[CFI] Require -flto instead of implying it.

Summary:
This is unfortunate, but would let us land http://reviews.llvm.org/D10467,
that makes ToolChains responsible for computing the set of sanitizers
they support.

Unfortunately, Darwin ToolChains doesn't know about actual OS they
target until ToolChain::TranslateArgs() is called. In particular, it
means we won't be able to construct SanitizerArgs for these ToolChains
before that.

This change removes SanitizerArgs::needsLTO() method, so that now
ToolChain::IsUsingLTO(), which is called very early, doesn't need
SanitizerArgs to implement this method.

Docs and test cases are updated accordingly. See
https://llvm.org/bugs/show_bug.cgi?id=23539, which describes why we
start all these.

Test Plan: regression test suite

Reviewers: pcc

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D10560

llvm-svn: 240170

1 files changed, 6 insertions, 4 deletions

diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 4d27a393182..35041b56971 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -188,10 +188,6 @@ bool SanitizerArgs::needsUnwindTables() const {
   return Sanitizers.Mask & NeedsUnwindTables;
 }
 
-bool SanitizerArgs::needsLTO() const {
-  return Sanitizers.Mask & NeedsLTO;
-}
-
 void SanitizerArgs::clear() {
   Sanitizers.clear();
   RecoverableSanitizers.clear();
@@ -301,6 +297,12 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
     Kinds &= ~Vptr;
   }
 
+  // Check that LTO is enabled if we need it.
+  if ((Kinds & NeedsLTO) && !D.IsUsingLTO(Args)) {
+    D.Diag(diag::err_drv_argument_only_allowed_with)
+        << lastArgumentForMask(D, Args, Kinds & NeedsLTO) << "-flto";
+  }
+
   // Warn about incompatible groups of sanitizers.
   std::pair<SanitizerMask, SanitizerMask> IncompatibleGroups[] = {
       std::make_pair(Address, Thread), std::make_pair(Address, Memory),