[llvm] ebc4c4e - [unroll] Add clarifying comment

[Philip Reames via llvm-commits]

Author: Philip Reames
Date: 2021-08-02T10:44:56-07:00
New Revision: ebc4c4e3b060ebd92a45a590818515c4cecb279f

URL: https://github.com/llvm/llvm-project/commit/ebc4c4e3b060ebd92a45a590818515c4cecb279f
DIFF: https://github.com/llvm/llvm-project/commit/ebc4c4e3b060ebd92a45a590818515c4cecb279f.diff

LOG: [unroll] Add clarifying comment

The option to not preserve LCSSA is in fact not tested at all in upstream.  I was tempted to just remove the code entirely, but realized I didn't need to for my actual goal.

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 6749d3db743c3..cb538fd7e9ea7 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -436,6 +436,7 @@ static bool canSafelyUnrollMultiExitLoop(Loop *L, BasicBlock *LatchExit,
   // loop. Check for these below.
 
   // We rely on LCSSA form being preserved when the exit blocks are transformed.
+  // (Note that only an off-by-default mode of the old PM disables PreserveLCCA.)
   if (!PreserveLCSSA)
     return false;