commit ac7b5bb79899865b2375d14bc3af2079ec2eb28d
author TDYa127 <tdy@google.com> Fri May 11 13:17:49 2012 -0700
committer Shih-wei Liao <sliao@google.com> Sat May 12 00:57:37 2012 -0700
tree a835cbd1158a04bb01ea3505a6a5e561e0f9d527
parent 6819a91aa4e9c59a555a8fd14f4be263ae5d8dbb

Add support for llvm static branch prediction.

Change-Id: I8025db404d59a7ef17e4f8b878d0ab5c8cf7dab4

src/compiler_llvm/ir_builder.cc

diff --git a/src/compiler_llvm/ir_builder.cc b/src/compiler_llvm/ir_builder.cc
index 8b2f0f7..d93b588 100644
--- a/src/compiler_llvm/ir_builder.cc
+++ b/src/compiler_llvm/ir_builder.cc
@@ -19,6 +19,8 @@
 
 #include <llvm/Module.h>
 
+#include <algorithm>
+
 namespace art {
 namespace compiler_llvm {
 
@@ -44,6 +46,22 @@
   CHECK(art_frame_type_ != NULL);
 
   runtime_support_ = NULL;
+
+
+  // Pre-generate the MDNode for static branch prediction
+  llvm::Type* int32ty = llvm::Type::getInt32Ty(context);
+  llvm::MDString* branch_weights = llvm::MDString::get(context, "branch_weights");
+  llvm::Constant* likely = llvm::ConstantInt::get(int32ty, 64);
+  llvm::Constant* unlikely = llvm::ConstantInt::get(int32ty, 4);
+  llvm::Value *opts[] = {
+    branch_weights,
+    likely,
+    unlikely
+  };
+
+  expect_cond_[kLikely] = llvm::MDNode::get(context, opts);
+  std::swap(opts[1], opts[2]);
+  expect_cond_[kUnlikely] = llvm::MDNode::get(context, opts);
 }