f, i64 %ll, i32 %i, float %f2) nounwind {
 entry:
Index: test/CodeGen/Mips/indirectcall.ll
===================================================================
--- test/CodeGen/Mips/indirectcall.ll
+++ test/CodeGen/Mips/indirectcall.ll
@@ -1,4 +1,4 @@
-; RUN: llc  < %s -march=mipsel -relocation-model=static | FileCheck %s 
+; RUN: llc  < %s -march=mipsel -relocation-model=static -mips-tail-calls=1 | FileCheck %s 
 
 define void @foo0(void (i32)* nocapture %f1) nounwind {
 entry:
Index: test/CodeGen/Mips/lazy-binding.ll
===================================================================
--- test/CodeGen/Mips/lazy-binding.ll
+++ test/CodeGen/Mips/lazy-binding.ll
@@ -1,4 +1,4 @@
-; RUN: llc -march=mipsel -relocation-model=pic < %s | FileCheck %s
+; RUN: llc -march=mipsel -relocation-model=pic -mips-tail-calls=1 < %s | FileCheck %s
 
 ; CHECK-LABEL: foo6:
 ; CHECK: %while.body
Index: test/CodeGen/Mips/llvm-ir/call.ll
===================================================================
--- test/CodeGen/Mips/llvm-ir/call.ll
+++ test/CodeGen/Mips/llvm-ir/call.ll
@@ -1,29 +1,29 @@
 ; Test the 'call' instruction and the tailcall variant.
 
