[PATCH] D30689: [ConstantFolding] Small fix to prevent constant folding having to repeatedly scan operands.

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.

We are seeing a case where after the unroll threshold was increased in
295538, a loop is fully unrolled into very large constant expression
chains. These are recursively scanned, leading to timeouts and hence
failures. This prevents having to rescan already scanned operands.


https://reviews.llvm.org/D30689

Files:
  lib/Analysis/ConstantFolding.cpp


Index: lib/Analysis/ConstantFolding.cpp
===================================================================
--- lib/Analysis/ConstantFolding.cpp
+++ lib/Analysis/ConstantFolding.cpp
@@ -1058,8 +1058,8 @@
       if (It == FoldedOps.end()) {
         if (auto *FoldedC =
                 ConstantFoldConstantImpl(NewC, DL, TLI, FoldedOps)) {
-          NewC = FoldedC;
           FoldedOps.insert({NewC, FoldedC});
+          NewC = FoldedC;
         } else {
           FoldedOps.insert({NewC, NewC});
         }


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