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JIT: Switch GS cookie check to use r9 to account for Swift #120745

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Merged
jakobbotsch merged 3 commits into from
Oct 23, 2025
Merged

JIT: Switch GS cookie check to use r9 to account for Swift #120745

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JIT: Switch GS cookie check to use r9 to account for Swift
jakobbotsch Oct 15, 2025
c03e8f5
Merge branch 'main' of github.com:dotnet/runtime into fix-swift-reg
jakobbotsch Oct 23, 2025
bdb3acd
Fix comment
jakobbotsch Oct 23, 2025
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4 changes: 2 additions & 2 deletions src/coreclr/jit/codegencommon.cpp
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Expand Up @@ -2526,8 +2526,8 @@ regMaskTP CodeGenInterface::genGetGSCookieTempRegs(bool tailCall)
// leaves rax, r10, r11. rax and r11 are used for indirection cells, so we pick r10.
return RBM_R10;
}
// Otherwise on x64 (win-x64 and SysV) r8 is never used for return values
return RBM_R8;
// Otherwise on x64 (win-x64, SysV and Swift) r9 is never used for return values
return RBM_R9;
#elif TARGET_X86
assert(!tailCall);
// On x86 it's more difficult: we have only eax, ecx and edx available as volatile
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2 changes: 1 addition & 1 deletion src/coreclr/jit/morph.cpp
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Expand Up @@ -1773,7 +1773,7 @@ void CallArgs::AddFinalArgsAndDetermineABIInfo(Compiler* comp, GenTreeCall* call
InsertAfterThisOrFirst(comp, NewCallArg::Primitive(arg).WellKnown(WellKnownArg::PInvokeCookie));
// put destination into R10/EAX
arg = comp->gtClone(call->gtCallAddr, true);
// On x64 the pinvoke target is passed in r11 which is the same
// On x64 the pinvoke target is passed in r10 which is the same
// register as the gs cookie check may use. That would be a problem if
// this was a tailcall, but we do not tailcall functions with
// non-standard added args except indirection cells currently.
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