Unroll StringBuilder.Append for const string by yesmey · Pull Request #85894 · dotnet/runtime

yesmey · 2023-05-07T23:08:16Z

Buffer.Memmove is now being unrolled for constant lengths. If we simplify Append(ref char, int) a bit, the JIT can inline it.
As a result, this allows the methods StringBuilder.Append(string) and StringBuilder.AppendLine() to be able to be unrolled.
I didn't seem to need to add any AggressiveInlining attribute, so I left it out.

Const string example

public static void Example(StringBuilder stringBuilder)
{
    stringBuilder.Append("1234567890abcdefghijklmnopqrstuvwxyzåäö");
}

Before:

; Method Program:Example(System.Text.StringBuilder)
G_M35345_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M35345_IG02:  ;; offset=0004H
       cmp      byte  ptr [rcx], cl
       mov      rdx, 0x154802028D8      ; '1'
       add      rdx, 12
       mov      r8d, 39
       call     [System.Text.StringBuilder:Append(byref,int):this]
       nop      
						;; size=29 bbWeight=1 PerfScore 7.00

G_M35345_IG03:  ;; offset=0021H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 38

After:

; Method Program:Example(System.Text.StringBuilder)
G_M35345_IG01:  ;; offset=0000H
       sub      rsp, 40
       vzeroupper 
						;; size=7 bbWeight=1 PerfScore 1.25

G_M35345_IG02:  ;; offset=0007H
       mov      rdx, 0x18C802028D8      ; '1'
       add      rdx, 12
       mov      r8, gword ptr [rcx+08H]
       mov      eax, dword ptr [rcx+18H]
       lea      r9d, [rax+27H]
       cmp      dword ptr [r8+08H], r9d
       jb       SHORT G_M35345_IG04
						;; size=31 bbWeight=1 PerfScore 9.00

G_M35345_IG03:  ;; offset=0026H
       movsxd   r9, eax
       lea      r8, bword ptr [r8+2*r9+10H]
       vmovdqu  ymm0, ymmword ptr [rdx]
       vmovdqu  ymm1, ymmword ptr [rdx+20H]
       vmovdqu  xmm2, xmmword ptr [rdx+3EH]
       vmovdqu  ymmword ptr [r8], ymm0
       vmovdqu  ymmword ptr [r8+20H], ymm1
       vmovdqu  xmmword ptr [r8+3EH], xmm2
       add      eax, 39
       mov      dword ptr [rcx+18H], eax
       jmp      SHORT G_M35345_IG05
						;; size=47 bbWeight=0.50 PerfScore 12.25

G_M35345_IG04:  ;; offset=0055H
       mov      r8d, 39
       call     [System.Text.StringBuilder:AppendWithExpansion(byref,int):this]
						;; size=12 bbWeight=0.50 PerfScore 1.62

G_M35345_IG05:  ;; offset=0061H
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M35345_IG06:  ;; offset=0062H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 103

AppendLine example

public static void Example(StringBuilder stringBuilder)
{
    stringBuilder.AppendLine();
}

Before:

; Method Program:Example(System.Text.StringBuilder)
G_M35345_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M35345_IG02:  ;; offset=0004H
       cmp      byte  ptr [rcx], cl
       mov      rdx, 0x195802028D8      ; '  '
       add      rdx, 12
       mov      r8d, 2
       call     [System.Text.StringBuilder:Append(byref,int):this]
       nop      
						;; size=29 bbWeight=1 PerfScore 7.00

G_M35345_IG03:  ;; offset=0021H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 38

After:

; Method Program:Example(System.Text.StringBuilder)
G_M35345_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M35345_IG02:  ;; offset=0004H
       mov      rdx, 0x17C002028D8      ; '  '
       add      rdx, 12
       mov      r8, gword ptr [rcx+08H]
       mov      eax, dword ptr [rcx+18H]
       lea      r9d, [rax+02H]
       cmp      dword ptr [r8+08H], r9d
       jb       SHORT G_M35345_IG04
						;; size=31 bbWeight=1 PerfScore 9.00

