Tolerate pathological growth of optCSEHash #40056
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briansull
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Jul 29, 2020
| @@ -6364,6 +6364,11 @@ class Compiler | |||
| }; | |||
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| static const size_t s_optCSEhashSize; | |||
| static const size_t s_optCSEhashGrowthFactor; | |||
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This could be renamed to indicate that it is the initial hash table size
s_optCSEhashSize => s_optCSEhashSizeInitial
src/coreclr/src/jit/compiler.h
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| @@ -6364,6 +6364,11 @@ class Compiler | |||
| }; | |||
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| static const size_t s_optCSEhashSize; | |||
| static const size_t s_optCSEhashGrowthFactor; | |||
| static const size_t s_optCSEhashBucketSize; | |||
| size_t optCSEhashSize; // Size of hashtable | |||
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// The current size of the hashtable
Jacksondr5
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Aug 10, 2020
The optCSEhash can grow an unbounded amount if the function has numerous trees which are put into the optCSEhash as possible CSE candidates, but fewer than MAX_CSE_CNT are found, then the compiler will spend excessive amounts of time looking up entries in the optCSEhash. This fix addresses the issue by making the optCSEhash able to grow its count of buckets.
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The
optCSEhashcan grow an unbounded amount if the function has numerous trees which are put into theoptCSEhashas possible CSE candidates, but fewer thanMAX_CSE_CNTare found, then the compiler will spend excessive amounts of time looking up entries in theoptCSEhash.This fix addresses the issue by making the
optCSEhashable to grow its count of buckets.This fixes #32733, but I'm not certain its the right approach. Potentially avoiding the pathological growth of the hash table would be a better approach.