[SystemZ] [SSP] Add support for LOAD_STACK_GUARD.

This fixes PR22248 on s390x.  The previous attempt at this was D19101,
which was before LOAD_STACK_GUARD existed.  Compared to the previous
version, this always emits a rather ugly block of 4 instructions, involving
a thread pointer load that can't be shared with other potential users.
However, this is necessary for SSP - spilling the guard value (or thread
pointer used to load it) is counter to the goal, since it could be
overwritten along with the frame it protects.

Differential Revision: http://reviews.llvm.org/D19363

llvm-svn: 267340

1 files changed, 35 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/SystemZ/stack-guard.ll b/llvm/test/CodeGen/SystemZ/stack-guard.ll
new file mode 100644
index 00000000000..0889e7ba941
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/stack-guard.ll
@@ -0,0 +1,35 @@
+; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
+
+; CHECK-LABEL: @test_stack_guard
+; CHECK: ear [[REG1:%r[1-9][0-9]?]], %a0
+; CHECK: sllg [[REG1]], [[REG1]], 32
+; CHECK: ear [[REG1]], %a1
+; CHECK: lg [[REG1]], 40([[REG1]])
+; CHECK: stg [[REG1]], {{[0-9]*}}(%r15)
+; CHECK: brasl %r14, foo3@PLT
+; CHECK: ear [[REG2:%r[1-9][0-9]?]], %a0
+; CHECK: sllg [[REG2]], [[REG2]], 32
+; CHECK: ear [[REG2]], %a1
+; CHECK: lg [[REG2]], 40([[REG2]])
+; CHECK: sg [[REG2]], {{[0-9]*}}(%r15)
+
+define i32 @test_stack_guard() #0 {
+entry:
+  %a1 = alloca [256 x i32], align 4
+  %0 = bitcast [256 x i32]* %a1 to i8*
+  call void @llvm.lifetime.start(i64 1024, i8* %0)
+  %arraydecay = getelementptr inbounds [256 x i32], [256 x i32]* %a1, i64 0, i64 0
+  call void @foo3(i32* %arraydecay)
+  call void @llvm.lifetime.end(i64 1024, i8* %0)
+  ret i32 0
+}
+
+; Function Attrs: nounwind
+declare void @llvm.lifetime.start(i64, i8* nocapture)
+
+declare void @foo3(i32*)
+
+; Function Attrs: nounwind
+declare void @llvm.lifetime.end(i64, i8* nocapture)
+
+attributes #0 = { sspstrong }