G_M35345_IG03:  ;; offset=0023H
       movsxd   r9, eax
       lea      r8, bword ptr [r8+2*r9+10H]
       mov      r9d, dword ptr [rdx]
       mov      dword ptr [r8], r9d
       add      eax, 2
       mov      dword ptr [rcx+18H], eax
       jmp      SHORT G_M35345_IG05
						;; size=22 bbWeight=0.50 PerfScore 3.75

G_M35345_IG04:  ;; offset=0039H
       mov      r8d, 2
       call     [System.Text.StringBuilder:AppendWithExpansion(byref,int):this]
						;; size=12 bbWeight=0.50 PerfScore 1.62

G_M35345_IG05:  ;; offset=0045H
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M35345_IG06:  ;; offset=0046H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 75

@EgorBo can you please take a look at this

EgorBo · 2023-05-07T23:27:47Z

Very nice use-case! One problem that it might slightly regress the case when it's not inlined and Mono.
The method seems to be compiled to a small codegen (when not unrolled) so presumably it won't hurt to mark it as AggressiveInlining.

Another option is to tune inliner - if it sees Buffer.Memmove and the last arg is a constant - boost inlining (but you need to invoke a different overload of Buffer.Memmove, the one that accepts byte)

EgorBo · 2023-05-07T23:50:28Z

EgorBo@b79af3f

this seems to be enough to make it inlineable for const input (it gives inliner extra hint)

yesmey · 2023-05-08T10:02:12Z

You are right we need to keep small size optimization, I figured it was only there for constant separators/newline, and I didn't think about Mono.

EgorBo@b79af3f

this seems to be enough to make it inlineable for const input (it gives inliner extra hint)

That's a cool trick! It seem to make it inline it pretty aggressively unfortunately, even when the input is not constant. It causes the code size to increase a lot where its not really necessary.

Another option is to tune inliner - if it sees Buffer.Memmove and the last arg is a constant - boost inlining (but you need to invoke a different overload of Buffer.Memmove, the one that accepts byte)

What's funny is that if I use the byte variant of Buffer.Memmove instead, it already seems to make it inlinable! (without removing the optimization for small input of course). I'm guessing directly calling an intrinsic gives an inline hint?

It seems to hit a pretty good spot now where it inlines for a constant length, but not otherwise.

I know very little about how the jit works, so I'm out of my league here - but is it possible an even better solution is to somehow make both variants of Buffer.Memmove have the same inlining "weight"? It feels a bit odd that they behave differently here.

yesmey · 2023-05-08T10:27:40Z

With current code:

public static void Example(StringBuilder builder, string s)
{
    builder.Append(s);
    builder.Append("1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN");
    builder.AppendLine();
}

; Method Program:Example(System.Text.StringBuilder,System.String)
G_M17123_IG01:  ;; offset=0000H
       push     rsi
       sub      rsp, 32
       vzeroupper 
       mov      rsi, rcx
						;; size=11 bbWeight=1 PerfScore 2.50

G_M17123_IG02:  ;; offset=000BH
       cmp      byte  ptr [rsi], sil
       test     rdx, rdx
       je       SHORT G_M17123_IG04
						;; size=8 bbWeight=1 PerfScore 4.25

G_M17123_IG03:  ;; offset=0013H
       mov      r8d, dword ptr [rdx+08H]
       add      rdx, 12
       mov      rcx, rsi
       call     [System.Text.StringBuilder:Append(byref,int):this]
						;; size=17 bbWeight=0.50 PerfScore 2.75

G_M17123_IG04:  ;; offset=0024H
       mov      rdx, 0x1EB802028D8      ; '1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN'
       add      rdx, 12
       mov      rcx, gword ptr [rsi+08H]
       mov      r8d, dword ptr [rsi+18H]
       lea      eax, [r8+32H]
       cmp      dword ptr [rcx+08H], eax
       jb       SHORT G_M17123_IG06
						;; size=31 bbWeight=1 PerfScore 9.00

