From df7da79db6879032da83de83a90f981cacdb5f1a Mon Sep 17 00:00:00 2001
From: Manman Ren <manman.ren@gmail.com>
Date: Wed, 5 Feb 2014 22:53:44 +0000
Subject: [PATCH] Inliner uses a smaller inline threshold for callees with cold
 attribute.

Added command line option inlinecold-threshold to set threshold for inlining
functions with cold attribute. Listen to the cold attribute when it would
decrease the inline threshold.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200886 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/IPO/Inliner.cpp        | 11 ++++
 test/Transforms/Inline/inline-cold.ll | 88 +++++++++++++++++++++++++++
 2 files changed, 99 insertions(+)
 create mode 100644 test/Transforms/Inline/inline-cold.ll

diff --git a/lib/Transforms/IPO/Inliner.cpp b/lib/Transforms/IPO/Inliner.cpp
index dc710d14157..8647f39a900 100644
--- a/lib/Transforms/IPO/Inliner.cpp
+++ b/lib/Transforms/IPO/Inliner.cpp
@@ -50,6 +50,10 @@ static cl::opt<int>
 HintThreshold("inlinehint-threshold", cl::Hidden, cl::init(325),
               cl::desc("Threshold for inlining functions with inline hint"));
 
+static cl::opt<int>
+ColdThreshold("inlinecold-threshold", cl::Hidden, cl::init(75),
+              cl::desc("Threshold for inlining functions with cold attribute"));
+
 // Threshold to use when optsize is specified (and there is no -inline-limit).
 const int OptSizeThreshold = 75;
 
@@ -277,6 +281,13 @@ unsigned Inliner::getInlineThreshold(CallSite CS) const {
                                                Attribute::MinSize))
     thres = HintThreshold;
 
+  // Listen to the cold attribute when it would decrease the threshold.
+  bool ColdCallee = Callee && !Callee->isDeclaration() &&
+    Callee->getAttributes().hasAttribute(AttributeSet::FunctionIndex,
+                                         Attribute::Cold);
+  if (ColdCallee && ColdThreshold < thres)
+    thres = ColdThreshold;
+
   return thres;
 }
 
diff --git a/test/Transforms/Inline/inline-cold.ll b/test/Transforms/Inline/inline-cold.ll
new file mode 100644
index 00000000000..bbf4e54be40
--- /dev/null
+++ b/test/Transforms/Inline/inline-cold.ll
@@ -0,0 +1,88 @@
+; RUN: opt < %s -inline -S | FileCheck %s
+
+; Test that functions with attribute Cold are not inlined while the 
+; same function without attribute Cold will be inlined.
+
+@a = global i32 4
+
+; This function should be larger than the cold threshold (75), but smaller
+; than the regular threshold.
+; Function Attrs: nounwind readnone uwtable
+define i32 @simpleFunction(i32 %a) #0 {
+entry:
+  %a1 = load volatile i32* @a
+  %x1 = add i32 %a1,  %a1
+  %a2 = load volatile i32* @a
+  %x2 = add i32 %x1, %a2
+  %a3 = load volatile i32* @a
+  %x3 = add i32 %x2, %a3
+  %a4 = load volatile i32* @a
+  %x4 = add i32 %x3, %a4
+  %a5 = load volatile i32* @a
+  %x5 = add i32 %x4, %a5
+  %a6 = load volatile i32* @a
+  %x6 = add i32 %x5, %a6
+  %a7 = load volatile i32* @a
+  %x7 = add i32 %x6, %a6
+  %a8 = load volatile i32* @a
+  %x8 = add i32 %x7, %a8
+  %a9 = load volatile i32* @a
+  %x9 = add i32 %x8, %a9
+  %a10 = load volatile i32* @a
+  %x10 = add i32 %x9, %a10
+  %a11 = load volatile i32* @a
+  %x11 = add i32 %x10, %a11
+  %a12 = load volatile i32* @a
+  %x12 = add i32 %x11, %a12
+  %add = add i32 %x12, %a
+  ret i32 %add
+}
+
+; Function Attrs: nounwind cold readnone uwtable
+define i32 @ColdFunction(i32 %a) #1 {
+; CHECK-LABEL: @ColdFunction
+; CHECK: ret
+entry:
+  %a1 = load volatile i32* @a
+  %x1 = add i32 %a1,  %a1
+  %a2 = load volatile i32* @a
+  %x2 = add i32 %x1, %a2
+  %a3 = load volatile i32* @a
+  %x3 = add i32 %x2, %a3
+  %a4 = load volatile i32* @a
+  %x4 = add i32 %x3, %a4
+  %a5 = load volatile i32* @a
+  %x5 = add i32 %x4, %a5
+  %a6 = load volatile i32* @a
+  %x6 = add i32 %x5, %a6
+  %a7 = load volatile i32* @a
+  %x7 = add i32 %x6, %a6
+  %a8 = load volatile i32* @a
+  %x8 = add i32 %x7, %a8
+  %a9 = load volatile i32* @a
+  %x9 = add i32 %x8, %a9
+  %a10 = load volatile i32* @a
+  %x10 = add i32 %x9, %a10
+  %a11 = load volatile i32* @a
+  %x11 = add i32 %x10, %a11
+  %a12 = load volatile i32* @a
+  %x12 = add i32 %x11, %a12
+  %add = add i32 %x12, %a
+  ret i32 %add
+}
+
+; Function Attrs: nounwind readnone uwtable
+define i32 @bar(i32 %a) #0 {
+; CHECK-LABEL: @bar
+; CHECK: call i32 @ColdFunction(i32 5)
+; CHECK-NOT: call i32 @simpleFunction(i32 6)
+; CHECK: ret
+entry:
+  %0 = tail call i32 @ColdFunction(i32 5)
+  %1 = tail call i32 @simpleFunction(i32 6)
+  %add = add i32 %0, %1
+  ret i32 %add
+}
+
+attributes #0 = { nounwind readnone uwtable }
+attributes #1 = { nounwind cold readnone uwtable }