[release/9.0] JIT: don't create vector constants from relocatable constants#107500
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jeffschwMSFT merged 3 commits intorelease/9.0from Sep 11, 2024
Merged
[release/9.0] JIT: don't create vector constants from relocatable constants#107500jeffschwMSFT merged 3 commits intorelease/9.0from
jeffschwMSFT merged 3 commits intorelease/9.0from
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We can't represent relocations in data currently. Fixes #107396.
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approved. we can merge when ready
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Backport of #107491 to release/9.0
/cc @AndyAyersMS
Customer Impact
#107396
The JIT can coalesce adjacent scalar stores into a single vector store. If the values being stored are constant, then the value being stored is usually not expressible as a literal (in-code) constant and so the JIT will allocate a data segment for the constant.
However, certain constants (like function addresses) may be relocatable and need adjustment at link or load time, and there is currently no mechanism to report relocations for JIT-created data segments.
As a result, programs relying on these constants may crash, compute the wrong values, try and jump to somewhat arbitrary addresses, etc.
This fix blocks the jit from coalescing stores for relocatable constants.
Regression
Store coalescing is new in .NET 9: #92852
Testing
Verified on test case from the issue.
Risk
Low. The fix stops the jit from doing an optional optimization, reverting for those cases to .NET 8 behavior.