[mono][interp] Intrinsify BitOperations.Log2 #40069
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Tagging subscribers to this area: @BrzVlad |
| @@ -5358,6 +5358,16 @@ interp_exec_method (InterpFrame *frame, ThreadContext *context, FrameClauseArgs | |||
| ip++; | |||
| MINT_IN_BREAK; | |||
| } | |||
| MINT_IN_CASE(MINT_INTRINS_BITOPS_LOG2_32) { | |||
| sp [-1].data.i = 31 ^ (gint32)__builtin_clz ((guint32)sp [-1].data.i | 1); | |||
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__builtin_clz uses bsr since we don't set -march=native or -mattr+ https://godbolt.org/z/bMqcM5
lzcnt makes it even faster.
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This might need an ifdef gcc or something.
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@vargaz works fine on clang and should be correctly expanded for Arm
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With MSVC, we can use _BitScan{Forward,Reverse} with this conversion. (can be wrapped in a macro?)
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@EgorBo you could extract sgen_clz out of sgen into utils and reuse it here. We have the logic there to use _BitScan on msvc
ghost
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It's used in NumberFormatter, Array.Sort and SpanHelpers.
e.g. the following code uses it under the hood:
235235235325.ToString("X")^ For Mono-Wasm:
before: 18.4 ms (in a loop)
after: 15.2 ms