[CXX TLS calling convention] Add CXX TLS calling convention.

This commit adds a new target-independent calling convention for C++ TLS
access functions. It aims to minimize overhead in the caller by perserving as
many registers as possible.

The target-specific implementation for X86-64 is defined as following:
  Arguments are passed as for the default C calling convention
  The same applies for the return value(s)
  The callee preserves all GPRs - except RAX and RDI

The access function makes C-style TLS function calls in the entry and exit
block, C-style TLS functions save a lot more registers than normal calls.
The added calling convention ties into the existing implementation of the
C-style TLS functions, so we can't simply use existing calling conventions
such as preserve_mostcc.

rdar://9001553

llvm-svn: 254737

1 files changed, 71 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/cxx_tlscc64.ll b/llvm/test/CodeGen/X86/cxx_tlscc64.ll
new file mode 100644
index 00000000000..c229521cc9a
--- /dev/null
+++ b/llvm/test/CodeGen/X86/cxx_tlscc64.ll
@@ -0,0 +1,71 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-apple-darwin -enable-shrink-wrap=true | FileCheck --check-prefix=SHRINK %s
+%struct.S = type { i8 }
+
+@sg = internal thread_local global %struct.S zeroinitializer, align 1
+@__dso_handle = external global i8
+@__tls_guard = internal thread_local unnamed_addr global i1 false
+
+declare void @_ZN1SC1Ev(%struct.S*)
+declare void @_ZN1SD1Ev(%struct.S*)
+declare i32 @_tlv_atexit(void (i8*)*, i8*, i8*)
+
+; Every GPR should be saved - except rdi, rax, and rsp
+; CHECK-LABEL: _ZTW2sg
+; CHECK: pushq %r11
+; CHECK: pushq %r10
+; CHECK: pushq %r9
+; CHECK: pushq %r8
+; CHECK: pushq %rsi
+; CHECK: pushq %rdx
+; CHECK: pushq %rcx
+; CHECK: pushq %rbx
+; CHECK: callq
+; CHECK: jne
+; CHECK: callq
+; CHECK: tlv_atexit
+; CHECK: callq
+; CHECK: popq %rbx
+; CHECK: popq %rcx
+; CHECK: popq %rdx
+; CHECK: popq %rsi
+; CHECK: popq %r8
+; CHECK: popq %r9
+; CHECK: popq %r10
+; CHECK: popq %r11
+; SHRINK-LABEL: _ZTW2sg
+; SHRINK: callq
+; SHRINK: jne
+; SHRINK: pushq %r11
+; SHRINK: pushq %r10
+; SHRINK: pushq %r9
+; SHRINK: pushq %r8
+; SHRINK: pushq %rsi
+; SHRINK: pushq %rdx
+; SHRINK: pushq %rcx
+; SHRINK: pushq %rbx
+; SHRINK: callq
+; SHRINK: tlv_atexit
+; SHRINK: popq %rbx
+; SHRINK: popq %rcx
+; SHRINK: popq %rdx
+; SHRINK: popq %rsi
+; SHRINK: popq %r8
+; SHRINK: popq %r9
+; SHRINK: popq %r10
+; SHRINK: popq %r11
+; SHRINK: LBB{{.*}}:
+; SHRINK: callq
+define cxx_fast_tlscc nonnull %struct.S* @_ZTW2sg() {
+  %.b.i = load i1, i1* @__tls_guard, align 1
+  br i1 %.b.i, label %__tls_init.exit, label %init.i
+
+init.i:
+  store i1 true, i1* @__tls_guard, align 1
+  tail call void @_ZN1SC1Ev(%struct.S* nonnull @sg) #2
+  %1 = tail call i32 @_tlv_atexit(void (i8*)* nonnull bitcast (void (%struct.S*)* @_ZN1SD1Ev to void (i8*)*), i8* nonnull getelementptr inbounds (%struct.S, %struct.S* @sg, i64 0, i32 0), i8* nonnull @__dso_handle) #2
+  br label %__tls_init.exit
+
+__tls_init.exit:
+  ret %struct.S* @sg
+}