commit 2f3862eb9f21e8a0d48505637fefe6e5e295c18c
Author: Roman Lebedev <lebedev.ri@gmail.com>
Date:   Sun Jul 19 16:37:03 2020 +0300

    Reland "[InstCombine] Lower infinite combine loop detection thresholds"
    
    This reverts commit 4500db8c59621a31c622862a2946457fdee481ce,
    which was reverted because lower thresholds exposed a new issue (PR46680).
    
    Now that it was resolved by d12ec0f752e7f2c7f7252539da2d124264ec33f7,
    we can reinstate lower limits and wait for a new bugreport before
    reverting this again...

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index b3254c10a0b..8eac8637cb9 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -123,8 +123,13 @@ STATISTIC(NumReassoc  , "Number of reassociations");
 DEBUG_COUNTER(VisitCounter, "instcombine-visit",
               "Controls which instructions are visited");
 
+// FIXME: these limits eventually should be as low as 2.
 static constexpr unsigned InstCombineDefaultMaxIterations = 1000;
+#ifndef NDEBUG
+static constexpr unsigned InstCombineDefaultInfiniteLoopThreshold = 100;
+#else
 static constexpr unsigned InstCombineDefaultInfiniteLoopThreshold = 1000;
+#endif
 
 static cl::opt<bool>
 EnableCodeSinking("instcombine-code-sinking", cl::desc("Enable code sinking"),