[MC/DWARF] Generate multiple .debug_line entries for adjacent .loc directives

The compiler occasionally generates multiple .loc directives in a row
(at the same instruction address).  These need to be transformed into
multple actual .debug_line table entries, since they are used to signal
certain information to the debugger (e.g. if the opening brace of a
function body is on the same line as the declaration).

The MCAsmStreamer version of EmitDwarfLocDirective handles this
correctly by emitting a .loc directive every time it is called.
However, the MCObjectStream version simply defaults to recording
the information and emitting only a single table entry later,
e.g. when EmitInstruction is called.

This patch introduces a MCAsmStreamer::EmitDwarfLocDirective
version that emits a line table entry for a .loc directive
that may already be pending before recording the new directive.
(This is similar to how this is handled in GNU as.)

With this patch (and the code alignment factor patch) applied,
I'm now getting identical DWARF .debug sections for all test-suite
object files on PowerPC for the internal and the external assembler.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184357 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 0 deletions

diff --git a/lib/MC/MCObjectStreamer.cpp b/lib/MC/MCObjectStreamer.cpp
index 2d7657c591..a1ed01cebc 100644
--- a/lib/MC/MCObjectStreamer.cpp
+++ b/lib/MC/MCObjectStreamer.cpp
@@ -259,6 +259,19 @@ void MCObjectStreamer::EmitBundleUnlock() {
   llvm_unreachable(BundlingNotImplementedMsg);
 }
 
+void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
+                                             unsigned Column, unsigned Flags,
+                                             unsigned Isa,
+                                             unsigned Discriminator,
+                                             StringRef FileName) {
+  // In case we see two .loc directives in a row, make sure the
+  // first one gets a line entry.
+  MCLineEntry::Make(this, getCurrentSection().first);
+
+  this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
+                                          Isa, Discriminator, FileName);
+}
+
 void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
                                                 const MCSymbol *LastLabel,
                                                 const MCSymbol *Label,