Fix epilogue codegen to avoid leaving the stack pointer in an invalid

state. Previously Thumb2 would restore sp from fp like this:
mov sp, r7
sub, sp, #4
If an interrupt is taken after the 'mov' but before the 'sub', callee-saved
registers might be clobbered by the interrupt handler. Instead, try
restoring directly from sp:
add sp, #4
Or, if necessary (with VLA, etc.) use a scratch register to compute sp and
then restore it:
sub.w r4, r7, #8
mov sp, r7
rdar://8465407


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119977 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 4 deletions

diff --git a/test/CodeGen/Thumb/dyn-stackalloc.ll b/test/CodeGen/Thumb/dyn-stackalloc.ll
index 5c8ad974bc..1f31dca052 100644
--- a/test/CodeGen/Thumb/dyn-stackalloc.ll
+++ b/test/CodeGen/Thumb/dyn-stackalloc.ll
@@ -1,12 +1,15 @@
-; RUN: llc < %s -march=thumb | not grep {ldr sp}
-; RUN: llc < %s -mtriple=thumb-apple-darwin | \
-; RUN:   not grep {sub.*r7}
-; RUN: llc < %s -march=thumb | grep {mov.*r6, sp}
+; RUN: llc < %s -mtriple=thumb-apple-darwin | FileCheck %s
 
 	%struct.state = type { i32, %struct.info*, float**, i32, i32, i32, i32, i32, i32, i32, i32, i32, i64, i64, i64, i64, i64, i64, i8* }
 	%struct.info = type { i32, i32, i32, i32, i32, i32, i32, i8* }
 
 define void @t1(%struct.state* %v) {
+; CHECK: t1:
+; CHECK: push
+; CHECK: add r7, sp, #12
+; CHECK: mov r2, sp
+; CHECK: subs r4, r2, r1
+; CHECK: mov sp, r4
 	%tmp6 = load i32* null
 	%tmp8 = alloca float, i32 %tmp6
 	store i32 1, i32* null
@@ -34,6 +37,18 @@ declare fastcc void @f2(float*, float*, float*, i32)
 @str215 = external global [2 x i8]
 
 define void @t2(%struct.comment* %vc, i8* %tag, i8* %contents) {
+; CHECK: t2:
+; CHECK: push
+; CHECK: add r7, sp, #12
+; CHECK: sub sp, #8
+; CHECK: mov r6, sp
+; CHECK: str r2, [r6, #4]
+; CHECK: str r0, [r6]
+; CHECK-NOT: ldr r0, [sp
+; CHECK: ldr r0, [r6, #4]
+; CHECK: mov r0, sp
+; CHECK: subs r5, r0, r1
+; CHECK: mov sp, r5
 	%tmp1 = call i32 @strlen( i8* %tag )
 	%tmp3 = call i32 @strlen( i8* %contents )
 	%tmp4 = add i32 %tmp1, 2