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Eliminate intermediate casts to double on ARM64 #53748

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Merged
merged 2 commits into from
Jun 7, 2021
Merged

Eliminate intermediate casts to double on ARM64 #53748

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6464b53
Eliminate intermediate casts to double on ARM64
SingleAccretion Jun 4, 2021
c8c575f
Fix a typo
SingleAccretion Jun 6, 2021
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19 changes: 14 additions & 5 deletions src/coreclr/jit/morph.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -258,17 +258,26 @@ GenTree* Compiler::fgMorphCast(GenTree* tree)
}
#endif //! TARGET_64BIT

#ifdef TARGET_ARMARCH
// AArch, unlike x86/amd64, has instructions that can cast directly from
// all integers (except for longs on AArch32 of course) to floats.
// Because there is no IL instruction conv.r4.un, uint/ulong -> float
// casts are always imported as CAST(float <- CAST(double <- uint/ulong)).
// We can eliminate the redundant intermediate cast as an optimization.
else if ((dstType == TYP_FLOAT) && (srcType == TYP_DOUBLE) && oper->OperIs(GT_CAST)
#ifdef TARGET_ARM
else if ((dstType == TYP_FLOAT) && (srcType == TYP_DOUBLE) && (oper->gtOper == GT_CAST) &&
!varTypeIsLong(oper->AsCast()->CastOp()))
&& !varTypeIsLong(oper->AsCast()->CastOp())
#endif
)
{
// optimization: conv.r4(conv.r8(?)) -> conv.r4(d)
// except when the ultimate source is a long because there is no long-to-float helper, so it must be 2 step.
// This happens semi-frequently because there is no IL 'conv.r4.un'
oper->gtType = TYP_FLOAT;
oper->CastToType() = TYP_FLOAT;

return fgMorphTree(oper);
}
#endif // TARGET_ARMARCH

#ifdef TARGET_ARM
// converts long/ulong --> float/double casts into helper calls.
else if (varTypeIsFloating(dstType) && varTypeIsLong(srcType))
{
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