[PGO] Fix PGO use ICE when there are unreachable BBs

For -O0 there might be unreachable BBs, which breaks the assumption that all the
BBs have an auxiliary data structure.  In this patch, we add another interface
called findBBInfo() so that a nullptr can be returned for the unreachable BBs
(and the callers can ignore those BBs).

This fixes the bug reported
https://llvm.org/bugs/show_bug.cgi?id=31209

Differential Revision: https://reviews.llvm.org/D27280

llvm-svn: 288528

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/CFGMST.h b/llvm/lib/Transforms/Instrumentation/CFGMST.h
index 3cd7351cad6..3802f9fbf7d 100644
--- a/llvm/lib/Transforms/Instrumentation/CFGMST.h
+++ b/llvm/lib/Transforms/Instrumentation/CFGMST.h
@@ -78,6 +78,14 @@ public:
     return *It->second.get();
   }
 
+  // Give BB, return the auxiliary information if it's available.
+  BBInfo *findBBInfo(const BasicBlock *BB) const {
+    auto It = BBInfos.find(BB);
+    if (It == BBInfos.end())
+      return nullptr;
+    return It->second.get();
+  }
+
   // Traverse the CFG using a stack. Find all the edges and assign the weight.
   // Edges with large weight will be put into MST first so they are less likely
   // to be instrumented.