Assertion failed '(tree->gtFlags & (GTF_SIDE_EFFECT & ~GTF_CALL)) == 0'

[BruceForstall]

This assert is hitting in (apparently) all outerloop jobs (including all stress jobs) in

JIT\\Methodical\\ELEMENT_TYPE_IU\\_il_reli_conv\\_il_reli_conv.cmd
JIT\\Methodical\\ELEMENT_TYPE_IU\\_il_relu_conv\\_il_relu_conv.cmd

\r\nAssert failure(PID 4712 [0x00001268], Thread: 548 [0x0224]): Assertion failed '(tree->gtFlags & (GTF_SIDE_EFFECT & ~GTF_CALL)) == 0' in 'Test:Main():int' (IL size 561)\r\n\r\n File: F:\workspace\_work\1\s\src\coreclr\src\jit\flowgraph.cpp Line: 22630\r\n Image: C:\h\w\AFC20959\p\CoreRun.exe\r\n\r\n\r\nReturn code: 1\r\nRaw output file: C:\h\w\AFC20959\w\9BE108B1\e\JIT\Methodical\Reports\JIT.Methodical\ELEMENT_TYPE_IU\_il_reli_conv\_il_reli_conv.output.txt\r\nRaw output:\r\nBEGIN EXECUTION\r\n "C:\h\w\AFC20959\p\corerun.exe" _il_reli_conv.dll \r\nExpected: 100\r\nActual: -1073740286\r\nEND EXECUTION - FAILED\r\nFAILED\r\nTest Harness Exitcode is : 1\r\nTo run the test:\r\n> set CORE_ROOT=C:\h\w\AFC20959\p\r\n> C:\h\w\AFC20959\w\9BE108B1\e\JIT\Methodical\ELEMENT_TYPE_IU\_il_reli_conv\_il_reli_conv.cmd\r\nExpected: True\r\nActual: False

It appears this started:

https://dev.azure.com/dnceng/public/_build/results?buildId=504908&view=ms.vss-test-web.build-test-results-tab&runId=16031852&resultId=109157&paneView=debug

due to #1751

@AndyAyersMS
cc @dotnet/jit-contrib