Fix PR18743.

The IR
@foo = private constant i32 42

is valid, but before this patch we would produce an invalid MachO from it. It
was invalid because it would use an L label in a section where the liker needs
the labels in order to atomize it.

One way of fixing it would be to just reject this IR in the backend, but that
would not be very front end friendly.

What this patch does is use an 'l' prefix in sections that we know the linker
requires symbols for atomizing them. This allows frontends to just use
private and not worry about which sections they go to or how the linker handles
them.

One small issue with this strategy is that now a symbol name depends on the
section, which is not available before codegen. This is not a problem in
practice. The reason is that it only happens with private linkage, which will
be ignored by the non codegen users (llvm-nm and llvm-ar).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201608 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 71 insertions, 0 deletions

diff --git a/test/CodeGen/X86/osx-private-labels.ll b/test/CodeGen/X86/osx-private-labels.ll
new file mode 100644
index 0000000000..349ce7d0cc
--- /dev/null
+++ b/test/CodeGen/X86/osx-private-labels.ll
@@ -0,0 +1,71 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
+; Test all the cases where a L label is safe. Removing any entry from
+; TargetLoweringObjectFileMachO::isSectionAtomizableBySymbols should cause
+; this to fail.
+; We also test some noteworthy cases that require an l label.
+
+@private1 = private unnamed_addr constant [4 x i8] c"zed\00"
+; CHECK: .section	__TEXT,__cstring,cstring_literals
+; CHECK-NEXT: L_private1:
+
+@private2 = private unnamed_addr constant [5 x i16] [i16 116, i16 101,
+                                                     i16 115, i16 116, i16 0]
+; CHECK: .section	__TEXT,__ustring
+; CHECK-NEXT: .align	1
+; CHECK-NEXT: l_private2:
+
+; There is no dedicated 4 byte strings on MachO.
+
+%struct.NSConstantString = type { i32*, i32, i8*, i32 }
+@private3 = private constant %struct.NSConstantString { i32* null, i32 1992, i8* null, i32 0 }, section "__DATA,__cfstring"
+; CHECK: .section	__DATA,__cfstring
+; CHECK-NEXT: .align	4
+; CHECK-NEXT: L_private3:
+
+; There is no dedicated 1 or 2 byte constant section on MachO.
+
+@private4 = private unnamed_addr constant i32 42
+; CHECK: .section	__TEXT,__literal4,4byte_literals
+; CHECK-NEXT: .align	2
+; CHECK-NEXT: L_private4:
+
+@private5 = private unnamed_addr constant i64 42
+; CHECK: .section	__TEXT,__literal8,8byte_literals
+; CHECK-NEXT: .align	3
+; CHECK-NEXT: L_private5:
+
+@private6 = private unnamed_addr constant i128 42
+; CHECK: .section	__TEXT,__literal16,16byte_literals
+; CHECK-NEXT: .align	3
+; CHECK-NEXT: L_private6:
+
+%struct._objc_class = type { i8* }
+@private7 = private global %struct._objc_class* null, section "__OBJC,__cls_refs,literal_pointers,no_dead_strip"
+; CHECK: .section	__OBJC,__cls_refs,literal_pointers,no_dead_strip
+; CHECK: .align	3
+; CHECK: L_private7:
+
+@private8 = private global i32* null, section "__DATA,__nl_symbol_ptr,non_lazy_symbol_pointers"
+; CHECK: .section	__DATA,__nl_symbol_ptr,non_lazy_symbol_pointers
+; CHECK-NEXT: .align	3
+; CHECK-NEXT: L_private8:
+
+@private9 = private global i32* null, section "__DATA,__la_symbol_ptr,lazy_symbol_pointers"
+; CHECK: .section	__DATA,__la_symbol_ptr,lazy_symbol_pointers
+; CHECK-NEXT: .align	3
+; CHECK-NEXT: L_private9:
+
+@private10 = private global i32* null, section "__DATA,__mod_init_func,mod_init_funcs"
+; CHECK: .section	__DATA,__mod_init_func,mod_init_funcs
+; CHECK-NEXT: .align	3
+; CHECK-NEXT: L_private10:
+
+@private11 = private global i32* null, section "__DATA,__mod_term_func,mod_term_funcs"
+; CHECK: .section	__DATA,__mod_term_func,mod_term_funcs
+; CHECK-NEXT: .align	3
+; CHECK-NEXT: L_private11:
+
+@private12 = private global i32* null, section "__DATA,__foobar,interposing"
+; CHECK: .section	__DATA,__foobar,interposing
+; CHECK-NEXT: .align	3
+; CHECK-NEXT: L_private12: