Remove incorrectly implemented -mibt-seal

The option from D116070 does not work as intended and will not be needed when
hidden visibility is used. A function needs ENDBR if it may be reached
indirectly. If we make ThinLTO combine the address-taken property (close to
`!GV.use_empty() && !GV.hasAtLeastLocalUnnamedAddr()`), then the condition can
be expressed with:

`AddressTaken || (!F.hasLocalLinkage() && (VisibleToRegularObj || !F.hasHiddenVisibility()))`

The current `F.hasAddressTaken()` condition does not take into acount of
address-significance in another bitcode file or ELF relocatable file.

For the Linux kernel, it uses relocatable linking. lld/ELF uses a
conservative approach by setting all `VisibleToRegularObj` to true.
Using the non-relocatable semantics may under-estimate
`VisibleToRegularObj`. As @pcc mentioned on
https://github.com/ClangBuiltLinux/linux/issues/1737#issuecomment-1343414686
, we probably need a symbol list to supply additional
`VisibleToRegularObj` symbols (not part of the relocatable LTO link).

Reviewed By: samitolvanen

Differential Revision: https://reviews.llvm.org/D140363

1 files changed, 0 insertions, 6 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index d89a80e..1cabf28 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1495,9 +1495,6 @@ void CompilerInvocation::GenerateCodeGenArgs(
   else if (Opts.CFProtectionBranch)
     GenerateArg(Args, OPT_fcf_protection_EQ, "branch", SA);
 
-  if (Opts.IBTSeal)
-    GenerateArg(Args, OPT_mibt_seal, SA);
-
   if (Opts.FunctionReturnThunks)
     GenerateArg(Args, OPT_mfunction_return_EQ, "thunk-extern", SA);
 
@@ -1857,9 +1854,6 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args,
       Opts.FunctionReturnThunks = static_cast<unsigned>(Val);
   }
 
-  if (Opts.PrepareForLTO && Args.hasArg(OPT_mibt_seal))
-    Opts.IBTSeal = 1;
-
   for (auto *A :
        Args.filtered(OPT_mlink_bitcode_file, OPT_mlink_builtin_bitcode)) {
     CodeGenOptions::BitcodeFileToLink F;