[PATCH] D34133: Cold attribute on function decls are lost. Fix the problem

[David Li via Phabricator via cfe-commits]

davidxl created this revision.
Herald added a subscriber: sanjoy.

LLVM static branch prediction depends on cold attribute to annotate branch 
probability. This is  currently not possible for cold function decls as the 
information is dropped by FE.

This patch attaches the attributes to the callsite as noReturn. Another way is 
to pass the attribute to the function decl.

Also need suggestions on how to add a clang test case.


https://reviews.llvm.org/D34133

Files:
  lib/CodeGen/CGCall.cpp


Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp
+++ lib/CodeGen/CGCall.cpp
@@ -1795,6 +1795,8 @@
       FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
     if (TargetDecl->hasAttr<NoReturnAttr>())
       FuncAttrs.addAttribute(llvm::Attribute::NoReturn);
+    if (TargetDecl->hasAttr<ColdAttr>())
+      FuncAttrs.addAttribute(llvm::Attribute::Cold);
     if (TargetDecl->hasAttr<NoDuplicateAttr>())
       FuncAttrs.addAttribute(llvm::Attribute::NoDuplicate);
     if (TargetDecl->hasAttr<ConvergentAttr>())



Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp
+++ lib/CodeGen/CGCall.cpp
@@ -1795,6 +1795,8 @@
       FuncAttrs.addAttribute(llvm::Attribute::NoUnwind);
     if (TargetDecl->hasAttr<NoReturnAttr>())
       FuncAttrs.addAttribute(llvm::Attribute::NoReturn);
+    if (TargetDecl->hasAttr<ColdAttr>())
+      FuncAttrs.addAttribute(llvm::Attribute::Cold);
     if (TargetDecl->hasAttr<NoDuplicateAttr>())
       FuncAttrs.addAttribute(llvm::Attribute::NoDuplicate);
     if (TargetDecl->hasAttr<ConvergentAttr>())

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