[ELF][ARM] Redesign of .ARM.exidx handling to use a SyntheticSection

Instead of creating extra Synthetic .ARM.exidx sections to account for
gaps in the table, create a single .ARM.exidx SyntheticSection that can
derive the contents of the gaps from a sorted list of the executable
InputSections. This has the benefit of moving the ARM specific code for
SyntheticSections in SHF_LINK_ORDER processing and the table merging code
into the ARM specific SyntheticSection. This also makes it easier to create
EXIDX_CANTUNWIND table entries for executable InputSections that don't
have an associated .ARM.exidx section.

Fixes pr40277

Differential Revision: https://reviews.llvm.org/D59216

llvm-svn: 356666

1 files changed, 3 insertions, 1 deletions

diff --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index a7f35ebfc57..4cb5a3cdc59 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -289,7 +289,9 @@ void OutputSection::finalize() {
     // SHF_LINK_ORDER flag. The dependency is indicated by the sh_link field. We
     // need to translate the InputSection sh_link to the OutputSection sh_link,
     // all InputSections in the OutputSection have the same dependency.
-    if (auto *D = First->getLinkOrderDep())
+    if (auto *EX = dyn_cast<ARMExidxSyntheticSection>(First))
+      Link = EX->getLinkOrderDep()->getParent()->SectionIndex;
+    else if (auto *D = First->getLinkOrderDep())
       Link = D->getParent()->SectionIndex;
   }