Support for function summary index bitcode sections and files.

Summary:
The bitcode format is described in this document:
  https://drive.google.com/file/d/0B036uwnWM6RWdnBLakxmeDdOeXc/view
For more info on ThinLTO see:
  https://sites.google.com/site/llvmthinlto

The first customer is ThinLTO, however the data structures are designed
and named more generally based on prior feedback. There are a few
comments regarding how certain interfaces are used by ThinLTO, and the
options added here to gold currently have ThinLTO-specific names as the
behavior they provoke is currently ThinLTO-specific.

This patch includes support for generating per-module function indexes,
the combined index file via the gold plugin, and several tests
(more are included with the associated clang patch D11908).

Reviewers: dexonsmith, davidxl, joker.eph

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13107

llvm-svn: 249270

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/tools/llvm-as/llvm-as.cpp b/llvm/tools/llvm-as/llvm-as.cpp
index 4455d24fb60..d4e4d8d7107 100644
--- a/llvm/tools/llvm-as/llvm-as.cpp
+++ b/llvm/tools/llvm-as/llvm-as.cpp
@@ -45,6 +45,10 @@ static cl::opt<bool>
 DisableOutput("disable-output", cl::desc("Disable output"), cl::init(false));
 
 static cl::opt<bool>
+EmitFunctionSummary("function-summary", cl::desc("Emit function summary index"),
+                    cl::init(false));
+
+static cl::opt<bool>
 DumpAsm("d", cl::desc("Print assembly as parsed"), cl::Hidden);
 
 static cl::opt<bool>
@@ -77,7 +81,8 @@ static void WriteOutputFile(const Module *M) {
   }
 
   if (Force || !CheckBitcodeOutputToConsole(Out->os(), true))
-    WriteBitcodeToFile(M, Out->os(), PreserveBitcodeUseListOrder);
+    WriteBitcodeToFile(M, Out->os(), PreserveBitcodeUseListOrder,
+                       EmitFunctionSummary);
 
   // Declare success.
   Out->keep();