[SimplifyCFG] Fix prof branch_weights MD while removing unreachable switch cases

SimplifyCFG has a bug that results in inconsistent prof branch_weights metadata
if unreachable switch cases are removed. This patch fixes this bug by making use
of the newly introduced SwitchInstProfUpdateWrapper class (see patch D62122).
A new test is created.

Differential Revision: https://reviews.llvm.org/D62186

llvm-svn: 363527

1 files changed, 5 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index ec574ea..a8d2437 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -4218,14 +4218,15 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) {
         }
       }
     } else if (auto *SI = dyn_cast<SwitchInst>(TI)) {
-      for (auto i = SI->case_begin(), e = SI->case_end(); i != e;) {
+      SwitchInstProfUpdateWrapper SU(*SI);
+      for (auto i = SU->case_begin(), e = SU->case_end(); i != e;) {
         if (i->getCaseSuccessor() != BB) {
           ++i;
           continue;
         }
-        BB->removePredecessor(SI->getParent());
-        i = SI->removeCase(i);
-        e = SI->case_end();
+        BB->removePredecessor(SU->getParent());
+        i = SU.removeCase(i);
+        e = SU->case_end();
         Changed = true;
       }
     } else if (auto *II = dyn_cast<InvokeInst>(TI)) {