Index: include/llvm/ADT/Triple.h
===================================================================
--- include/llvm/ADT/Triple.h
+++ include/llvm/ADT/Triple.h
@@ -377,6 +377,8 @@
     return getOS() == Triple::FreeBSD;
   }
 
+  bool isOSDragonFly() const { return getOS() == Triple::DragonFly; }
+
   bool isOSSolaris() const {
     return getOS() == Triple::Solaris;
   }
Index: lib/Target/X86/X86FrameLowering.cpp
===================================================================
--- lib/Target/X86/X86FrameLowering.cpp
+++ lib/Target/X86/X86FrameLowering.cpp
@@ -1478,8 +1478,9 @@
 
   if (MF.getFunction()->isVarArg())
     report_fatal_error("Segmented stacks do not support vararg functions.");
-  if (!STI.isTargetLinux() && !STI.isTargetDarwin() &&
-      !STI.isTargetWin32() && !STI.isTargetWin64() && !STI.isTargetFreeBSD())
+  if (!STI.isTargetLinux() && !STI.isTargetDarwin() && !STI.isTargetWin32() &&
+      !STI.isTargetWin64() && !STI.isTargetFreeBSD() &&
+      !STI.isTargetDragonFly())
     report_fatal_error("Segmented stacks not supported on this platform.");
 
   // Eventually StackSize will be calculated by a link-time pass; which will
@@ -1533,6 +1534,9 @@
     } else if (STI.isTargetFreeBSD()) {
       TlsReg = X86::FS;
       TlsOffset = 0x18;
+    } else if (STI.isTargetDragonFly()) {
+      TlsReg = X86::FS;
+      TlsOffset = 0x20; // use tls_tcb.tcb_segstack
     } else {
       report_fatal_error("Segmented stacks not supported on this platform.");
     }
@@ -1555,6 +1559,9 @@
     } else if (STI.isTargetWin32()) {
       TlsReg = X86::FS;
       TlsOffset = 0x14; // pvArbitrary, reserved for application use
+    } else if (STI.isTargetDragonFly()) {
+      TlsReg = X86::FS;
+      TlsOffset = 0x10; // use tls_tcb.tcb_segstack
     } else if (STI.isTargetFreeBSD()) {
       report_fatal_error("Segmented stacks not supported on FreeBSD i386.");
     } else {
@@ -1567,7 +1574,8 @@
       BuildMI(checkMBB, DL, TII.get(X86::LEA32r), ScratchReg).addReg(X86::ESP)
         .addImm(1).addReg(0).addImm(-StackSize).addReg(0);
 
-    if (STI.isTargetLinux() || STI.isTargetWin32() || STI.isTargetWin64()) {
+    if (STI.isTargetLinux() || STI.isTargetWin32() || STI.isTargetWin64() ||
+        STI.isTargetDragonFly()) {
       BuildMI(checkMBB, DL, TII.get(X86::CMP32rm)).addReg(ScratchReg)
         .addReg(0).addImm(0).addReg(0).addImm(TlsOffset).addReg(TlsReg);
     } else if (STI.isTargetDarwin()) {
Index: lib/Target/X86/X86Subtarget.h
===================================================================
--- lib/Target/X86/X86Subtarget.h
+++ lib/Target/X86/X86Subtarget.h
@@ -404,6 +404,7 @@
 
   bool isTargetDarwin() const { return TargetTriple.isOSDarwin(); }
   bool isTargetFreeBSD() const { return TargetTriple.isOSFreeBSD(); }
+  bool isTargetDragonFly() const { return TargetTriple.isOSDragonFly(); }
   bool isTargetSolaris() const { return TargetTriple.isOSSolaris(); }
 
