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Avoid some unnecessary signed casts #70884

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Jun 27, 2022
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Avoid some unnecessary signed casts #70884

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9 changes: 7 additions & 2 deletions src/coreclr/jit/flowgraph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1277,11 +1277,16 @@ bool Compiler::fgCastNeeded(GenTree* tree, var_types toType)
return false;
}
//
// If the sign-ness of the two types are different then a cast is necessary
// If the sign-ness of the two types are different then a cast is necessary, except for
// an unsigned -> signed cast where we already know the sign bit is zero.
//
if (varTypeIsUnsigned(toType) != varTypeIsUnsigned(fromType))
{
return true;
bool isZeroExtension = varTypeIsUnsigned(fromType) && (genTypeSize(fromType) < genTypeSize(toType));
if (!isZeroExtension)
{
return true;
}
}
//
// If the from type is the same size or smaller then an additional cast is not necessary
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