G_M17123_IG05:  ;; offset=0043H
       movsxd   rax, r8d
       lea      rcx, bword ptr [rcx+2*rax+10H]
       vmovdqu  ymm0, ymmword ptr [rdx]
       vmovdqu  ymm1, ymmword ptr [rdx+20H]
       vmovdqu  ymm2, ymmword ptr [rdx+40H]
       vmovdqu  xmm3, xmmword ptr [rdx+54H]
       vmovdqu  ymmword ptr [rcx], ymm0
       vmovdqu  ymmword ptr [rcx+20H], ymm1
       vmovdqu  ymmword ptr [rcx+40H], ymm2
       vmovdqu  xmmword ptr [rcx+54H], xmm3
       add      r8d, 50
       mov      dword ptr [rsi+18H], r8d
       jmp      SHORT G_M17123_IG07
						;; size=56 bbWeight=0.50 PerfScore 15.75

G_M17123_IG06:  ;; offset=007BH
       mov      rcx, rsi
       mov      r8d, 50
       call     [System.Text.StringBuilder:AppendWithExpansion(byref,int):this]
						;; size=15 bbWeight=0.50 PerfScore 1.75

G_M17123_IG07:  ;; offset=008AH
       mov      rdx, 0x1EB80202958      ; '  '
       add      rdx, 12
       mov      rcx, gword ptr [rsi+08H]
       mov      r8d, dword ptr [rsi+18H]
       lea      eax, [r8+02H]
       cmp      dword ptr [rcx+08H], eax
       jb       SHORT G_M17123_IG09
						;; size=31 bbWeight=1 PerfScore 9.00

G_M17123_IG08:  ;; offset=00A9H
       movsxd   rdx, r8d
       lea      rcx, bword ptr [rcx+2*rdx+10H]
       mov      word  ptr [rcx], 13
       mov      word  ptr [rcx+02H], 10
       mov      dword ptr [rsi+18H], eax
       jmp      SHORT G_M17123_IG10
						;; size=24 bbWeight=0.50 PerfScore 3.12

G_M17123_IG09:  ;; offset=00C1H
       mov      rcx, rsi
       mov      r8d, 2
       call     [System.Text.StringBuilder:AppendWithExpansion(byref,int):this]
						;; size=15 bbWeight=0.50 PerfScore 1.75

G_M17123_IG10:  ;; offset=00D0H
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M17123_IG11:  ;; offset=00D1H
       add      rsp, 32
       pop      rsi
       ret      
						;; size=6 bbWeight=1 PerfScore 1.75
; Total bytes of code: 215

EgorBo · 2023-05-08T15:18:34Z

@yesmey can you apply this patch 47eb0eb

it allows us to avoid using uglier version of Memmove + possibly improves other similiar cases

yesmey · 2023-05-08T18:11:58Z

@yesmey can you apply this patch 47eb0eb

it allows us to avoid using uglier version of Memmove + possibly improves other similiar cases

Works perfectly for this scenario, thanks! I'll post some examples here. I assume you will want to take it from here and close this?

Append non-const

public static void Append(StringBuilder builder, string s)
{
    builder.Append(s);
}

Before

; Method Program:Append(System.Text.StringBuilder,System.String)
G_M43621_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M43621_IG02:  ;; offset=0004H
       cmp      byte  ptr [rcx], cl
       test     rdx, rdx
       je       SHORT G_M43621_IG04
						;; size=7 bbWeight=1 PerfScore 4.25

G_M43621_IG03:  ;; offset=000BH
       mov      r8d, dword ptr [rdx+08H]
       add      rdx, 12
       call     [System.Text.StringBuilder:Append(byref,int):this]
						;; size=14 bbWeight=0.49 PerfScore 2.57

G_M43621_IG04:  ;; offset=0019H
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M43621_IG05:  ;; offset=001AH
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 31

After

; Method Program:Append(System.Text.StringBuilder,System.String)
G_M43621_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M43621_IG02:  ;; offset=0004H
       cmp      byte  ptr [rcx], cl
       test     rdx, rdx
       je       SHORT G_M43621_IG04
						;; size=7 bbWeight=1 PerfScore 4.25

