[XCOFF][AIX] Use unique section names for LSDA and EH info sections with -ffunction-sections

Summary:
When -ffunction-sections is on, this patch makes the compiler to generate unique LSDA and EH info sections for functions on AIX by appending the function name to the section name as a suffix. This will allow the AIX linker to garbage-collect unused function.

Reviewed by: MaskRay, hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D124855

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 3246d77..d34ba6f 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -2565,6 +2565,20 @@ MCSection *TargetLoweringObjectFileXCOFF::getSectionForTOCEntry(
           XCOFF::XTY_SD));
 }
 
+MCSection *TargetLoweringObjectFileXCOFF::getSectionForLSDA(
+    const Function &F, const MCSymbol &FnSym, const TargetMachine &TM) const {
+  auto *LSDA = cast<MCSectionXCOFF>(LSDASection);
+  if (TM.getFunctionSections()) {
+    // If option -ffunction-sections is on, append the function name to the
+    // name of the LSDA csect so that each function has its own LSDA csect.
+    // This helps the linker to garbage-collect EH info of unused functions.
+    SmallString<128> NameStr = LSDA->getName();
+    raw_svector_ostream(NameStr) << '.' << F.getName();
+    LSDA = getContext().getXCOFFSection(NameStr, LSDA->getKind(),
+                                        LSDA->getCsectProp());
+  }
+  return LSDA;
+}
 //===----------------------------------------------------------------------===//
 //                                  GOFF
 //===----------------------------------------------------------------------===//