[llvm] r188849 - Move registering the execution of a basic block to the beginning rather than the end.

[Bill Wendling]

Author: void
Date: Tue Aug 20 18:52:00 2013
New Revision: 188849

URL: http://llvm.org/viewvc/llvm-project?rev=188849&view=rev
Log:
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

Modified:
    llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp

Modified: llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp?rev=188849&r1=188848&r2=188849&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/GCOVProfiling.cpp Tue Aug 20 18:52:00 2013
@@ -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());