Index: include/llvm/Target/TargetLowering.h
===================================================================
--- include/llvm/Target/TargetLowering.h
+++ include/llvm/Target/TargetLowering.h
@@ -169,6 +169,13 @@
 
   virtual bool useSoftFloat() const { return false; }
 
+  /// A target may require that no pointer passed from one function to another
+  /// points to the main stack.  Such a target must override this function to
+  /// return true.  SafeStack must always be used for such a target, to move
+  /// any stack allocation to the unsafe stack that is the target of a pointer
+  /// passed to a subroutine.
+  virtual bool useOnlyLocalStackPointers() const { return false; }
+
   /// Return the pointer type for the given address space, defaults to
   /// the pointer type from the data layout.
   /// FIXME: The default needs to be removed once all the code is updated.
Index: lib/CodeGen/SafeStack.cpp
===================================================================
--- lib/CodeGen/SafeStack.cpp
+++ lib/CodeGen/SafeStack.cpp
@@ -314,6 +314,11 @@
             continue;
         }
 
+        // FIXME: A more precise solution may consider whether particular types
+        // of intrinsics necessitate moving allocations to the unsafe stack.
+        if (TL->useOnlyLocalStackPointers())
+          return false;
+
         if (const MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I)) {
           if (!IsMemIntrinsicSafe(MI, UI, AllocaPtr, AllocaSize)) {
             DEBUG(dbgs() << "[SafeStack] Unsafe alloca: " << *AllocaPtr
Index: lib/Target/X86/X86ISelLowering.h
===================================================================
--- lib/Target/X86/X86ISelLowering.h
+++ lib/Target/X86/X86ISelLowering.h
@@ -655,6 +655,7 @@
 
     unsigned getJumpTableEncoding() const override;
     bool useSoftFloat() const override;
+    bool useOnlyLocalStackPointers() const override;
 
     MVT getScalarShiftAmountTy(const DataLayout &, EVT) const override {
       return MVT::i8;
Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -1985,6 +1985,10 @@
   return Subtarget.useSoftFloat();
 }
 
+bool X86TargetLowering::useOnlyLocalStackPointers() const {
+  return Subtarget.useSeparateStackSeg();
+}
+
 const MCExpr *
 X86TargetLowering::LowerCustomJumpTableEntry(const MachineJumpTableInfo *MJTI,
                                              const MachineBasicBlock *MBB,
Index: test/Transforms/SafeStack/call.ll
===================================================================
--- test/Transforms/SafeStack/call.ll
+++ test/Transforms/SafeStack/call.ll
@@ -1,5 +1,6 @@
 ; RUN: opt -safe-stack -S -mtriple=i386-pc-linux-gnu < %s -o - | FileCheck %s
 ; RUN: opt -safe-stack -S -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck %s
+; RUN: opt -safe-stack -S -mtriple=i386-pc-linux-gnu -mattr=+separate-stack-seg < %s -o - | FileCheck --check-prefix SEP-STK %s
 
 @.str = private unnamed_addr constant [4 x i8] c"%s\0A\00", align 1
 
@@ -11,6 +12,9 @@
   ; CHECK-LABEL: define void @foo(
   ; CHECK-NOT: __safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @foo(
+  ; SEP-STK-NOT: __safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %a.addr = alloca i8*, align 8
   store i8* %a, i8** %a.addr, align 8
   %0 = load i8*, i8** %a.addr, align 8
@@ -28,6 +32,9 @@
   ; CHECK-LABEL: define void @call_memset
   ; CHECK: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_memset
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %q, i32 0, i32 0
   call void @llvm.memset.p0i8.i64(i8* %arraydecay, i8 1, i64 %len, i32 1, i1 false)
@@ -39,6 +46,9 @@
   ; CHECK-LABEL: define void @call_constant_memset
   ; CHECK-NOT: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_constant_memset
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %q, i32 0, i32 2
   call void @llvm.memset.p0i8.i64(i8* %arraydecay, i8 1, i64 7, i32 1, i1 false)
@@ -50,6 +60,9 @@
   ; CHECK-LABEL: define void @call_constant_overflow_memset
   ; CHECK: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_constant_overflow_memset
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %q, i32 0, i32 7
   call void @llvm.memset.p0i8.i64(i8* %arraydecay, i8 1, i64 5, i32 1, i1 false)
@@ -61,6 +74,9 @@
   ; CHECK-LABEL: define void @call_constant_underflow_memset
   ; CHECK: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_constant_underflow_memset
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr [10 x i8], [10 x i8]* %q, i32 0, i32 -1
   call void @llvm.memset.p0i8.i64(i8* %arraydecay, i8 1, i64 3, i32 1, i1 false)
@@ -73,6 +89,9 @@
   ; CHECK-LABEL: define void @call_readnone
   ; CHECK-NOT: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_readnone
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %q, i32 0, i32 0
   call void @readnone(i8* %arraydecay)
@@ -85,6 +104,9 @@
   ; CHECK-LABEL: define void @call_readnone0_0
   ; CHECK-NOT: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_readnone0_0
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %q, i32 0, i32 0
   call void @readnone0(i8* %arraydecay, i8* zeroinitializer)
@@ -97,6 +119,9 @@
   ; CHECK-LABEL: define void @call_readnone0_1
   ; CHECK: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_readnone0_1
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %q, i32 0, i32 0
   call void @readnone0(i8 *zeroinitializer, i8* %arraydecay)
@@ -109,6 +134,9 @@
   ; CHECK-LABEL: define void @call_readonly
   ; CHECK: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_readonly
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %q, i32 0, i32 0
   call void @readonly(i8* %arraydecay)
@@ -121,6 +149,9 @@
   ; CHECK-LABEL: define void @call_arg_readonly
   ; CHECK: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_arg_readonly
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %q, i32 0, i32 0
   call void @arg_readonly(i8* %arraydecay)
@@ -133,6 +164,9 @@
   ; CHECK-LABEL: define void @call_readwrite
   ; CHECK: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_readwrite
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %q, i32 0, i32 0
   call void @readwrite(i8* %arraydecay)
@@ -145,6 +179,9 @@
   ; CHECK-LABEL: define void @call_capture
   ; CHECK: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_capture
+  ; SEP-STK: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
   %q = alloca [10 x i8], align 1
   %arraydecay = getelementptr inbounds [10 x i8], [10 x i8]* %q, i32 0, i32 0
   call void @capture(i8* %arraydecay)
@@ -156,6 +193,9 @@
   ; CHECK-LABEL: define void @call_lifetime
   ; CHECK-NOT: @__safestack_unsafe_stack_ptr
   ; CHECK: ret void
+  ; SEP-STK-LABEL: define void @call_lifetime
+  ; SEP-STK-NOT: @__safestack_unsafe_stack_ptr
+  ; SEP-STK: ret void
 entry:
   %q = alloca [100 x i8], align 16
   %0 = bitcast [100 x i8]* %q to i8*