x64: Add support for the BMI2 mulx instruction
#9248
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This commit adds backend support for the `mulx` instruction in the BMI2 instruction set which supports arbitrary destination registers. This instruction also doesn't read/clobber flags so it can help pipeline instructions in niche situations.
fitzgen
approved these changes
Sep 13, 2024
| @@ -2636,6 +2651,26 @@ | |||
| (_ Unit (emit (MInst.Mul size signed src1 src2 dst_lo dst_hi)))) | |||
| (value_gprs dst_lo dst_hi))) | |||
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| ;; Special case the `mulx` pattern with the BMI2 instruction set. | |||
| (rule 1 (x64_mul (ty_32_or_64 ty) $false src1 src2) | |||
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Is there no imulx instruction for signed multiplication?
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Alas not that I can find, just an unsigned variant. I think it's geared towards bignum libraries where most of the intermediate ops are unsigned ones.
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Makes sense, thanks for checking
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This commit adds backend support for the
mulxinstruction in the BMI2 instruction set which supports arbitrary destination registers. This instruction also doesn't read/clobber flags so it can help pipeline instructions in niche situations.