From 707f601fa5a82a1d9e114469311672b012cc76fc Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Tue, 20 Aug 2013 23:52:00 +0000
Subject: [PATCH] Move registering the execution of a basic block to the
 beginning rather than the end.

There are situations which can affect the correctness (or at least expectation)
of the gcov output. For instance, if a call to __gcov_flush() occurs within a
block before the execution count is registered and then the program aborts in
some way, then that block will not be marked as executed. This is not normally
what the user expects.

If we move the code that's registering when a block is executed to the
beginning, we can catch these types of situations.

PR16893

llvm-svn: 188849
---
 llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp b/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
index 4c2681f..61c53b4 100644
--- a/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
+++ b/llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
@@ -519,15 +519,15 @@ bool GCOVProfiler::emitProfileArcs() {
         TerminatorInst *TI = BB->getTerminator();
         int Successors = isa<ReturnInst>(TI) ? 1 : TI->getNumSuccessors();
         if (Successors) {
-          IRBuilder<> Builder(TI);
-          
           if (Successors == 1) {
+            IRBuilder<> Builder(BB->getFirstInsertionPt());
             Value *Counter = Builder.CreateConstInBoundsGEP2_64(Counters, 0,
                                                                 Edge);
             Value *Count = Builder.CreateLoad(Counter);
             Count = Builder.CreateAdd(Count, Builder.getInt64(1));
             Builder.CreateStore(Count, Counter);
           } else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+            IRBuilder<> Builder(BI);
             Value *Sel = Builder.CreateSelect(BI->getCondition(),
                                               Builder.getInt64(Edge),
                                               Builder.getInt64(Edge + 1));
@@ -543,6 +543,7 @@ bool GCOVProfiler::emitProfileArcs() {
             for (int i = 0; i != Successors; ++i)
               ComplexEdgeSuccs.insert(TI->getSuccessor(i));
           }
+
           Edge += Successors;
         }
       }
@@ -554,14 +555,13 @@ bool GCOVProfiler::emitProfileArcs() {
         GlobalVariable *EdgeState = getEdgeStateValue();
         
         for (int i = 0, e = ComplexEdgePreds.size(); i != e; ++i) {
-          IRBuilder<> Builder(ComplexEdgePreds[i+1]->getTerminator());
+          IRBuilder<> Builder(ComplexEdgePreds[i + 1]->getFirstInsertionPt());
           Builder.CreateStore(Builder.getInt32(i), EdgeState);
         }
+
         for (int i = 0, e = ComplexEdgeSuccs.size(); i != e; ++i) {
-          // call runtime to perform increment
-          BasicBlock::iterator InsertPt =
-            ComplexEdgeSuccs[i+1]->getFirstInsertionPt();
-          IRBuilder<> Builder(InsertPt);
+          // Call runtime to perform increment.
+          IRBuilder<> Builder(ComplexEdgeSuccs[i+1]->getFirstInsertionPt());
           Value *CounterPtrArray =
             Builder.CreateConstInBoundsGEP2_64(EdgeTable, 0,
                                                i * ComplexEdgePreds.size());
-- 
2.7.4