Stream: git-wasmtime

Topic: wasmtime / Issue #2489 [machinst x64]: implement load*_ze...

Wasmtime GitHub notifications bot (Dec 08 2020 at 16:59):

abrown commented on Issue #2489:

As mentioned on Zulip, this runs into issues. When I run RUST_LOG=cranelift_codegen=debug cargo run --features experimental_x64 -- wast --disable-cache --enable-simd scratch.wast on:

(module
  (memory 1)
  (data (i32.const 0) "\00\01\02\03\04\05\06\07\08\09\0A\0B\0C\0D\0E\0F\80\81\82\83\84\85\86\87\88\89")
  (data (i32.const 65520) "\0A\0B\0C\0D\0E\0F\80\81\82\83\84\85\86\87\88\89")
  (func (export "v128.load32_zero") (param $0 i32) (result v128)
    (v128.load32_zero (local.get $0))
  )
)
(assert_return (invoke "v128.load32_zero" (i32.const 0)) (v128.const i32x4 0x03020100 0x00000000 0x00000000 0x00000000))

The test fails with:

Error: failed to run script file 'scratch.wast'

Caused by:
    0: failed directive on scratch.wast:9:1
    1: expected V128(I32x4([50462976, 0, 0, 0])) (0x00000000000000000000000000010203), got V128(2595974132930443020774722140989752) (0x00007ffdccd1730000007ffdccd16938)

After lowering, the MOVSS is present (as it should be):

DEBUG cranelift_codegen::machinst::compile    > vcode from lowering:
VCode_ShowWithRRU {{
  Entry block: 0
Block 0:
  (original IR block: block0)
  (successor: Block 1)
  (instruction range: 0 .. 9)
  Inst 0:   movq    %rdi, %v0J
  Inst 1:   movq    %rsi, %v1J
  Inst 2:   movq    %rdx, %v2J
  Inst 3:   movl    %v2Jl, %v3Jl
  Inst 4:   movq    28(%v0J), %v4J
  Inst 5:   movl    0(%v4J,%v3J,1), %v6Jl
  Inst 6:   movss   %v6J, %v7V
  Inst 7:   movdqa  %v7V, %v8V
  Inst 8:   jmp     label1
Block 1:
  (original IR block: block1)
  (instruction range: 9 .. 12)
  Inst 9:   movdqa  %v8V, %v9V
  Inst 10:   movdqa  %v9V, %xmm0
  Inst 11:   ret
}}

But after regalloc it is gone!

DEBUG cranelift_codegen::machinst::compile    > vcode after regalloc: final version:
VCode_ShowWithRRU {{
  Entry block: 0
Block 0:
  (original IR block: block0)
  (successor: Block 1)
  (instruction range: 0 .. 6)
  Inst 0:   pushq   %rbp
  Inst 1:   movq    %rsp, %rbp
  Inst 2:   movl    %edx, %esi
  Inst 3:   movq    28(%rdi), %rdi
  Inst 4:   movl    0(%rdi,%rsi,1), %xmm0
  Inst 5:   jmp     label1
Block 1:
  (original IR block: block1)
  (instruction range: 6 .. 9)
  Inst 6:   movq    %rbp, %rsp
  Inst 7:   popq    %rbp
  Inst 8:   re

Wasmtime GitHub notifications bot (Jan 04 2021 at 20:10):

abrown commented on Issue #2489:

Weirdly, a CLIF filetest like the following will produce the expected code:

test compile
set enable_simd
target x86_64 has_ssse3 has_sse41
feature "experimental_x64"

function %load32_zero(i64) -> i32x4 {
block0(v0: i64):
    v1 = load.i32 v0
    v2 = scalar_to_vector.i32x4 v1
    ; check:  movss   0(%rdi), %xmm0
    return v2
}

When I run that with cargo run --features experimental_x64 -p cranelift-tools -- compile --target="x86_64" -dDp scratch.clif I see the following before regalloc:

 DEBUG cranelift_codegen::machinst::compile    > vcode from lowering:
VCode_ShowWithRRU {{
  Entry block: 0
Block 0:
  (original IR block: block0)
  (instruction range: 0 .. 5)
  Inst 0:   movq    %rdi, %v0J
  Inst 1:   movss   0(%v0J), %v2V
  Inst 2:   movdqa  %v2V, %v3V
  Inst 3:   movdqa  %v3V, %xmm0
  Inst 4:   ret
}}

And after, the correct MOVSS:

 DEBUG cranelift_codegen::machinst::compile    > vcode after regalloc: final version:
VCode_ShowWithRRU {{
  Entry block: 0
Block 0:
  (original IR block: block0)
  (instruction range: 0 .. 6)
  Inst 0:   pushq   %rbp
  Inst 1:   movq    %rsp, %rbp
  Inst 2:   movss   0(%rdi), %xmm0
  Inst 3:   movq    %rbp, %rsp
  Inst 4:   popq    %rbp
  Inst 5:   ret
}}

Wasmtime GitHub notifications bot (Jan 05 2021 at 00:35):

abrown commented on Issue #2489:

@cfallin, I am bringing this out of draft since:

• it seems like we are still merging x64 SIMD code despite the tests being disabled (I checked locally and this passes the tests)
• I think this side-steps most of the stuff we found in #2545, though we should still fix that separately.

Wasmtime GitHub notifications bot (Jan 05 2021 at 00:39):

cfallin commented on Issue #2489:

Will review soon; re: merging SIMD, yes, at least my position right now is that we should be able to keep making progress on SIMD despite the CI heisenbug and disabled tests; when we resolve that bug and turn the tests back on, we'll see any issues and be able to trace them back to one of N PRs merged recently. IMHO that's better than holding all SIMD work until we track down the issue, given that it's proven elusive so far.

Wasmtime GitHub notifications bot (Jan 09 2021 at 00:41):

cfallin commented on Issue #2489:

@abrown I think this broke the build on main as it went in after the multi-reg refactor but tests had run before it.

Last updated: Dec 23 2024 at 13:07 UTC