Split IndirectBr critical edges before PGO gen/use passes.

Summary:
The PGO gen/use passes currently fail with an assert failure if there's a
critical edge whose source is an IndirectBr instruction and that edge
needs to be instrumented.

To avoid this in certain cases, split IndirectBr critical edges in the PGO
gen/use passes. This works for blocks with single indirectbr predecessors,
but not for those with multiple indirectbr predecessors (splitting an
IndirectBr critical edge isn't always possible.)

Reviewers: davidxl, xur

Reviewed By: davidxl

Subscribers: efriedma, llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D40699

llvm-svn: 320511

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
index 7431edbb262..cb4b3a9c254 100644
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -716,6 +716,9 @@ BasicBlock *FuncPGOInstrumentation<Edge, BBInfo>::getInstrBB(Edge *E) {
 static void instrumentOneFunc(
     Function &F, Module *M, BranchProbabilityInfo *BPI, BlockFrequencyInfo *BFI,
     std::unordered_multimap<Comdat *, GlobalValue *> &ComdatMembers) {
+  // Split indirectbr critical edges here before computing the MST rather than
+  // later in getInstrBB() to avoid invalidating it.
+  SplitIndirectBrCriticalEdges(F, BPI, BFI);
   FuncPGOInstrumentation<PGOEdge, BBInfo> FuncInfo(F, ComdatMembers, true, BPI,
                                                    BFI);
   unsigned NumCounters = FuncInfo.getNumCounters();
@@ -1463,6 +1466,9 @@ static bool annotateAllFunctions(
       continue;
     auto *BPI = LookupBPI(F);
     auto *BFI = LookupBFI(F);
+    // Split indirectbr critical edges here before computing the MST rather than
+    // later in getInstrBB() to avoid invalidating it.
+    SplitIndirectBrCriticalEdges(F, BPI, BFI);
     PGOUseFunc Func(F, &M, ComdatMembers, BPI, BFI);
     if (!Func.readCounters(PGOReader.get()))
       continue;