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Optimize "constant_string".Length #16898

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EgorBo wants to merge 4 commits into from
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Optimize "constant_string".Length #16898

EgorBo wants to merge 4 commits into from

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@EgorBo
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@EgorBo EgorBo commented Sep 17, 2019 •
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static int Test() => "Hello".Length; // replace with just `5`

Before:

movabs rax,0x7fd6c1758160
mov    eax,DWORD PTR [rax]
ret

Now:

mov    eax,0x5
ret

Also, handles cases after inlining, e.g.:

bool Validate(string str)
{
    return str.Length > 0 && str.Length <= 100;
}

bool Test()
{
    return Validate("Hello");  // Validate() will be inlined
}

New codegen for Test:

mov    eax, 1     ; return true
ret

I have a similar PR for CoreCLR: dotnet/runtime#1378
jit-diff report found >30k bytes of improvements.

@kg
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kg commented Sep 17, 2019

@monojenkins build failed

@akoeplinger
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akoeplinger commented Jan 23, 2020

/azp run sync-mono-to-runtime

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Azure Pipelines successfully started running 1 pipeline(s).

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@monojenkins monojenkins mentioned this pull request Jan 23, 2020
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vargaz
vargaz reviewed Jan 24, 2020
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mono/mini/decompose.c
MONO_EMIT_NEW_LOAD_MEMBASE_OP_FLAGS (cfg, OP_LOADI4_MEMBASE, ins->dreg,
ins->sreg1, MONO_STRUCT_OFFSET (MonoString, length), ins->flags | MONO_INST_INVARIANT_LOAD);
if (ins->prev && ins->prev->opcode == OP_I8CONST) {
// Optimize String.get_length for ldstr, e.g.:
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@vargaz vargaz Jan 24, 2020

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Need to check that ins->prev->dreg == ins->sreg1.

vargaz
vargaz reviewed Jan 24, 2020
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mono/mini/decompose.c
// Optimize String.get_length for ldstr, e.g.:
// "hello".Length => 5
mono_domain_lock(cfg->domain);
MonoGHashTable* table = cfg->domain->ldstr_table;
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@vargaz vargaz Jan 24, 2020

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Coding style.

@EgorBo EgorBo closed this Feb 20, 2020
@EgorBo EgorBo mentioned this pull request Oct 14, 2024
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@xtqqczze xtqqczze mentioned this pull request Oct 14, 2024
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@EgorBo @kg @akoeplinger @vargaz @JHHGVJH123