[llvm-commits] [llvm] r113021 - /llvm/trunk/lib/Analysis/ScalarEvolutionNormalization.cpp

[Dan Gohman]

Author: djg
Date: Fri Sep  3 17:12:56 2010
New Revision: 113021

URL: http://llvm.org/viewvc/llvm-project?rev=113021&view=rev
Log:
Disable the asserts that check that normalization is perfectly
invertible. ScalarEvolution's folding routines don't always succeed
in canonicalizing equal expressions to a single canonical form, and
this can cause these asserts to fail, even though there's no actual
correctness problem. This fixes PR8066.

Modified:
    llvm/trunk/lib/Analysis/ScalarEvolutionNormalization.cpp

Modified: llvm/trunk/lib/Analysis/ScalarEvolutionNormalization.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolutionNormalization.cpp?rev=113021&r1=113020&r2=113021&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolutionNormalization.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolutionNormalization.cpp Fri Sep  3 17:12:56 2010
@@ -108,7 +108,11 @@
         Result = SE.getMinusSCEV(Result, TransformedStep);
         Loops.insert(L);
       }
-#ifdef XDEBUG
+#if 0
+      // This assert is conceptually correct, but ScalarEvolution currently
+      // sometimes fails to canonicalize two equal SCEVs to exactly the same
+      // form. It's possibly a pessimization when this happens, but it isn't a
+      // correctness problem, so disable this assert for now.
       assert(S == TransformForPostIncUse(Denormalize, Result,
                                          User, OperandValToReplace,
                                          Loops, SE, DT) &&
@@ -122,7 +126,8 @@
                                  User, OperandValToReplace, Loops, SE, DT);
         Result = SE.getMinusSCEV(Result, TransformedStep);
       }
-#ifdef XDEBUG
+#if 0
+      // See the comment on the assert above.
       assert(S == TransformForPostIncUse(Denormalize, Result,
                                          User, OperandValToReplace,
                                          Loops, SE, DT) &&