[SystemZ] Implement backchain attribute (recommit with fix).

This introduces a SystemZ-specific "backchain" attribute on function, which
enables writing the frame backchain link as specified by the ABI.  This will
be used to implement -mbackchain option in clang.

Differential Revision: http://reviews.llvm.org/D19889

Fixed in this version: added RegState::Define and RegState::Kill on R1D
in prologue.

llvm-svn: 268581

1 files changed, 84 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/SystemZ/backchain.ll b/llvm/test/CodeGen/SystemZ/backchain.ll
new file mode 100644
index 00000000000..45775dbf273
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/backchain.ll
@@ -0,0 +1,84 @@
+; Test the backchain attribute.
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
+
+declare i8 *@llvm.stacksave()
+declare void @llvm.stackrestore(i8 *)
+declare void @g()
+
+; nothing should happen if no stack frame is needed.
+define void @f1() "backchain" {
+; CHECK-LABEL: f1:
+; CHECK-NOT: stg
+  ret void
+}
+
+; check that backchain is saved if we call someone
+define void @f2() "backchain" {
+; CHECK-LABEL: f2:
+; CHECK: stmg %r14, %r15, 112(%r15)
+; CHECK: lgr %r1, %r15
+; CHECK: aghi %r15, -160
+; CHECK: stg %r1, 0(%r15)
+  call void @g()
+  call void @g()
+  ret void
+}
+
+; check that backchain is saved if we have an alloca
+define void @f3() "backchain" {
+; CHECK-LABEL: f3:
+; CHECK-NOT: stmg
+; CHECK: lgr %r1, %r15
+; CHECK: aghi %r15, -168
+; CHECK: stg %r1, 0(%r15)
+  %ign = alloca i8, i32 4
+  ret void
+}
+
+; check that alloca copies the backchain
+define void @f4(i32 %len) "backchain" {
+; CHECK-LABEL: f4:
+; CHECK: stmg %r11, %r15, 88(%r15)
+; CHECK: lgr %r1, %r15
+; CHECK: aghi %r15, -160
+; CHECK: stg %r1, 0(%r15)
+; CHECK: lgr %r11, %r15
+; CHECK: lg [[BC:%r[0-9]+]], 0(%r15)
+; CHECK: lgr [[NEWSP:%r[0-9]+]], %r15
+; CHECK: lgr %r15, [[NEWSP]]
+; CHECK: stg [[BC]], 0([[NEWSP]])
+  %ign = alloca i8, i32 %len
+  ret void
+}
+
+; check that llvm.stackrestore restores the backchain
+define void @f5(i32 %count1, i32 %count2) "backchain" {
+; CHECK-LABEL: f5:
+; CHECK: stmg %r11, %r15, 88(%r15)
+; CHECK: lgr %r1, %r15
+; CHECK: aghi %r15, -160
+; CHECK: stg %r1, 0(%r15)
+; CHECK: lgr %r11, %r15
+; CHECK: lgr [[SAVESP:%r[0-9]+]], %r15
+; CHECK: lg [[BC:%r[0-9]+]], 0(%r15)
+; CHECK: lgr [[NEWSP:%r[0-9]+]], %r15
+; CHECK: lgr %r15, [[NEWSP]]
+; CHECK: stg [[BC]], 0([[NEWSP]])
+; CHECK: lg [[BC2:%r[0-9]+]], 0(%r15)
+; CHECK: lgr %r15, [[SAVESP]]
+; CHECK: stg [[BC2]], 0([[SAVESP]])
+; CHECK: lg [[BC3:%r[0-9]+]], 0(%r15)
+; CHECK: lgr [[NEWSP2:%r[0-9]+]], %r15
+; CHECK: lgr %r15, [[NEWSP2]]
+; CHECK: stg [[BC3]], 0([[NEWSP2]])
+; CHECK: lmg %r11, %r15, 248(%r11)
+; CHECK: br %r14
+  %src = call i8 *@llvm.stacksave()
+  %array1 = alloca i8, i32 %count1
+  store volatile i8 0, i8 *%array1
+  call void @llvm.stackrestore(i8 *%src)
+  %array2 = alloca i8, i32 %count2
+  store volatile i8 0, i8 *%array2
+  ret void
+}