From 40d7f5c27740f2f03e3d6731772aae073a927c7c Mon Sep 17 00:00:00 2001
From: Hal Finkel <hfinkel@anl.gov>
Date: Thu, 1 Sep 2016 09:42:39 +0000
Subject: Add a counter-function insertion pass

As discussed in https://reviews.llvm.org/D22666, our current mechanism to
support -pg profiling, where we insert calls to mcount(), or some similar
function, is fundamentally broken. We insert these calls in the frontend, which
means they get duplicated when inlining, and so the accumulated execution
counts for the inlined-into functions are wrong.

Because we don't want the presence of these functions to affect optimizaton,
they should be inserted in the backend. Here's a pass which would do just that.
The knowledge of the name of the counting function lives in the frontend, so
we're passing it here as a function attribute. Clang will be updated to use
this mechanism.

Differential Revision: https://reviews.llvm.org/D22825

llvm-svn: 280347
---
 llvm/lib/CodeGen/CodeGen.cpp | 1 +
 1 file changed, 1 insertion(+)

(limited to 'llvm/lib/CodeGen/CodeGen.cpp')

diff --git a/llvm/lib/CodeGen/CodeGen.cpp b/llvm/lib/CodeGen/CodeGen.cpp
index 5cd43df05d6..59f52ba7954 100644
--- a/llvm/lib/CodeGen/CodeGen.cpp
+++ b/llvm/lib/CodeGen/CodeGen.cpp
@@ -23,6 +23,7 @@ void llvm::initializeCodeGen(PassRegistry &Registry) {
   initializeAtomicExpandPass(Registry);
   initializeBranchFolderPassPass(Registry);
   initializeCodeGenPreparePass(Registry);
+  initializeCountingFunctionInserterPass(Registry);
   initializeDeadMachineInstructionElimPass(Registry);
   initializeDetectDeadLanesPass(Registry);
   initializeDwarfEHPreparePass(Registry);
-- 
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