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cranelift: Remove the fcvt_low_from_sint instruction #6565

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This commit removes this instruction since it's a combination of swiden_low plus fcvt_from_sint. This was used by the WebAssembly f64x2.convert_low_i32x4_s instruction previously but the corresponding unsigned variant of the instruction, f64x2.convert_low_i32x4_u, used a uwiden_low plus fcvt_from_uint combo. To help simplify Cranelift's instruction set and to make these two instructions mirrors of each other the Cranelift instruction is removed.

The s390x and AArch64 backend lowering rules for this instruction could simply be deleted as the previous combination of the swiden_low and fcvt_from_sint lowering rules produces the same code. The x64 backend moved its lowering to a special case of the fcvt_from_sint lowering.

This commit removes this instruction since it's a combination of
`swiden_low` plus `fcvt_from_sint`. This was used by the WebAssembly
`f64x2.convert_low_i32x4_s` instruction previously but the corresponding
unsigned variant of the instruction, `f64x2.convert_low_i32x4_u`, used a
`uwiden_low` plus `fcvt_from_uint` combo. To help simplify Cranelift's
instruction set and to make these two instructions mirrors of each other
the Cranelift instruction is removed.

The s390x and AArch64 backend lowering rules for this instruction could
simply be deleted as the previous combination of the `swiden_low` and
`fcvt_from_sint` lowering rules produces the same code. The x64 backend
moved its lowering to a special case of the `fcvt_from_sint` lowering.
@alexcrichton alexcrichton requested a review from a team as a code owner June 12, 2023 20:30
@alexcrichton alexcrichton requested review from abrown and removed request for a team June 12, 2023 20:30
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It's always nice to get rid of CLIF instructions and this one looks to have been remarkably painless. Thank you!

@github-actions github-actions bot added cranelift Issues related to the Cranelift code generator cranelift:area:aarch64 Issues related to AArch64 backend. cranelift:area:x64 Issues related to x64 codegen cranelift:meta Everything related to the meta-language. cranelift:wasm labels Jun 12, 2023
@alexcrichton alexcrichton added this pull request to the merge queue Jun 12, 2023
@github-merge-queue github-merge-queue bot removed this pull request from the merge queue due to failed status checks Jun 12, 2023
@alexcrichton alexcrichton added this pull request to the merge queue Jun 13, 2023
Merged via the queue into bytecodealliance:main with commit 7f108b1 Jun 13, 2023
@alexcrichton alexcrichton deleted the remove-fcvt-low-from-sint branch June 13, 2023 01:12
salewski pushed a commit to salewski/wasmtime that referenced this pull request Jun 30, 2023
…nce#6565)

* cranelift: Remove the `fcvt_low_from_sint` instruction

This commit removes this instruction since it's a combination of
`swiden_low` plus `fcvt_from_sint`. This was used by the WebAssembly
`f64x2.convert_low_i32x4_s` instruction previously but the corresponding
unsigned variant of the instruction, `f64x2.convert_low_i32x4_u`, used a
`uwiden_low` plus `fcvt_from_uint` combo. To help simplify Cranelift's
instruction set and to make these two instructions mirrors of each other
the Cranelift instruction is removed.

The s390x and AArch64 backend lowering rules for this instruction could
simply be deleted as the previous combination of the `swiden_low` and
`fcvt_from_sint` lowering rules produces the same code. The x64 backend
moved its lowering to a special case of the `fcvt_from_sint` lowering.

* Fix cranelift-fuzzgen build
salewski pushed a commit to salewski/wasmtime that referenced this pull request Jun 30, 2023
…nce#6565)

* cranelift: Remove the `fcvt_low_from_sint` instruction

This commit removes this instruction since it's a combination of
`swiden_low` plus `fcvt_from_sint`. This was used by the WebAssembly
`f64x2.convert_low_i32x4_s` instruction previously but the corresponding
unsigned variant of the instruction, `f64x2.convert_low_i32x4_u`, used a
`uwiden_low` plus `fcvt_from_uint` combo. To help simplify Cranelift's
instruction set and to make these two instructions mirrors of each other
the Cranelift instruction is removed.

The s390x and AArch64 backend lowering rules for this instruction could
simply be deleted as the previous combination of the `swiden_low` and
`fcvt_from_sint` lowering rules produces the same code. The x64 backend
moved its lowering to a special case of the `fcvt_from_sint` lowering.

* Fix cranelift-fuzzgen build
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