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Legalize imul.i64x2 for both AVX and non-AVX x86 CPUs #1759

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merged 9 commits into from
Jun 3, 2020
Merged

Legalize imul.i64x2 for both AVX and non-AVX x86 CPUs #1759

merged 9 commits into from
Jun 3, 2020

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abrown
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@abrown abrown commented May 26, 2020

The convert_i64x2_imul custom legalization checks the ISA flags for AVX512DQ or AVX512VL support and legalizes imul.i64x2 to an x86_pmullq in this case; if not, it uses a lengthy SSE2-compatible instruction sequence. For this logic to work, we need:

  • the AVX512 instruction to be defined as a separate Cranelift instruction, x86_pmullq (this additional instruction would go away in the new backend)
  • a mechanism for accessing the x86 TargetIsa so that we can inspect its flags during legalization
  • a new SSE2 instruction, x86_pmuludq for implementing the SSE2-compatible instruction sequence

@abrown abrown force-pushed the i64x2-mul branch 2 times, most recently from e48a82c to fdcfd1c Compare May 26, 2020 17:11
@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. labels May 26, 2020
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@abrown abrown mentioned this pull request May 26, 2020
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@abrown abrown marked this pull request as ready for review May 26, 2020 17:47
@abrown abrown requested a review from bnjbvr May 26, 2020 17:48
@abrown abrown mentioned this pull request May 26, 2020
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@abrown abrown force-pushed the i64x2-mul branch 2 times, most recently from 85cd9eb to 57cc3e2 Compare May 30, 2020 03:14
@whitequark whitequark mentioned this pull request May 30, 2020
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bnjbvr
bnjbvr reviewed Jun 2, 2020
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Looks pretty good! I wonder if the legalization couldn't be done in the meta-language directly using an ISA predicate (and thus avoiding the Any and downcasting).

cranelift/codegen/meta/src/isa/x86/instructions.rs Show resolved Hide resolved
cranelift/codegen/meta/src/isa/x86/instructions.rs Outdated Show resolved Hide resolved
cranelift/codegen/src/isa/x86/enc_tables.rs Outdated Show resolved Hide resolved
cranelift/codegen/src/isa/x86/enc_tables.rs Show resolved Hide resolved
cranelift/codegen/src/isa/x86/enc_tables.rs Show resolved Hide resolved
bnjbvr
bnjbvr approved these changes Jun 3, 2020
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Unless guarding-legalizations-against-ISA-settings is easy to implement, the proposed approach here works fine. Thanks for the patch!

@abrown
Add x86-specific instruction for i64x2 multiplication
e9640a1 
Without this special instruction, legalizing to the AVX512 instruction AND the SSE instruction sequence is impossible. This extra instruction would be rendered unnecessary by the x64 backend.
@abrown
Add TargetIsa::as_any for downcasting to specific ISA implementations
8092e9e 
This is necessary when we would like to check specific ISA flags, e.g.
@abrown
Add x86_pmuludq
669ff19 
This instruction multiplies the lower 32 bits of two 64x2 unsigned integers into an i64x2; this is necessary for lowering Wasm's i64x2.mul.
@abrown
Remove non-existent x86 encoding for sshr_imm.i64x2
7293736 
This instruction does not exist in the SSE2 feature set; it can be added later with an VEX/EVEX encoding.
@abrown
Re-organize transform groups for x86 legalization
a536aba
@abrown
Add x86 legalization for imul.i64x2 for non-AVX CPUs
77b22c9 
The `convert_i64x2_imul` custom legalization checks the ISA flags for AVX512DQ or AVX512VL support and legalizes `imul.i64x2` to an `x86_pmullq` in this case; if not, it uses a lengthy SSE2-compatible instruction sequence.
@abrown
Translate Wasm's I64x2Mul to Cranelift's imul.i64x2
4f52d69
@abrown
Enable SIMD spec test for i64x2 arithmetic
73a799d
@abrown
Rename opcode: PMULLQ to VPMULLQ
bb72621
@abrown abrown merged commit 5db384c into bytecodealliance:master Jun 3, 2020
@abrown abrown deleted the i64x2-mul branch June 3, 2020 23:28
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