   bool isTargetELF() const { return TargetTriple.isOSBinFormatELF(); }
Index: test/CodeGen/X86/segmented-stacks.ll
===================================================================
--- test/CodeGen/X86/segmented-stacks.ll
+++ test/CodeGen/X86/segmented-stacks.ll
@@ -5,6 +5,8 @@
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-darwin -verify-machineinstrs | FileCheck %s -check-prefix=X64-Darwin
 ; RUN: llc < %s -mcpu=generic -mtriple=i686-mingw32 -verify-machineinstrs | FileCheck %s -check-prefix=X32-MinGW
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-freebsd -verify-machineinstrs | FileCheck %s -check-prefix=X64-FreeBSD
+; RUN: llc < %s -mcpu=generic -mtriple=i686-dragonfly -verify-machineinstrs | FileCheck %s -check-prefix=X32-DFlyBSD
+; RUN: llc < %s -mcpu=generic -mtriple=x86_64-dragonfly -verify-machineinstrs | FileCheck %s -check-prefix=X64-DFlyBSD
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-mingw32 -verify-machineinstrs | FileCheck %s -check-prefix=X64-MinGW
 
 ; We used to crash with filetype=obj
@@ -15,6 +17,8 @@
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-darwin -filetype=obj
 ; RUN: llc < %s -mcpu=generic -mtriple=i686-mingw32 -filetype=obj
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-freebsd -filetype=obj
+; RUN: llc < %s -mcpu=generic -mtriple=i686-dragonfly -filetype=obj
+; RUN: llc < %s -mcpu=generic -mtriple=x86_64-dragonfly -filetype=obj
 ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-mingw32 -filetype=obj
 
 ; RUN: not llc < %s -mcpu=generic -mtriple=x86_64-solaris 2> %t.log
@@ -114,6 +118,26 @@
 ; X64-FreeBSD-NEXT:  callq __morestack
 ; X64-FreeBSD-NEXT:  ret
 
+; X32-DFlyBSD-LABEL:       test_basic:
+
+; X32-DFlyBSD:       cmpl %fs:16, %esp
+; X32-DFlyBSD-NEXT:  ja      .LBB0_2
+
+; X32-DFlyBSD:       pushl $0
+; X32-DFlyBSD-NEXT:  pushl $48
+; X32-DFlyBSD-NEXT:  calll __morestack
+; X32-DFlyBSD-NEXT:  ret
+
+; X64-DFlyBSD-LABEL:       test_basic:
+
+; X64-DFlyBSD:       cmpq %fs:32, %rsp
+; X64-DFlyBSD-NEXT:  ja      .LBB0_2
+
+; X64-DFlyBSD:       movabsq $40, %r10
+; X64-DFlyBSD-NEXT:  movabsq $0, %r11
+; X64-DFlyBSD-NEXT:  callq __morestack
+; X64-DFlyBSD-NEXT:  ret
+
 }
 
 define i32 @test_nested(i32 * nest %closure, i32 %other) #0 {
@@ -199,6 +223,24 @@
 ; X64-FreeBSD-NEXT:  ret
 ; X64-FreeBSD-NEXT:  movq %rax, %r10
 
+; X32-DFlyBSD:       cmpl %fs:16, %esp
+; X32-DFlyBSD-NEXT:  ja      .LBB1_2
+
+; X32-DFlyBSD:       pushl $4
+; X32-DFlyBSD-NEXT:  pushl $52
+; X32-DFlyBSD-NEXT:  calll __morestack
+; X32-DFlyBSD-NEXT:  ret
+
+; X64-DFlyBSD:       cmpq %fs:32, %rsp
+; X64-DFlyBSD-NEXT:  ja      .LBB1_2
+
+; X64-DFlyBSD:       movq %r10, %rax
+; X64-DFlyBSD-NEXT:  movabsq $56, %r10
+; X64-DFlyBSD-NEXT:  movabsq $0, %r11
+; X64-DFlyBSD-NEXT:  callq __morestack
+; X64-DFlyBSD-NEXT:  ret
+; X64-DFlyBSD-NEXT:  movq %rax, %r10
+
 }
 
 define void @test_large() #0 {
@@ -280,6 +322,24 @@
 ; X64-FreeBSD-NEXT:  callq __morestack
 ; X64-FreeBSD-NEXT:  ret
 
