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Optimize casts from constant byrefs #99130

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Optimize casts from constant byrefs #99130

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ad35f3a
Optimize casts from constant byrefs
MichalPetryka Feb 29, 2024
e52a42b
Retype BYREF constants instead of folding a new cast
MichalPetryka Mar 2, 2024
d234bef
Merge branch 'main' into byref-cast
MichalPetryka Mar 22, 2024
002f7ef
Merge branch 'main' into byref-cast
MichalPetryka Jun 14, 2024
c2fca8f
Merge branch 'main' into byref-cast
MichalPetryka Jan 6, 2025
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8 changes: 8 additions & 0 deletions src/coreclr/jit/morph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -577,6 +577,14 @@ GenTree* Compiler::fgMorphExpandCast(GenTreeCast* tree)
// we fix this by copying the GC pointer to a non-gc pointer temp.
noway_assert(!varTypeIsGC(dstType) && "How can we have a cast to a GCRef here?");

// we can just retype byref constants
if (oper->IsCnsIntOrI() && oper->TypeIs(TYP_BYREF) && varTypeIsI(dstType))
{
assert(srcType == TYP_BYREF);
oper->gtType = dstType;
return fgMorphTree(oper);
}

// We generate a store to an int and then do the cast from an int. With this we avoid
// the gc problem and we allow casts to bytes, longs, etc...
unsigned lclNum = lvaGrabTemp(true DEBUGARG("Cast away GC"));
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