Index: llvm/lib/Target/ARM/ARMSubtarget.cpp
===================================================================
--- llvm/lib/Target/ARM/ARMSubtarget.cpp
+++ llvm/lib/Target/ARM/ARMSubtarget.cpp
@@ -235,9 +235,12 @@
   if (isTargetMachO() && isTargetIOS() && getTargetTriple().isOSVersionLT(5, 0))
     SupportsTailCall = false;
 
+  // Multi-instruction IT Blocks have been deprecated in ARMv8, additionally
+  // Windows does not permit them, even for older ARM versions.
+
   switch (IT) {
   case DefaultIT:
-    RestrictIT = hasV8Ops() && !hasMinSize();
+    RestrictIT = (hasV8Ops() && !hasMinSize()) || isTargetWindows();
     break;
   case RestrictedIT:
     RestrictIT = true;
Index: llvm/test/CodeGen/ARM/restrict-it-minsize.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/ARM/restrict-it-minsize.ll
@@ -0,0 +1,29 @@
+; RUN: llc < %s -mtriple=thumbv7-linux-gnueabihf | FileCheck %s
+; RUN: llc < %s -mtriple=thumbv8-linux-gnueabihf | FileCheck %s
+; RUN: llc < %s -mtriple=thumbv7-pc-windows-msvc | FileCheck %s --check-prefix=CHECK-RESTRICTIT
+; RUN: llc < %s -mtriple=thumbv8-pc-windows-msvc | FileCheck %s --check-prefix=CHECK-RESTRICTIT
+
+; Verifies that IT blocks are unrestricted when optimizing for size, except on Windows.
+
+define i32 @bundled_instruction(i32* %addr, i32** %addr2, i1 %tst) minsize optsize {
+; CHECK-LABEL: bundled_instruction:
+; CHECK: itee ne
+; CHECK: movne	r0, #0
+; CHECK: ldmeq r3!, {r0}
+; CHECK: streq r3, [r1]
+; CHECK-RESTRICTIT: beq     {{.+}}0_2
+; CHECK-RESTRICTIT:  movs    r0, #0
+; CHECK-RESTRICTIT: {{.+}}0_2:
+; CHECK-RESTRICTIT: ldm r3!, {r0}
+; CHECK-RESTRICTIT: str r3, [r1]
+  br i1 %tst, label %true, label %false
+
+true:
+  ret i32 0
+
+false:
+  %res = load i32, i32* %addr, align 4
+  %next = getelementptr i32, i32* %addr, i32 1
+  store i32* %next, i32** %addr2
+  ret i32 %res
+}
Index: llvm/test/CodeGen/ARM/restrict-it.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/ARM/restrict-it.ll
@@ -0,0 +1,29 @@
+; RUN: llc < %s -mtriple=thumbv7-linux-gnueabihf | FileCheck %s
+; RUN: llc < %s -mtriple=thumbv8-linux-gnueabihf | FileCheck %s --check-prefix=CHECK-RESTRICTIT
+; RUN: llc < %s -mtriple=thumbv7-pc-windows-msvc | FileCheck %s --check-prefix=CHECK-RESTRICTIT
+; RUN: llc < %s -mtriple=thumbv8-pc-windows-msvc | FileCheck %s --check-prefix=CHECK-RESTRICTIT
+
+; Verifies that restricted IT blocks are enabled for v8, and always on Windows.
+
+define i32 @bundled_instruction(i32* %addr, i32** %addr2, i1 %tst) {
+; CHECK-LABEL: bundled_instruction:
+; CHECK: itee ne
+; CHECK: movne	r0, #0
+; CHECK: ldreq	r0, [r3], #4
+; CHECK: streq	r3, [r1]
+; CHECK-RESTRICTIT: beq     {{.+}}0_2
+; CHECK-RESTRICTIT:  movs    r0, #0
+; CHECK-RESTRICTIT: {{.+}}0_2:
+; CHECK-RESTRICTIT: ldr     r0, [r3], #4
+; CHECK-RESTRICTIT: str     r3, [r1]
+  br i1 %tst, label %true, label %false
+
+true:
+  ret i32 0
+
+false:
+  %res = load i32, i32* %addr, align 4
+  %next = getelementptr i32, i32* %addr, i32 1
+  store i32* %next, i32** %addr2
+  ret i32 %res
+}