Reintroduce the InlineHint function attribute.

This time it's for real! I am going to hook this up in the frontends as well.

The inliner has some experimental heuristics for dealing with the inline hint.
When given a -respect-inlinehint option, functions marked with the inline
keyword are given a threshold just above the default for -O3.

We need some experiments to determine if that is the right thing to do.

llvm-svn: 95466

3 files changed, 9 insertions, 5 deletions

diff --git a/llvm/include/llvm-c/Core.h b/llvm/include/llvm-c/Core.h
index 674dde509d5..98358fe3807 100644
--- a/llvm/include/llvm-c/Core.h
+++ b/llvm/include/llvm-c/Core.h
@@ -118,7 +118,8 @@ typedef enum {
     LLVMNoCaptureAttribute  = 1<<21,
     LLVMNoRedZoneAttribute  = 1<<22,
     LLVMNoImplicitFloatAttribute = 1<<23,
-    LLVMNakedAttribute      = 1<<24
+    LLVMNakedAttribute      = 1<<24,
+    LLVMInlineHintAttribute = 1<<25
 } LLVMAttribute;
 
 typedef enum {
diff --git a/llvm/include/llvm/Attributes.h b/llvm/include/llvm/Attributes.h
index 7fa5d4ae6bd..068f81fc7de 100644
--- a/llvm/include/llvm/Attributes.h
+++ b/llvm/include/llvm/Attributes.h
@@ -58,6 +58,8 @@ const Attributes NoRedZone = 1<<22; /// disable redzone
 const Attributes NoImplicitFloat = 1<<23; /// disable implicit floating point
                                           /// instructions.
 const Attributes Naked           = 1<<24; ///< Naked function
+const Attributes InlineHint      = 1<<25; ///< source said inlining was
+                                          ///desirable
 
 /// @brief Attributes that only apply to function parameters.
 const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
@@ -66,7 +68,7 @@ const Attributes ParameterOnly = ByVal | Nest | StructRet | NoCapture;
 /// be used on return values or function parameters.
 const Attributes FunctionOnly = NoReturn | NoUnwind | ReadNone | ReadOnly |
   NoInline | AlwaysInline | OptimizeForSize | StackProtect | StackProtectReq |
-  NoRedZone | NoImplicitFloat | Naked;
+  NoRedZone | NoImplicitFloat | Naked | InlineHint;
 
 /// @brief Parameter attributes that do not apply to vararg call arguments.
 const Attributes VarArgsIncompatible = StructRet;
diff --git a/llvm/include/llvm/Transforms/IPO/InlinerPass.h b/llvm/include/llvm/Transforms/IPO/InlinerPass.h
index dc5e644c7fe..30ece0eb422 100644
--- a/llvm/include/llvm/Transforms/IPO/InlinerPass.h
+++ b/llvm/include/llvm/Transforms/IPO/InlinerPass.h
@@ -52,10 +52,11 @@ struct Inliner : public CallGraphSCCPass {
   unsigned getInlineThreshold() const { return InlineThreshold; }
 
   /// Calculate the inline threshold for given Caller. This threshold is lower
-  /// if Caller is marked with OptimizeForSize and -inline-threshold is not
-  /// given on the comand line.
+  /// if the caller is marked with OptimizeForSize and -inline-threshold is not
+  /// given on the comand line. It is higher if the callee is marked with the
+  /// inlinehint attribute.
   ///
-  unsigned getInlineThreshold(Function* Caller) const;
+  unsigned getInlineThreshold(CallSite CS) const;
 
   /// getInlineCost - This method must be implemented by the subclass to
   /// determine the cost of inlining the specified call site.  If the cost