IR: Change clang to set -preserve-bc-uselistorder
Change `clang` to set `-preserve-bc-uselistorder` for the driver options
`-emit-llvm` and `-save-temps`. The former is useful for reproducing
results from `clang` in `opt` or `llc`, while the latter prevents
`-save-temps` from affecting the output. This is part of PR5680.
`-preserve-bc-uselistorder=true` is currently on by default, but a
follow-up commit in LLVM will reverse it.
llvm-svn: 234920
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 1e34d7f..2d2526c 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -2678,6 +2678,15 @@
assert(JA.getType() == types::TY_PP_Asm &&
"Unexpected output type!");
}
+
+ // Preserve use-list order by default when emitting bitcode, so that
+ // loading the bitcode up in 'opt' or 'llc' and running passes gives the
+ // same result as running passes here. For LTO, we don't need to preserve
+ // the use-list order, since serialization to bitcode is part of the flow.
+ if (JA.getType() == types::TY_LLVM_BC) {
+ CmdArgs.push_back("-mllvm");
+ CmdArgs.push_back("-preserve-bc-uselistorder");
+ }
}
// We normally speed up the clang process a bit by skipping destructors at