G_M43621_IG03:  ;; offset=000BH
       mov      r8d, dword ptr [rdx+08H]
       add      rdx, 12
       call     [System.Text.StringBuilder:Append(byref,int):this]
						;; size=14 bbWeight=0.50 PerfScore 2.62

G_M43621_IG04:  ;; offset=0019H
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M43621_IG05:  ;; offset=001AH
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 31

Append by index non-const

public static void AppendIndex(StringBuilder builder, string s)
{
    builder.Append(s, 2, 16);
}

Before

; Method Program:AppendIndex(System.Text.StringBuilder,System.String)
G_M19771_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M19771_IG02:  ;; offset=0004H
       mov      r8d, 2
       mov      r9d, 16
       cmp      dword ptr [rcx], ecx
       call     [System.Text.StringBuilder:Append(System.String,int,int):System.Text.StringBuilder:this]
       nop      
						;; size=21 bbWeight=1 PerfScore 6.75

G_M19771_IG03:  ;; offset=0019H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 30

After

; Method Program:AppendIndex(System.Text.StringBuilder,System.String)
G_M19771_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M19771_IG02:  ;; offset=0004H
       mov      r8d, 2
       mov      r9d, 16
       cmp      dword ptr [rcx], ecx
       call     [System.Text.StringBuilder:Append(System.String,int,int):System.Text.StringBuilder:this]
       nop      
						;; size=21 bbWeight=1 PerfScore 6.75

G_M19771_IG03:  ;; offset=0019H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 30

AppendLine

public static void AppendLine(StringBuilder builder, string s)
{
    builder.AppendLine(s);
}

Before

; Method Program:AppendLine(System.Text.StringBuilder,System.String)
G_M48267_IG01:  ;; offset=0000H
       push     rsi
       sub      rsp, 32
       mov      rsi, rcx
						;; size=8 bbWeight=1 PerfScore 1.50

G_M48267_IG02:  ;; offset=0008H
       cmp      byte  ptr [rsi], sil
       test     rdx, rdx
       je       SHORT G_M48267_IG04
						;; size=8 bbWeight=1 PerfScore 4.25

G_M48267_IG03:  ;; offset=0010H
       mov      r8d, dword ptr [rdx+08H]
       add      rdx, 12
       mov      rcx, rsi
       call     [System.Text.StringBuilder:Append(byref,int):this]
						;; size=17 bbWeight=0.49 PerfScore 2.70

G_M48267_IG04:  ;; offset=0021H
       mov      rdx, 0x283002028D8      ; '  '
       add      rdx, 12
       mov      rcx, rsi
       mov      r8d, 2
       call     [System.Text.StringBuilder:Append(byref,int):this]
       nop      
						;; size=30 bbWeight=1 PerfScore 4.25

G_M48267_IG05:  ;; offset=003FH
       add      rsp, 32
       pop      rsi
       ret      
						;; size=6 bbWeight=1 PerfScore 1.75
; Total bytes of code: 69

After

; Method Program:AppendLine(System.Text.StringBuilder,System.String)
G_M48267_IG01:  ;; offset=0000H
       push     rsi
       sub      rsp, 32
       mov      rsi, rcx
						;; size=8 bbWeight=1 PerfScore 1.50

G_M48267_IG02:  ;; offset=0008H
       cmp      byte  ptr [rsi], sil
       test     rdx, rdx
       je       SHORT G_M48267_IG04
						;; size=8 bbWeight=1 PerfScore 4.25

G_M48267_IG03:  ;; offset=0010H
       mov      r8d, dword ptr [rdx+08H]
       add      rdx, 12
       mov      rcx, rsi
       call     [System.Text.StringBuilder:Append(byref,int):this]
						;; size=17 bbWeight=0.50 PerfScore 2.75

G_M48267_IG04:  ;; offset=0021H
       mov      rdx, 0x207003028D8      ; '  '
       add      rdx, 12
       mov      rcx, gword ptr [rsi+08H]
       mov      r8d, dword ptr [rsi+18H]
       lea      eax, [r8+02H]
       cmp      dword ptr [rcx+08H], eax
       jb       SHORT G_M48267_IG06
						;; size=31 bbWeight=1 PerfScore 9.00