+; X32-DFlyBSD:       leal -40008(%esp), %ecx
+; X32-DFlyBSD-NEXT:  cmpl %fs:16, %ecx
+; X32-DFlyBSD-NEXT:  ja      .LBB2_2
+
+; X32-DFlyBSD:       pushl $0
+; X32-DFlyBSD-NEXT:  pushl $40008
+; X32-DFlyBSD-NEXT:  calll __morestack
+; X32-DFlyBSD-NEXT:  ret
+
+; X64-DFlyBSD:       leaq -40008(%rsp), %r11
+; X64-DFlyBSD-NEXT:  cmpq %fs:32, %r11
+; X64-DFlyBSD-NEXT:  ja      .LBB2_2
+
+; X64-DFlyBSD:       movabsq $40008, %r10
+; X64-DFlyBSD-NEXT:  movabsq $0, %r11
+; X64-DFlyBSD-NEXT:  callq __morestack
+; X64-DFlyBSD-NEXT:  ret
+
 }
 
 define fastcc void @test_fastcc() #0 {
@@ -368,6 +428,26 @@
 ; X64-FreeBSD-NEXT:  callq __morestack
 ; X64-FreeBSD-NEXT:  ret
 
+; X32-DFlyBSD-LABEL:       test_fastcc:
+
+; X32-DFlyBSD:       cmpl %fs:16, %esp
+; X32-DFlyBSD-NEXT:  ja      .LBB3_2
+
+; X32-DFlyBSD:       pushl $0
+; X32-DFlyBSD-NEXT:  pushl $48
+; X32-DFlyBSD-NEXT:  calll __morestack
+; X32-DFlyBSD-NEXT:  ret
+
+; X64-DFlyBSD-LABEL:       test_fastcc:
+
+; X64-DFlyBSD:       cmpq %fs:32, %rsp
+; X64-DFlyBSD-NEXT:  ja      .LBB3_2
+
+; X64-DFlyBSD:       movabsq $40, %r10
+; X64-DFlyBSD-NEXT:  movabsq $0, %r11
+; X64-DFlyBSD-NEXT:  callq __morestack
+; X64-DFlyBSD-NEXT:  ret
+
 }
 
 define fastcc void @test_fastcc_large() #0 {
@@ -464,6 +544,28 @@
 ; X64-FreeBSD-NEXT:  callq __morestack
 ; X64-FreeBSD-NEXT:  ret
 
+; X32-DFlyBSD-LABEL:       test_fastcc_large:
+
+; X32-DFlyBSD:       leal -40008(%esp), %eax
+; X32-DFlyBSD-NEXT:  cmpl %fs:16, %eax
+; X32-DFlyBSD-NEXT:  ja      .LBB4_2
+
+; X32-DFlyBSD:       pushl $0
+; X32-DFlyBSD-NEXT:  pushl $40008
+; X32-DFlyBSD-NEXT:  calll __morestack
+; X32-DFlyBSD-NEXT:  ret
+
+; X64-DFlyBSD-LABEL:       test_fastcc_large:
+
+; X64-DFlyBSD:       leaq -40008(%rsp), %r11
+; X64-DFlyBSD-NEXT:  cmpq %fs:32, %r11
+; X64-DFlyBSD-NEXT:  ja      .LBB4_2
+
+; X64-DFlyBSD:       movabsq $40008, %r10
+; X64-DFlyBSD-NEXT:  movabsq $0, %r11
+; X64-DFlyBSD-NEXT:  callq __morestack
+; X64-DFlyBSD-NEXT:  ret
+
 }
 
 define fastcc void @test_fastcc_large_with_ecx_arg(i32 %a) #0 {
@@ -515,6 +617,12 @@
 
 ; X64-FreeBSD-LABEL: test_nostack:
 ; X64-FreeBSD-NOT:   callq __morestack
+
+; X32-DFlyBSD-LABEL: test_nostack:
+; X32-DFlyBSD-NOT:   calll __morestack
+
+; X64-DFlyBSD-LABEL: test_nostack:
+; X64-DFlyBSD-NOT:   callq __morestack
 }
 
 attributes #0 = { "split-stack" }