Fix incorrect faulting instruction update in BNDCHK implicit null check - #24586
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Fix incorrect faulting instruction update in BNDCHK implicit null check#24586AbdallahAbd05 wants to merge 1 commit into
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Thanks for figuring out the problem. I think the change looks correct. May I ask you to provide more information in the commit comment indicating why the change is being made? Some of the same information that you've provided in the pull request description above would be appropriate. Also, could you add a comment here showing the relevant IL that could give rise to a |
When a BNDCHK has a foldedImplicitNULLCHK, the function setImplicitNULLCHKExceptionInfo attempts to correctly identify the faulting instruction. The condition checked for both CMP4MemReg and CMP4RegMem, but CMP4RegMem loads from an object field rather than the array, so it cannot be the faulting instruction for a null array access. This caused the stack walker to fail to find the stack map, hitting a fatal assertion in jswalk.c. The fix removes CMP4RegMem from the condition, keeping only CMP4MemReg which correctly identifies a cmp that loads array length from the array.
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When a
BNDCHKhas afoldedImplicitNULLCHK, the functionsetImplicitNULLCHKExceptionInfoattempts to correctly identify the faulting instruction. The condition checked for bothCMP4MemRegandCMP4RegMem, butCMP4RegMemloads from an object field (e.g. idx from 'this') rather than the array, so it cannot be the faulting instruction for a null array access. This caused the stack walker to fail to find the stack map, hitting a fatal assertion in jswalk.c.The fix removes
CMP4RegMemfrom the condition, keeping onlyCMP4MemRegwhich correctly identifies a cmp that loads array length from the array.Fixes #24569