Do some minor enhancements of the code generation in the JIT #7956
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jhogberg
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Dec 19, 2023
jhogberg
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Dec 19, 2023
jhogberg
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Dec 19, 2023
Leverage the bitfield manipulation instructions to optimize matching.
Consider this example:
bm(<<X:16, Y:16, Z:16>>) ->
{X, Y, Z}.
In OTP 26, the code for extracting the `X`, `Y`, and `Z` variables looks
like this:
# extract integer 16
ror x7, x7, 48
mov x27, 15
bfi x27, x7, 4, 16
# extract integer 16
ror x7, x7, 48
mov x28, 15
bfi x28, x7, 4, 16
# extract integer 16
ror x7, x7, 48
mov x15, 15
bfi x15, x7, 4, 16
With this commit, the code is simplified to:
# extract integer 16
mov x4, 15
orr x27, x4, x7, 44
# extract integer 16
ubfx x9, x7, 32, 16
orr x28, x4, x9, 4
# extract integer 16
ubfx x9, x7, 16, 16
orr x15, x4, x9, 4
Consider this example:
bb(<<X:8, Y:8, Z:8>>) ->
<<X:16, Y:16, Z:16>>.
In OTP 26, the code for constructing the binary from the values of
`X`, `Y`, and `Z` looks like this:
# accumulate value for integer segment
bfxil x7, x27, 4, 16
# accumulate value for integer segment
lsl x7, x7, 16
bfxil x7, x28, 4, 16
# accumulate value for integer segment
lsl x7, x7, 16
bfxil x7, x15, 4, 16
# construct integer segment from accumulator
rev64 x7, x7
lsr x7, x7, 16
With this commit, the code is simplifed to:
# accumulate value for integer segment at offset 48
bfi x7, x27, 44, 20
# accumulate value for integer segment at offset 32
bfi x7, x28, 28, 20
# accumulate value for integer segment at offset 16
bfi x7, x15, 12, 20
# construct integer segment from accumulator
rev64 x7, x7
Simplify the code when right-hand side operand is constant. Also eliminate some register shuffling by using the LEA instruction.
Take better advantage of operand types. * If one operand is known to never be an immediate term, don't emit any test for immediate operands. (Just go ahead and call the helper fragment.) * Don't do any immediate test for known immediates.
* Inline equality test with lists of a single immediate element (such as `[42]` or `[a]`). Call a specialized helper fragment for equality test with lists of two or more immediates. * Call a a specialized helper fragment for matching tuples containing only immediates. Use the same helper fragment for matching bignums and floats. * Inline comparisons with empty binaries and empty maps.
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Take better advantage of type information and known constant operands to enhance code generation. Also take advantage of the bit manipulation instructions for AArch64 to enhance code generation for the binary syntax.