[BPF] Do not generate BTF sections unnecessarily

If There is no types/non-empty strings, do not generate
.BTF section. If there is no func_info/line_info, do
not generate .BTF.ext section.

Signed-off-by: Yonghong Song <yhs@fb.com>

Differential Revision: https://reviews.llvm.org/D58936

llvm-svn: 355360

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Target/BPF/BTFDebug.cpp b/llvm/lib/Target/BPF/BTFDebug.cpp
index ca3a8c5740e..3f5531357a9 100644
--- a/llvm/lib/Target/BPF/BTFDebug.cpp
+++ b/llvm/lib/Target/BPF/BTFDebug.cpp
@@ -546,6 +546,10 @@ void BTFDebug::emitCommonHeader() {
 }
 
 void BTFDebug::emitBTFSection() {
+  // Do not emit section if no types and only "" string.
+  if (!TypeEntries.size() && StringTable.getSize() == 1)
+    return;
+
   MCContext &Ctx = OS.getContext();
   OS.SwitchSection(Ctx.getELFSection(".BTF", ELF::SHT_PROGBITS, 0));
 
@@ -578,6 +582,10 @@ void BTFDebug::emitBTFSection() {
 }
 
 void BTFDebug::emitBTFExtSection() {
+  // Do not emit section if empty FuncInfoTable and LineInfoTable.
+  if (!FuncInfoTable.size() && !LineInfoTable.size())
+    return;
+
   MCContext &Ctx = OS.getContext();
   OS.SwitchSection(Ctx.getELFSection(".BTF.ext", ELF::SHT_PROGBITS, 0));