JIT: Use precise multireg arg check for old promotion #112883
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`lvaIsMultiregStruct` does not account for whether the argument was _actually_ passed in multiple regs, it just checks if the type is a type that could sometimes be passed in multiple registers. Change this to a precise check.
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This was referenced Feb 25, 2025
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EgorBo
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Feb 25, 2025
| // | ||
| bool Compiler::StructPromotionHelper::IsSysVMultiRegType(ClassLayout* layout) | ||
| { | ||
| #ifdef UNIX_AMD64_ABI |
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not the case for arm64 (sysv/win)?
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Not according to diffs... To be honest I did not spend too much time looking at why this turns out to be a good heuristic for SysV, since I hope to remove all of this in this or next release.
EgorBo
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Feb 25, 2025
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lvaIsMultiregStructdoes not account for whether the argument was actually passed in multiple regs, it just checks if the type is a type that could sometimes be passed in multiple registers. Change this to a precise check. Add a quirk for SysV where it seems the previous check provided a somewhat good heuristic.