YJIT: A64: Use ADDS/SUBS/CMP (immediate) when possible#10402
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maximecb merged 3 commits intoruby:masterfrom Apr 2, 2024
Merged
YJIT: A64: Use ADDS/SUBS/CMP (immediate) when possible#10402maximecb merged 3 commits intoruby:masterfrom
maximecb merged 3 commits intoruby:masterfrom
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We were loading 1 into a register and then doing ADDS/SUBS previously. That was particularly bad since those come up in fixnum operations. ```diff # integer left shift with rhs=1 - mov x11, #1 - subs x11, x1, x11 + subs x11, x1, #1 lsl x12, x11, #1 asr x13, x12, #1 cmp x13, x11 - b.ne #0x106ab60f8 - mov x11, #1 - adds x12, x12, x11 + b.ne #0x10903a0f8 + adds x12, x12, #1 mov x1, x12 ``` Note that it's fine to cast between i64 and u64 since the bit pattern is preserved, and the add/sub themselves don't care about the signedness of the operands. CMP is just another mnemonic for SUBS.
kddnewton
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Mar 28, 2024
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kddnewton
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You'll need to make sure every instruction it's passed to will handle this signature now.
There is in fact no MUL on A64 that takes an immediate, so this instruction was using the wrong split method. No current usages of this form in YJIT.
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Good find. There were some failing tests that don't seem related to this PR. Updating the branch to run the tests again. |
k0kubun
approved these changes
Apr 2, 2024
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We were loading 1 into a register and then doing ADDS/SUBS previously.
That was particularly bad since those come up in fixnum operations.