[llvm] r226443 - [PM] Relax asserts and always try to reconstruct loop simplify form when

[Chandler Carruth]

Author: chandlerc
Date: Mon Jan 19 04:23:00 2015
New Revision: 226443

URL: http://llvm.org/viewvc/llvm-project?rev=226443&view=rev
Log:
[PM] Relax asserts and always try to reconstruct loop simplify form when
we can while splitting critical edges.

The only code which called this and didn't require simplified loops to
be preserved is polly, and the code behaves correctly there anyways.
Without this change, it becomes really hard to share this code with the
new pass manager where things like preserving loop simplify form don't
make any sense.

If anyone discovers this code behaving incorrectly, what it *should* be
testing for is whether the loops it needs to be in simplified form are
in fact in that form. It should always be trying to preserve that form
when it exists.

Modified:
    llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp

Modified: llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp?rev=226443&r1=226442&r2=226443&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/BreakCriticalEdges.cpp Mon Jan 19 04:23:00 2015
@@ -291,16 +291,17 @@ BasicBlock *llvm::SplitCriticalEdge(Term
             P->addBasicBlockToLoop(NewBB, *LI);
         }
       }
+
       // If TIBB is in a loop and DestBB is outside of that loop, we may need
       // to update LoopSimplify form and LCSSA form.
-      if (!TIL->contains(DestBB) &&
-          P->mustPreserveAnalysisID(LoopSimplifyID)) {
+      if (!TIL->contains(DestBB)) {
         assert(!TIL->contains(NewBB) &&
                "Split point for loop exit is contained in loop!");
 
         // Update LCSSA form in the newly created exit block.
-        if (PreserveLCSSA)
+        if (PreserveLCSSA) {
           createPHIsForSplitLoopExit(TIBB, NewBB, DestBB);
+        }
 
         // The only that we can break LoopSimplify form by splitting a critical
         // edge is if after the split there exists some edge from TIL to DestBB
@@ -333,13 +334,6 @@ BasicBlock *llvm::SplitCriticalEdge(Term
             createPHIsForSplitLoopExit(LoopPreds, NewExitBB, DestBB);
         }
       }
-      // LCSSA form was updated above for the case where LoopSimplify is
-      // available, which means that all predecessors of loop exit blocks
-      // are within the loop. Without LoopSimplify form, it would be
-      // necessary to insert a new phi.
-      assert((!PreserveLCSSA || P->mustPreserveAnalysisID(LoopSimplifyID)) &&
-             "SplitCriticalEdge doesn't know how to update LCCSA form "
-             "without LoopSimplify!");
     }
   }