1 files changed, 37 insertions, 0 deletions
diff --git a/test/CodeGen/X86/tls-addr-non-leaf-function.ll b/test/CodeGen/X86/tls-addr-non-leaf-function.ll
new file mode 100644
index 0000000..ec47232
--- /dev/null
+++ b/test/CodeGen/X86/tls-addr-non-leaf-function.ll
@@ -0,0 +1,37 @@
+; RUN: llc < %s -relocation-model=pic -O2 -disable-fp-elim -o - | FileCheck %s
+; RUN: llc < %s -relocation-model=pic -O2 -o - | FileCheck %s
+
+; This test runs twice with different options regarding the frame pointer:
+; first the elimination is disabled, then it is enabled. The disabled case is
+; the "control group".
+; The function 'foo' below is marked with the "no-frame-pointer-elim-non-leaf"
+; attribute which dictates that the frame pointer should not be eliminated
+; unless the function is a leaf (i.e. it doesn't call any other function).
+; Now, 'foo' is not a leaf function, because it performs a TLS access which on
+; X86 ELF in PIC mode is expanded as a library call.
+; This call is represented with a pseudo-instruction which doesn't appear to be
+; a call when inspected by the analysis passes (it doesn't have the "isCall"
+; flag), and the ISel lowering code creating the pseudo was not informing the 
+; MachineFrameInfo that the function contained calls. This affected the decision
+; whether to eliminate the frame pointer.
+; With the fix, the "hasCalls" flag is set in the MFI for the function whenever
+; a TLS access pseudo-instruction is created, so 'foo' appears to be a non-leaf
+; function, and the difference in the options does not affect codegen: both
+; versions will have a frame pointer.
+
+; Test that there's some frame pointer usage in 'foo'...
+; CHECK: foo:
+; CHECK: pushq %rbp
+; CHECK: movq %rsp, %rbp
+; ... and the TLS library call is also present.
+; CHECK: leaq x@TLSGD(%rip), %rdi
+; CHECK: callq __tls_get_addr@PLT
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@x = thread_local global i32 0
+define i32 @foo() "no-frame-pointer-elim-non-leaf" {
+  %a = load i32* @x, align 4
+  ret i32 %a
+}