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Fix incoming arg struct splitting#71701

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BruceForstall merged 1 commit intodotnet:mainfrom
BruceForstall:Fix57606
Jul 7, 2022
Merged

Fix incoming arg struct splitting#71701
BruceForstall merged 1 commit intodotnet:mainfrom
BruceForstall:Fix57606

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@BruceForstall BruceForstall commented Jul 6, 2022

This only affects Windows/arm64 with varargs.

For incoming structs split between register and stack, handle the splitting
correctly.

Fixes #57606

@ghost ghost added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Jul 6, 2022
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Issue Details

This only affects Windows/arm64 with varargs.

For incoming structs split between register and stack, handle the splitting
correctly.

Fixes #57606

Author: BruceForstall
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area-CodeGen-coreclr
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BruceForstall commented Jul 6, 2022

Note this comment in lvaInitUserArgs:

runtime/src/coreclr/jit/lclvars.cpp

Lines 724 to 741 in cd88b84

#if defined(TARGET_ARM64)
if (compFeatureArgSplit())
{
// On arm64 Windows we will need to properly handle the case where a >8byte <=16byte
// struct is split between register r7 and virtual stack slot s[0]
// We will only do this for calls to vararg methods on Windows Arm64
//
// !!This does not affect the normal arm64 calling convention or Unix Arm64!!
if (this->info.compIsVarArgs && argType == TYP_STRUCT)
{
if (varDscInfo->canEnreg(TYP_INT, 1) && // The beginning of the struct can go in a register
!varDscInfo->canEnreg(TYP_INT, cSlots)) // The end of the struct can't fit in a register
{
cSlotsToEnregister = 1; // Force the split
}
}
}

@runfoapp runfoapp bot mentioned this pull request Jul 6, 2022
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@BruceForstall
Fix incoming arg struct splitting
5749682 
This change only affects Windows/arm64 with varargs.

For incoming structs split between register and stack, handle the splitting
correctly.

Fixes dotnet#57606
@BruceForstall BruceForstall requested a review from jakobbotsch July 7, 2022 05:02
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BruceForstall commented Jul 7, 2022

@jakobbotsch @dotnet/jit-contrib PTAL

@BruceForstall BruceForstall merged commit e633272 into dotnet:main Jul 7, 2022
@BruceForstall BruceForstall deleted the Fix57606 branch July 7, 2022 16:14
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BruceForstall commented Jul 7, 2022

No diffs

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@jakobbotsch jakobbotsch jakobbotsch approved these changes

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Assertion failed 'regArgTab[regArgNum + i].slot == 0'

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