-; RUN: llc -march=mips   -mcpu=mips32   -relocation-model=pic  < %s | FileCheck %s -check-prefixes=ALL,O32,NOT-R6C
-; RUN: llc -march=mips   -mcpu=mips32r2 -relocation-model=pic  < %s | FileCheck %s -check-prefixes=ALL,O32,NOT-R6C
-; RUN: llc -march=mips   -mcpu=mips32r3 -relocation-model=pic  < %s | FileCheck %s -check-prefixes=ALL,O32,NOT-R6C
-; RUN: llc -march=mips   -mcpu=mips32r5 -relocation-model=pic  < %s | FileCheck %s -check-prefixes=ALL,O32,NOT-R6C
-; RUN: llc -march=mips   -mcpu=mips32r6 -relocation-model=pic -disable-mips-delay-filler  < %s | FileCheck %s -check-prefixes=ALL,O32,R6C
-; RUN: llc -march=mips   -mcpu=mips32r6 -relocation-model=pic -mattr=+fp64,+nooddspreg -disable-mips-delay-filler  < %s | FileCheck %s -check-prefixes=ALL,O32,R6C
-; RUN: llc -march=mips64 -mcpu=mips4     < %s | FileCheck %s -check-prefixes=ALL,N64,NOT-R6C
-; RUN: llc -march=mips64 -mcpu=mips64    < %s | FileCheck %s -check-prefixes=ALL,N64,NOT-R6C
-; RUN: llc -march=mips64 -mcpu=mips64r2  < %s | FileCheck %s -check-prefixes=ALL,N64,NOT-R6C
-; RUN: llc -march=mips64 -mcpu=mips64r3  < %s | FileCheck %s -check-prefixes=ALL,N64,NOT-R6C
-; RUN: llc -march=mips64 -mcpu=mips64r5  < %s | FileCheck %s -check-prefixes=ALL,N64,NOT-R6C
-; RUN: llc -march=mips64 -mcpu=mips64r6 -disable-mips-delay-filler  < %s | FileCheck %s -check-prefixes=ALL,N64,R6C
-; RUN: llc -march=mips   -mcpu=mips32   -relocation-model=pic  < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=NOT-R6C
-; RUN: llc -march=mips   -mcpu=mips32r2 -relocation-model=pic  < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=NOT-R6C
-; RUN: llc -march=mips   -mcpu=mips32r3 -relocation-model=pic  < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=NOT-R6C
-; RUN: llc -march=mips   -mcpu=mips32r5 -relocation-model=pic  < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=NOT-R6C
-; RUN: llc -march=mips   -mcpu=mips32r6 -relocation-model=pic -disable-mips-delay-filler  < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=R6C
-; RUN: llc -march=mips   -mcpu=mips32r6 -relocation-model=pic -mattr=+fp64,+nooddspreg -disable-mips-delay-filler  < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=R6C
-; RUN: llc -march=mips64 -mcpu=mips4     < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=NOT-R6C
-; RUN: llc -march=mips64 -mcpu=mips64    < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=NOT-R6C
-; RUN: llc -march=mips64 -mcpu=mips64r2  < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=NOT-R6C
-; RUN: llc -march=mips64 -mcpu=mips64r3  < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=NOT-R6C
-; RUN: llc -march=mips64 -mcpu=mips64r5  < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=NOT-R6C
-; RUN: llc -march=mips64 -mcpu=mips64r6 -disable-mips-delay-filler  < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=R6C
+; RUN: llc -march=mips   -mcpu=mips32   -relocation-model=pic  -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,O32,NOT-R6C
+; RUN: llc -march=mips   -mcpu=mips32r2 -relocation-model=pic  -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,O32,NOT-R6C
+; RUN: llc -march=mips   -mcpu=mips32r3 -relocation-model=pic  -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,O32,NOT-R6C
+; RUN: llc -march=mips   -mcpu=mips32r5 -relocation-model=pic  -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,O32,NOT-R6C
+; RUN: llc -march=mips   -mcpu=mips32r6 -relocation-model=pic -disable-mips-delay-filler  -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,O32,R6C
+; RUN: llc -march=mips   -mcpu=mips32r6 -relocation-model=pic -mattr=+fp64,+nooddspreg -disable-mips-delay-filler  -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,O32,R6C
+; RUN: llc -march=mips64 -mcpu=mips4     -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,N64,NOT-R6C
+; RUN: llc -march=mips64 -mcpu=mips64    -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,N64,NOT-R6C
+; RUN: llc -march=mips64 -mcpu=mips64r2  -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,N64,NOT-R6C
+; RUN: llc -march=mips64 -mcpu=mips64r3  -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,N64,NOT-R6C
+; RUN: llc -march=mips64 -mcpu=mips64r5  -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,N64,NOT-R6C
+; RUN: llc -march=mips64 -mcpu=mips64r6 -disable-mips-delay-filler  -mips-tail-calls=1 < %s | FileCheck %s -check-prefixes=ALL,N64,R6C
+; RUN: llc -march=mips   -mcpu=mips32   -relocation-model=pic  -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=NOT-R6C
+; RUN: llc -march=mips   -mcpu=mips32r2 -relocation-model=pic  -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=NOT-R6C
+; RUN: llc -march=mips   -mcpu=mips32r3 -relocation-model=pic  -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=NOT-R6C
+; RUN: llc -march=mips   -mcpu=mips32r5 -relocation-model=pic  -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=NOT-R6C
+; RUN: llc -march=mips   -mcpu=mips32r6 -relocation-model=pic -disable-mips-delay-filler  -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=R6C
+; RUN: llc -march=mips   -mcpu=mips32r6 -relocation-model=pic -mattr=+fp64,+nooddspreg -disable-mips-delay-filler  -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=O32 -check-prefix=R6C
+; RUN: llc -march=mips64 -mcpu=mips4     -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=NOT-R6C
+; RUN: llc -march=mips64 -mcpu=mips64    -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=NOT-R6C
+; RUN: llc -march=mips64 -mcpu=mips64r2  -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=NOT-R6C
+; RUN: llc -march=mips64 -mcpu=mips64r3  -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=NOT-R6C
+; RUN: llc -march=mips64 -mcpu=mips64r5  -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=NOT-R6C
+; RUN: llc -march=mips64 -mcpu=mips64r6 -disable-mips-delay-filler  -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=ALL -check-prefix=N64 -check-prefix=R6C
 
