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[JIT] X64 - Centralize peephole optimization for removing redundant
mov
instructions #85780[JIT] X64 - Centralize peephole optimization for removing redundant
mov
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Why does the
W-bit
matter here?There was a problem hiding this comment.
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W-bit on the encoding is what makes
movsx
andmovsxd
sign-extend to 8 bytes. We always default to using the W-bit. Technically, we could have amovsx
ormovsxd
instruction not set the W-bit which would not sign-extend to 8 bytes (that would be a problem and make this optimization not safe), but we never actually emit those instructions that way.There was a problem hiding this comment.
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This function cares about instructions and sizes, but not encoding, though.
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The comment
W-bit is set
itself is just meant to inform the reason why this optimization is safe to do. It was already there before.