[MachineBlockPlacement] Make sure PreferredLoopExit is cleared everytime new loop is processed
Summary: Rotate on exit that actually exits the current loop.
Reviewers: davidxl, danielcdh, iteratee, chandlerc
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38563
llvm-svn: 314937
diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
index f135cf7..12d8a9a 100644
--- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
@@ -2233,9 +2233,19 @@
// If we selected just the header for the loop top, look for a potentially
// profitable exit block in the event that rotating the loop can eliminate
// branches by placing an exit edge at the bottom.
+ //
+ // Loops are processed innermost to uttermost, make sure we clear
+ // PreferredLoopExit before processing a new loop.
+ PreferredLoopExit = nullptr;
if (!RotateLoopWithProfile && LoopTop == L.getHeader())
PreferredLoopExit = findBestLoopExit(L, LoopBlockSet);
+ // Make sure PreferredLoopExit actually exits the current loop.
+ if (PreferredLoopExit) {
+ assert(L.isLoopExiting(PreferredLoopExit) &&
+ "not an exiting block of current loop");
+ }
+
BlockChain &LoopChain = *BlockToChain[LoopTop];
// FIXME: This is a really lame way of walking the chains in the loop: we