[CodeGen] Merge equivalent block copy/helper functions.

Clang generates copy and dispose helper functions for each block literal
on the stack. Often these functions are equivalent for different blocks.
This commit makes changes to merge equivalent copy and dispose helper
functions and reduce code size.

To enable merging equivalent copy/dispose functions, the captured object
infomation is encoded into the helper function name. This allows IRGen
to check whether an equivalent helper function has already been emitted
and reuse the function instead of generating a new helper function
whenever a block is defined. In addition, the helper functions are
marked as linkonce_odr to enable merging helper functions that have the
same name across translation units and marked as unnamed_addr to enable
the linker's deduplication pass to merge functions that have different
names but the same content.

rdar://problem/42640608

Differential Revision: https://reviews.llvm.org/D50152

llvm-svn: 339438

1 files changed, 5 insertions, 7 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 98975a8c752..030101d2f4e 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -772,9 +772,11 @@ static bool endsWithReturn(const Decl* F) {
   return false;
 }
 
-static void markAsIgnoreThreadCheckingAtRuntime(llvm::Function *Fn) {
-  Fn->addFnAttr("sanitize_thread_no_checking_at_run_time");
-  Fn->removeFnAttr(llvm::Attribute::SanitizeThread);
+void CodeGenFunction::markAsIgnoreThreadCheckingAtRuntime(llvm::Function *Fn) {
+  if (SanOpts.has(SanitizerKind::Thread)) {
+    Fn->addFnAttr("sanitize_thread_no_checking_at_run_time");
+    Fn->removeFnAttr(llvm::Attribute::SanitizeThread);
+  }
 }
 
 static bool matchesStlAllocatorFn(const Decl *D, const ASTContext &Ctx) {
@@ -887,10 +889,6 @@ void CodeGenFunction::StartFunction(GlobalDecl GD,
           (OMD->getSelector().isUnarySelector() && II->isStr(".cxx_destruct"))) {
         markAsIgnoreThreadCheckingAtRuntime(Fn);
       }
-    } else if (const auto *FD = dyn_cast_or_null<FunctionDecl>(D)) {
-      IdentifierInfo *II = FD->getIdentifier();
-      if (II && II->isStr("__destroy_helper_block_"))
-        markAsIgnoreThreadCheckingAtRuntime(Fn);
     }
   }