[Clang] Implement function attribute no_stack_protector.

Summary:
This attribute tells clang to skip this function from stack protector
when -stack-protector option is passed.
GCC option for this is:
__attribute__((__optimize__("no-stack-protector"))) and the
equivalent clang syntax would be: __attribute__((no_stack_protector))

This is used in Linux kernel to selectively disable stack protector
in certain functions.

Reviewers: aaron.ballman, rsmith, rnk, probinson

Reviewed By: aaron.ballman

Subscribers: probinson, srhines, cfe-commits

Differential Revision: https://reviews.llvm.org/D46300

llvm-svn: 331925

1 files changed, 8 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index bfdd1e65e2c..3a27d999352 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1142,12 +1142,14 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
   if (!hasUnwindExceptions(LangOpts))
     B.addAttribute(llvm::Attribute::NoUnwind);
 
-  if (LangOpts.getStackProtector() == LangOptions::SSPOn)
-    B.addAttribute(llvm::Attribute::StackProtect);
-  else if (LangOpts.getStackProtector() == LangOptions::SSPStrong)
-    B.addAttribute(llvm::Attribute::StackProtectStrong);
-  else if (LangOpts.getStackProtector() == LangOptions::SSPReq)
-    B.addAttribute(llvm::Attribute::StackProtectReq);
+  if (!D || !D->hasAttr<NoStackProtectorAttr>()) {
+    if (LangOpts.getStackProtector() == LangOptions::SSPOn)
+      B.addAttribute(llvm::Attribute::StackProtect);
+    else if (LangOpts.getStackProtector() == LangOptions::SSPStrong)
+      B.addAttribute(llvm::Attribute::StackProtectStrong);
+    else if (LangOpts.getStackProtector() == LangOptions::SSPReq)
+      B.addAttribute(llvm::Attribute::StackProtectReq);
+  }
 
   if (!D) {
     // If we don't have a declaration to control inlining, the function isn't