AArch64: Implement support for the shadowcallstack attribute.

The implementation of shadow call stack on aarch64 is quite different to
the implementation on x86_64. Instead of reserving a segment register for
the shadow call stack, we reserve the platform register, x18. Any function
that spills lr to sp also spills it to the shadow call stack, a pointer to
which is stored in x18.

Differential Revision: https://reviews.llvm.org/D45239

llvm-svn: 329236

1 files changed, 47 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/AArch64/shadow-call-stack.ll b/llvm/test/CodeGen/AArch64/shadow-call-stack.ll
new file mode 100644
index 00000000000..dbd44fd3cd1
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/shadow-call-stack.ll
@@ -0,0 +1,47 @@
+; RUN: llc -verify-machineinstrs -o - %s -mtriple=aarch64-linux-gnu -mattr=+reserve-x18 | FileCheck %s
+
+define void @f1() shadowcallstack {
+  ; CHECK: f1:
+  ; CHECK-NOT: x18
+  ; CHECK: ret
+  ret void
+}
+
+declare void @foo()
+
+define void @f2() shadowcallstack {
+  ; CHECK: f2:
+  ; CHECK-NOT: x18
+  ; CHECK: b foo
+  tail call void @foo()
+  ret void
+}
+
+declare i32 @bar()
+
+define i32 @f3() shadowcallstack {
+  ; CHECK: f3:
+  ; CHECK: str x30, [x18], #8
+  ; CHECK: str x30, [sp, #-16]!
+  %res = call i32 @bar()
+  %res1 = add i32 %res, 1
+  ; CHECK: ldr x30, [sp], #16
+  ; CHECK: ldr x30, [x18, #-8]!
+  ; CHECK: ret
+  ret i32 %res
+}
+
+define i32 @f4() shadowcallstack {
+  ; CHECK: f4:
+  %res1 = call i32 @bar()
+  %res2 = call i32 @bar()
+  %res3 = call i32 @bar()
+  %res4 = call i32 @bar()
+  %res12 = add i32 %res1, %res2
+  %res34 = add i32 %res3, %res4
+  %res1234 = add i32 %res12, %res34
+  ; CHECK: ldp {{.*}}x30, [sp
+  ; CHECK: ldr x30, [x18, #-8]!
+  ; CHECK: ret
+  ret i32 %res1234
+}