ARM: Add support for segmented stacks

Patch by Alex Crichton, ILyoan, Luqman Aden and Svetoslav.

llvm-svn: 205430
diff --git a/llvm/test/CodeGen/Thumb2/segmented-stacks.ll b/llvm/test/CodeGen/Thumb2/segmented-stacks.ll
new file mode 100644
index 0000000..602fc84
--- /dev/null
+++ b/llvm/test/CodeGen/Thumb2/segmented-stacks.ll
@@ -0,0 +1,32 @@
+; RUN: llc < %s -mtriple=thumb-linux-androideabi -march=thumb -mcpu=arm1156t2-s -mattr=+thumb2 -segmented-stacks -verify-machineinstrs | FileCheck %s -check-prefix=Thumb-android
+; RUN: llc < %s -mtriple=thumb-linux-androideabi -march=thumb -mcpu=arm1156t2-s -mattr=+thumb2 -segmented-stacks -filetype=obj
+
+
+; Just to prevent the alloca from being optimized away
+declare void @dummy_use(i32*, i32)
+
+define void @test_basic() {
+        %mem = alloca i32, i32 10
+        call void @dummy_use (i32* %mem, i32 10)
+	ret void
+
+; Thumb-android:      test_basic:
+
+; Thumb-android:      push    {r4, r5}
+; Thumb-android-NEXT: mrc     p15, #0, r4, c13, c0, #3
+; Thumb-android-NEXT: mov     r5, sp
+; Thumb-android-NEXT: ldr     r4, [r4, #252]
+; Thumb-android-NEXT: cmp     r4, r5
+; Thumb-android-NEXT: blo     .LBB0_2
+
+; Thumb-android:      mov     r4, #48
+; Thumb-android-NEXT: mov     r5, #0
+; Thumb-android-NEXT: push    {lr}
+; Thumb-android-NEXT: bl      __morestack
+; Thumb-android-NEXT: ldr     lr, [sp], #4
+; Thumb-android-NEXT: pop     {r4, r5}
+; Thumb-android-NEXT: bx      lr
+
+; Thumb-android:      pop     {r4, r5}
+
+}