G_M48267_IG05:  ;; offset=0040H
       movsxd   rdx, r8d
       lea      rcx, bword ptr [rcx+2*rdx+10H]
       mov      word  ptr [rcx], 13
       mov      word  ptr [rcx+02H], 10
       mov      dword ptr [rsi+18H], eax
       jmp      SHORT G_M48267_IG07
						;; size=24 bbWeight=0.50 PerfScore 3.12

G_M48267_IG06:  ;; offset=0058H
       mov      rcx, rsi
       mov      r8d, 2
       call     [System.Text.StringBuilder:AppendWithExpansion(byref,int):this]
						;; size=15 bbWeight=0.50 PerfScore 1.75

G_M48267_IG07:  ;; offset=0067H
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M48267_IG08:  ;; offset=0068H
       add      rsp, 32
       pop      rsi
       ret      
						;; size=6 bbWeight=1 PerfScore 1.75
; Total bytes of code: 110

Append const

public static void AppendConst(StringBuilder builder)
{
    builder.Append("1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN");
}

Before

; Method Program:AppendConst(System.Text.StringBuilder)
G_M5650_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M5650_IG02:  ;; offset=0004H
       cmp      byte  ptr [rcx], cl
       mov      rdx, 0x14A003028D8      ; '1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN'
       add      rdx, 12
       mov      r8d, 50
       call     [System.Text.StringBuilder:Append(byref,int):this]
       nop      
						;; size=29 bbWeight=1 PerfScore 7.00

G_M5650_IG03:  ;; offset=0021H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 38

After

; Method Program:AppendConst(System.Text.StringBuilder)
G_M5650_IG01:  ;; offset=0000H
       sub      rsp, 40
       vzeroupper 
						;; size=7 bbWeight=1 PerfScore 1.25

G_M5650_IG02:  ;; offset=0007H
       mov      rdx, 0x20B002028D8      ; '1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN'
       add      rdx, 12
       mov      r8, gword ptr [rcx+08H]
       mov      eax, dword ptr [rcx+18H]
       lea      r9d, [rax+32H]
       cmp      dword ptr [r8+08H], r9d
       jb       SHORT G_M5650_IG04
						;; size=31 bbWeight=1 PerfScore 9.00

G_M5650_IG03:  ;; offset=0026H
       movsxd   r9, eax
       lea      r8, bword ptr [r8+2*r9+10H]
       vmovdqu  ymm0, ymmword ptr [rdx]
       vmovdqu  ymm1, ymmword ptr [rdx+20H]
       vmovdqu  ymm2, ymmword ptr [rdx+40H]
       vmovdqu  xmm3, xmmword ptr [rdx+54H]
       vmovdqu  ymmword ptr [r8], ymm0
       vmovdqu  ymmword ptr [r8+20H], ymm1
       vmovdqu  ymmword ptr [r8+40H], ymm2
       vmovdqu  xmmword ptr [r8+54H], xmm3
       add      eax, 50
       mov      dword ptr [rcx+18H], eax
       jmp      SHORT G_M5650_IG05
						;; size=58 bbWeight=0.50 PerfScore 15.75

G_M5650_IG04:  ;; offset=0060H
       mov      r8d, 50
       call     [System.Text.StringBuilder:AppendWithExpansion(byref,int):this]
						;; size=12 bbWeight=0.50 PerfScore 1.62

G_M5650_IG05:  ;; offset=006CH
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M5650_IG06:  ;; offset=006DH
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 114

Append by index const

public static void AppendConstIndex(StringBuilder builder)
{
    builder.Append("1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN", 2, 16);
}

Before

; Method Program:AppendConstIndex(System.Text.StringBuilder)
G_M5612_IG01:  ;; offset=0000H
       sub      rsp, 40
       vzeroupper 
						;; size=7 bbWeight=1 PerfScore 1.25

