pcc accepted this revision.
pcc added a comment.
This revision is now accepted and ready to land.
LGTM
================
Comment at: include/clang/Basic/CodeGenOptions.def:120
+CODEGENOPT(EnableSplitLTOUnit, 1, 0) ///< Enable LTO unit splitting to support
+ /// CFI and tranditional whole program
+ /// devirtulization that require whole
----------------
traditional
================
Comment at: include/clang/Basic/CodeGenOptions.def:121
+ /// CFI and tranditional whole program
+ /// devirtulization that require whole
+ /// program IR support.
----------------
devirtualization
================
Comment at: lib/Driver/ToolChains/Clang.cpp:5112
+ bool EnableSplitLTOUnit = Args.hasFlag(
+ options::OPT_fsplit_lto_unit, options::OPT_fno_split_lto_unit, false);
+ if (EnableSplitLTOUnit || WholeProgramVTables || Sanitize.needsLTO()) {
----------------
tejohnson wrote:
> pcc wrote:
> > Should this default to `WholeProgramVTables || Sanitize.needsLTO()` and
> > emit an error if the user passes the (for now) unsupported combinations
> > `-fno-split-lto-unit -fwhole-program-vtables` or `-fno-split-lto-unit
> > -fsanitize=cfi`?
> I think the code below needs to stay as is to allow -fsplit-lto-unit to also
> enable the splitting even when the other options aren't on (not sure when
> that would be used outside of testing, but I'm assuming we want a way to
> force that on).
>
> But yes I think it makes sense to emit an error on those combinations (when
> my follow on patches go in then we would remove the error with
> -fno-split-lto-unit -fwhole-program-vtables).
`-fsplit-lto-unit` is required when linking translation units compiled with
`-fsanitize=cfi` with translation units compiled without (the latter would need
the flag).
May I suggest simplifying this code as follows:
```
bool RequiresSplitLTOUnit = WholeProgramVTables || Sanitize.needsLTO();
bool SplitLTOUnit =
Args.hasFlag(options::OPT_fwhole_program_vtables,
options::OPT_fno_whole_program_vtables, RequiresSplitLTOUnit);
if (RequiresSplitLTOUnit && !SplitLTOUnit)
error;
if (SplitLTOUnit)
CmdArgs.push_back("-fsplit-lto-unit");
```
Repository:
rC Clang
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D53891/new/
https://reviews.llvm.org/D53891
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