[SimpleLoopUnswitch] Form dedicated exits after trivial unswitches.
Summary:
Form dedicated exits after trivial unswitches.
Fixes PR38737, PR38283.
Reviewers: chandlerc, fedor.sergeev
Subscribers: sanjoy, jlebar, uabelho, llvm-commits
Differential Revision: https://reviews.llvm.org/D51375
llvm-svn: 340871
diff --git a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
index 5834b61..8b67c47 100644
--- a/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
+++ b/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp
@@ -302,10 +302,11 @@
formLCSSA(*OldContainingL, DT, &LI, nullptr);
// We shouldn't need to form dedicated exits because the exit introduced
- // here is the (just split by unswitching) preheader. As such, it is
- // necessarily dedicated.
- assert(OldContainingL->hasDedicatedExits() &&
- "Unexpected predecessor of hoisted loop preheader!");
+ // here is the (just split by unswitching) preheader. However, after trivial
+ // unswitching it is possible to get new non-dedicated exits out of parent
+ // loop so let's conservatively form dedicated exit blocks and figure out
+ // if we can optimize later.
+ formDedicatedExitBlocks(OldContainingL, &DT, &LI, /*PreserveLCSSA*/ true);
}
}
@@ -482,6 +483,7 @@
if (FullUnswitch)
hoistLoopToNewParent(L, *NewPH, DT, LI);
+ LLVM_DEBUG(dbgs() << " done: unswitching trivial branch...\n");
++NumTrivial;
++NumBranches;
return true;
@@ -539,7 +541,7 @@
else if (ExitCaseIndices.empty())
return false;
- LLVM_DEBUG(dbgs() << " unswitching trivial cases...\n");
+ LLVM_DEBUG(dbgs() << " unswitching trivial switch...\n");
// We may need to invalidate SCEVs for the outermost loop reached by any of
// the exits.
@@ -739,6 +741,7 @@
++NumTrivial;
++NumSwitches;
+ LLVM_DEBUG(dbgs() << " done: unswitching trivial switch...\n");
return true;
}