[PATCH] D65596: [SimplifyCFG] Cleanup redundant conditions [NFC].

[Alina Sbirlea via Phabricator via llvm-commits]

asbirlea created this revision.
asbirlea added a reviewer: sanjoy.google.
Herald added a subscriber: jlebar.
Herald added a project: LLVM.

Since the for loop iterates over BB's predecessors, the branch conditions found must have BB as one of the successors.
For an unconditional branch the successor must be BB, added `assert`.
For a conditional branch, one of the two successors must be BB, simplify `else if` to `else` and `assert`.
Sink common instructions outside the if/else block.


Repository:
  rL LLVM

https://reviews.llvm.org/D65596

Files:
  lib/Transforms/Utils/SimplifyCFG.cpp


Index: lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyCFG.cpp
+++ lib/Transforms/Utils/SimplifyCFG.cpp
@@ -4178,24 +4178,22 @@
     IRBuilder<> Builder(TI);
     if (auto *BI = dyn_cast<BranchInst>(TI)) {
       if (BI->isUnconditional()) {
-        if (BI->getSuccessor(0) == BB) {
-          new UnreachableInst(TI->getContext(), TI);
-          TI->eraseFromParent();
-          Changed = true;
-        }
+        assert(BI->getSuccessor(0) == BB && "Incorrect CFG");
+        new UnreachableInst(TI->getContext(), TI);
+        TI->eraseFromParent();
+        Changed = true;
       } else {
         Value* Cond = BI->getCondition();
         if (BI->getSuccessor(0) == BB) {
           Builder.CreateAssumption(Builder.CreateNot(Cond));
           Builder.CreateBr(BI->getSuccessor(1));
-          EraseTerminatorAndDCECond(BI);
-          Changed = true;
-        } else if (BI->getSuccessor(1) == BB) {
+        } else {
+          assert(BI->getSuccessor(1) == BB && "Incorrect CFG");
           Builder.CreateAssumption(Cond);
           Builder.CreateBr(BI->getSuccessor(0));
-          EraseTerminatorAndDCECond(BI);
-          Changed = true;
         }
+        EraseTerminatorAndDCECond(BI);
+        Changed = true;
       }
     } else if (auto *SI = dyn_cast<SwitchInst>(TI)) {
       SwitchInstProfUpdateWrapper SU(*SI);


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