 declare void @extern_void_void()
 declare i32 @extern_i32_void()
Index: test/CodeGen/Mips/tailcall/tail-call-arguments-clobber.ll
===================================================================
--- test/CodeGen/Mips/tailcall/tail-call-arguments-clobber.ll
+++ test/CodeGen/Mips/tailcall/tail-call-arguments-clobber.ll
@@ -1,9 +1,9 @@
-; RUN: llc -march=mips -mcpu=mips32 -O0 -relocation-model=pic < %s | FileCheck \
+; RUN: llc -march=mips -mcpu=mips32 -O0 -relocation-model=pic -mips-tail-calls=1 < %s | FileCheck \
 ; RUN:     %s -check-prefix=MIPS32
 ; RUN: llc -march=mips64 -mcpu=mips64 -O0 -relocation-model=pic -target-abi n64 \
-; RUN:     < %s | FileCheck %s -check-prefix=MIPS64
+; RUN:     -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=MIPS64
 ; RUN: llc -march=mips64 -mcpu=mips64 -O0 -relocation-model=pic -target-abi n32 \
-; RUN:     < %s | FileCheck %s -check-prefix=MIPS64
+; RUN:     -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=MIPS64
 
 
 ; LLVM PR/30197
Index: test/CodeGen/Mips/tailcall/tailcall-wrong-isa.ll
===================================================================
--- test/CodeGen/Mips/tailcall/tailcall-wrong-isa.ll
+++ test/CodeGen/Mips/tailcall/tailcall-wrong-isa.ll
@@ -1,24 +1,24 @@
-; RUN: llc -filetype=obj -march=mipsel -relocation-model=pic -verify-machineinstrs < %s -o - \
+; RUN: llc -filetype=obj -march=mipsel -relocation-model=pic -verify-machineinstrs -mips-tail-calls=1 < %s -o - \
 ; RUN:   | llvm-objdump  -d - | FileCheck %s -check-prefix=PIC32
 
-; RUN: llc -filetype=obj -march=mipsel -relocation-model=static -verify-machineinstrs < %s -o - \
+; RUN: llc -filetype=obj -march=mipsel -relocation-model=static -verify-machineinstrs -mips-tail-calls=1 < %s -o - \
 ; RUN:   | llvm-objdump  -d - | FileCheck %s -check-prefix=STATIC32
 
-; RUN: llc -filetype=obj -march=mips64el -mcpu=mips64 -verify-machineinstrs < %s -o - \
+; RUN: llc -filetype=obj -march=mips64el -mcpu=mips64 -verify-machineinstrs -mips-tail-calls=1 < %s -o - \
 ; RUN:   | llvm-objdump  -d - | FileCheck %s -check-prefix=N64
 
-; RUN: llc -filetype=obj -march=mipsel -relocation-model=pic -mattr=+micromips < %s -o - \
+; RUN: llc -filetype=obj -march=mipsel -relocation-model=pic -mattr=+micromips -mips-tail-calls=1 < %s -o - \
 ; RUN:   | llvm-objdump  -d - | FileCheck %s -check-prefix=PIC32MM
 
-; RUN: llc -filetype=obj -march=mipsel -relocation-model=static -mattr=+micromips < %s -o - \
+; RUN: llc -filetype=obj -march=mipsel -relocation-model=static -mattr=+micromips -mips-tail-calls=1 < %s -o - \
 ; RUN:   | llvm-objdump  -d - | FileCheck %s -check-prefix=STATIC32MM
 
-; RUN: llc -filetype=obj -march=mipsel -relocation-model=pic -mcpu=mips32r6 < %s -o - \
+; RUN: llc -filetype=obj -march=mipsel -relocation-model=pic -mcpu=mips32r6 -mips-tail-calls=1 < %s -o - \
 ; RUN:   | llvm-objdump  -d - | FileCheck %s  -check-prefix=PIC32R6
-; RUN: llc -filetype=obj -march=mipsel -relocation-model=static -mcpu=mips32r6 < %s -o - \
+; RUN: llc -filetype=obj -march=mipsel -relocation-model=static -mcpu=mips32r6 -mips-tail-calls=1 < %s -o - \
 ; RUN:   | llvm-objdump  -d - | FileCheck %s -check-prefix=STATIC32R6
 
