8309636: C2: Optimize ModD to ModL when operands are integral numbers

[krk]

drem calls fmod (slow) even when both operands are integer-valued doubles, which is common for values derived from int/long conversions.

When the divisor is a constant integer-valued double, replace drem with ModL. If the dividend is provably integral, the replacement is unconditional. Otherwise, a speculative guard checks integrality at runtime and falls back to fmod.

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• JDK-8309636: C2: Optimize ModD to ModL when operands are integral numbers (Enhancement - P4)

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