maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

Write only minimal .debug_line information. 

Summary:
We used to output .debug_line information for every instruction, but because of the way
gdb (and probably lldb as of llvm::DWARFDebugLine::LineTable::findAddress) queries the
line table it's not necessary to output information for two instructions if they follow
each other and map to the same source line. By not repeating this information we generate
a bit less .debug_line data.

(cherry picked from FBD3056402)
This commit is contained in:
Gabriel Poesia 2016-03-15 16:22:04 -07:00 committed by Maksim Panchenko
parent a60914427c
commit 9cdb7bdb55
1 changed files with 8 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
bolt/RewriteInstance.cpp
View File

@ -1077,6 +1077,11 @@ void emitFunction(MCStreamer &Streamer, BinaryFunction &Function,
if (opts::AlignBlocks && BB->getAlignment() > 1)
Streamer.EmitCodeAlignment(BB->getAlignment());
Streamer.EmitLabel(BB->getLabel());
// Remember last .debug_line entry emitted so that we don't repeat them in
// subsequent instructions, as gdb can figure it out by looking at the
// previous instruction with available line number info.
SMLoc LastLocSeen;
for (const auto &Instr : *BB) {
// Handle pseudo instructions.
if (BC.MIA->isEHLabel(Instr)) {
@ -1090,7 +1095,8 @@ void emitFunction(MCStreamer &Streamer, BinaryFunction &Function,
if (!BC.MIA->isCFI(Instr)) {
if (opts::UpdateDebugSections) {
auto RowReference = DebugLineTableRowRef::fromSMLoc(Instr.getLoc());
if (RowReference != DebugLineTableRowRef::NULL_ROW) {
if (RowReference != DebugLineTableRowRef::NULL_ROW &&
Instr.getLoc().getPointer() != LastLocSeen.getPointer()) {
auto CompileUnit =
BC.OffsetToDwarfCU[RowReference.DwCompileUnitIndex];
assert(CompileUnit &&
@ -1113,6 +1119,7 @@ void emitFunction(MCStreamer &Streamer, BinaryFunction &Function,
OriginalRow.Isa,
OriginalRow.Discriminator);
BC.Ctx->setDwarfCompileUnitID(CompileUnit->getOffset());
LastLocSeen = Instr.getLoc();
}
}