[LCSSA] Remove redundant check

[davide]

Summary

formLCSSA checks that the set of exit block is not empty, and then calls formLCSSAForInstructions which does the same check again.
AFAICT there's nothing changing the set of exit blocks in the meanwhile, making the second check redundant.

[mzolotukhin]

Can you verify that by inserting an assertion there?

One thing that I'm not 100% sure there is that we might be looking at different loops in formLCSSA and formLCSSAForInstructions. In the latter we might look at subloops as far as I can tell.

Michael

[davide]

In D31730#719604, @mzolotukhin wrote:

Can you verify that by inserting an assertion there?

One thing that I'm not 100% sure there is that we might be looking at different loops in formLCSSA and formLCSSAForInstructions. In the latter we might look at subloops as far as I can tell.

Michael

Nevermind, I read the code again and I realized we actually can call that on subloops.

lib/Transforms/Utils/LCSSA.cpp

while (!Worklist.empty()) {
     Instruction *I = Worklist.pop_back_val();
     BasicBlock *InstBB = I->getParent();
     Loop *L = LI.getLoopFor(InstBB);
     if (!LoopExitBlocks.count(L))   
       L->getExitBlocks(LoopExitBlocks[L]);
     assert(LoopExitBlocks.count(L));
     const SmallVectorImpl<BasicBlock *> &ExitBlocks = LoopExitBlocks[L];
 
-    if (ExitBlocks.empty())
-      continue;
-
     // Tokens cannot be used in PHI nodes, so we skip over them.
     // We can run into tokens which are live out of a loop with catchswitch
     // instructions in Windows EH if the catchswitch has one catchpad which
     // is inside the loop and another which is not.
     if (I->getType()->isTokenTy())
       continue;
 
     for (Use &U : I->uses()) {