Debug info: On ARM ensure that all __TEXT sections come before the

optional DWARF sections, so compiling with -g does not result in
different code being generated for PC-relative loads.

This is reapplying a diet r197922 (__TEXT-only).

llvm-svn: 199681

2 files changed, 25 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
index 0127c488362..965d93c1f4b 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -489,6 +489,13 @@ void ARMAsmPrinter::EmitStartOfAsmFile(Module &M) {
                                    SectionKind::getText());
       OutStreamer.SwitchSection(StaticInitSect);
     }
+
+    // Compiling with debug info should not affect the code
+    // generation.  Ensure the cstring section comes before the
+    // optional __DWARF secion. Otherwise, PC-relative loads would
+    // have to use different instruction sequences at "-g" in order to
+    // reach global data in the same object file.
+    OutStreamer.SwitchSection(getObjFileLowering().getCStringSection());
   }
 
   // Use unified assembler syntax.
diff --git a/llvm/test/DebugInfo/ARM/sectionorder.ll b/llvm/test/DebugInfo/ARM/sectionorder.ll
new file mode 100644
index 00000000000..2e3f3bf9a17
--- /dev/null
+++ b/llvm/test/DebugInfo/ARM/sectionorder.ll
@@ -0,0 +1,18 @@
+; RUN: llc  -filetype=asm %s -o - | FileCheck %s
+
+; Verifies that the DWARF* sections come _after_ the __TEXT sections.
+; rdar://problem/15623193
+
+; CHECK: .section	__TEXT,__text,
+; CHECK-NOT: __DWARF,__debug
+; CHECK: .section	__TEXT,__cstring,cstring_literals
+target triple = "thumbv7-apple-ios"
+
+!llvm.module.flags = !{!3, !4}
+!llvm.dbg.cu = !{!0}
+
+!0 = metadata !{i32 786449, i32 0, i32 12, metadata !"test.c", metadata !"/Volumes/Data/radar/15623193", metadata !"LLVM", i1 true, i1 false, metadata !"", i32 0, metadata !1, metadata !1, metadata !1, metadata !1} ; [ DW_TAG_compile_unit ] [/Volumes/Data/radar/15623193/test.c] [DW_LANG_C99]
+!1 = metadata !{metadata !2}
+!2 = metadata !{i32 0}
+!3 = metadata !{i32 2, metadata !"Dwarf Version", i32 2}
+!4 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}