-; RUN: llc -filetype=obj -march=mips64el -mcpu=mips64r6 < %s -o - \
+; RUN: llc -filetype=obj -march=mips64el -mcpu=mips64r6 -mips-tail-calls=1 < %s -o - \
 ; RUN:   | llvm-objdump  -d - | FileCheck %s -check-prefix=N64R6
 
 declare i8 @f2(i8)
Index: test/CodeGen/Mips/tailcall/tailcall.ll
===================================================================
--- test/CodeGen/Mips/tailcall/tailcall.ll
+++ test/CodeGen/Mips/tailcall/tailcall.ll
@@ -1,30 +1,30 @@
 ; RUN: llc -march=mipsel -relocation-model=pic  \
-; RUN:     -verify-machineinstrs < %s | FileCheck %s -check-prefix=PIC32
+; RUN:     -verify-machineinstrs -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=PIC32
 ; RUN: llc -march=mipsel -relocation-model=static  \
-; RUN:     -verify-machineinstrs < %s | FileCheck %s -check-prefix=STATIC32
+; RUN:     -verify-machineinstrs -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=STATIC32
 ; RUN: llc -march=mips64el -mcpu=mips64r2  \
-; RUN:     -verify-machineinstrs < %s | FileCheck %s -check-prefix=N64
+; RUN:     -verify-machineinstrs -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=N64
 ; RUN: llc -march=mipsel -mattr=mips16 -relocation-model=pic \
-; RUN:      -verify-machineinstrs < %s | \
+; RUN:      -verify-machineinstrs -mips-tail-calls=1 < %s | \
 ; RUN:     FileCheck %s -check-prefix=PIC16
 
-; RUN: llc -march=mipsel -relocation-model=pic -mattr=+micromips < %s | \
+; RUN: llc -march=mipsel -relocation-model=pic -mattr=+micromips -mips-tail-calls=1 < %s | \
 ; RUN:     FileCheck %s -check-prefix=PIC32
 ; RUN: llc -march=mipsel -relocation-model=static -mattr=+micromips \
-; RUN:     < %s | FileCheck %s -check-prefix=STATIC32
+; RUN:     -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=STATIC32
 
-; RUN: llc -march=mipsel -relocation-model=pic -mcpu=mips32r6 < %s | \
+; RUN: llc -march=mipsel -relocation-model=pic -mcpu=mips32r6 -mips-tail-calls=1 < %s | \
 ; RUN:     FileCheck %s -check-prefix=PIC32
 ; RUN: llc -march=mipsel -relocation-model=static -mcpu=mips32r6 \
-; RUN:     < %s | FileCheck %s -check-prefix=STATIC32
+; RUN:     -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=STATIC32
 ; RUN: llc -march=mips64el -mcpu=mips64r6  \
-; RUN:     < %s | FileCheck %s -check-prefix=N64
+; RUN:     -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=N64
 
 ; RUN: llc -march=mipsel -relocation-model=pic -mcpu=mips32r6 -mattr=+micromips \
-; RUN:      < %s | FileCheck %s -check-prefix=PIC32
+; RUN:      -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=PIC32
 ; RUN: llc -march=mipsel -relocation-model=static -mcpu=mips32r6 \
-; RUN:     -mattr=+micromips < %s | FileCheck %s -check-prefix=STATIC32
-; RUN: llc -march=mips64el -mcpu=mips64r6 -mattr=+micromips < %s \
+; RUN:     -mattr=+micromips -mips-tail-calls=1 < %s | FileCheck %s -check-prefix=STATIC32
+; RUN: llc -march=mips64el -mcpu=mips64r6 -mattr=+micromips -mips-tail-calls=1 < %s \
 ; RUN:      | FileCheck %s -check-prefix=N64
 
 @g0 = common global i32 0, align 4