G_M5612_IG02:  ;; offset=0007H
       mov      rdx, 0x257002028D8      ; '1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN'
       add      rdx, 12
       add      rdx, 4
       mov      r8, gword ptr [rcx+08H]
       mov      eax, dword ptr [rcx+18H]
       lea      r9d, [rax+10H]
       cmp      dword ptr [r8+08H], r9d
       jb       SHORT G_M5612_IG04
						;; size=35 bbWeight=1 PerfScore 9.25

G_M5612_IG03:  ;; offset=002AH
       movsxd   r9, eax
       lea      r8, bword ptr [r8+2*r9+10H]
       vmovdqu  ymm0, ymmword ptr [rdx]
       vmovdqu  ymmword ptr [r8], ymm0
       add      eax, 16
       mov      dword ptr [rcx+18H], eax
       jmp      SHORT G_M5612_IG05
						;; size=25 bbWeight=0.50 PerfScore 5.75

G_M5612_IG04:  ;; offset=0043H
       mov      r8d, 16
       call     [System.Text.StringBuilder:AppendWithExpansion(byref,int):this]
						;; size=12 bbWeight=0.50 PerfScore 1.62

G_M5612_IG05:  ;; offset=004FH
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M5612_IG06:  ;; offset=0050H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 85

After

; Method Program:AppendConstIndex(System.Text.StringBuilder)
G_M5612_IG01:  ;; offset=0000H
       sub      rsp, 40
       vzeroupper 
						;; size=7 bbWeight=1 PerfScore 1.25

G_M5612_IG02:  ;; offset=0007H
       mov      rdx, 0x18E802028D8      ; '1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN'
       add      rdx, 12
       add      rdx, 4
       mov      r8, gword ptr [rcx+08H]
       mov      eax, dword ptr [rcx+18H]
       lea      r9d, [rax+10H]
       cmp      dword ptr [r8+08H], r9d
       jb       SHORT G_M5612_IG04
						;; size=35 bbWeight=1 PerfScore 9.25

G_M5612_IG03:  ;; offset=002AH
       movsxd   r9, eax
       lea      r8, bword ptr [r8+2*r9+10H]
       vmovdqu  ymm0, ymmword ptr [rdx]
       vmovdqu  ymmword ptr [r8], ymm0
       add      eax, 16
       mov      dword ptr [rcx+18H], eax
       jmp      SHORT G_M5612_IG05
						;; size=25 bbWeight=0.50 PerfScore 5.75

G_M5612_IG04:  ;; offset=0043H
       mov      r8d, 16
       call     [System.Text.StringBuilder:AppendWithExpansion(byref,int):this]
						;; size=12 bbWeight=0.50 PerfScore 1.62

G_M5612_IG05:  ;; offset=004FH
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M5612_IG06:  ;; offset=0050H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 85

EgorBo · 2023-05-08T18:13:14Z

I assume you will want to take it from here and close this?

Feel free to integrate into your PR so we can merge it

EgorBo

Thanks for noticing the opportunity!

ghost · 2023-05-09T15:13:35Z

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

Issue Details

Buffer.Memmove is now being unrolled for constant lengths. If we simplify Append(ref char, int) a bit, the JIT can inline it.
As a result, this allows the methods StringBuilder.Append(string) and StringBuilder.AppendLine() to be able to be unrolled.
I didn't seem to need to add any AggressiveInlining attribute, so I left it out.

Const string example

public static void Example(StringBuilder stringBuilder)
{
    stringBuilder.Append("1234567890abcdefghijklmnopqrstuvwxyzåäö");
}

Before:

; Method Program:Example(System.Text.StringBuilder)
G_M35345_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M35345_IG02:  ;; offset=0004H
       cmp      byte  ptr [rcx], cl
       mov      rdx, 0x154802028D8      ; '1'
       add      rdx, 12
       mov      r8d, 39
       call     [System.Text.StringBuilder:Append(byref,int):this]
       nop      
						;; size=29 bbWeight=1 PerfScore 7.00

G_M35345_IG03:  ;; offset=0021H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 38

After:

; Method Program:Example(System.Text.StringBuilder)
G_M35345_IG01:  ;; offset=0000H
       sub      rsp, 40
       vzeroupper 
						;; size=7 bbWeight=1 PerfScore 1.25

G_M35345_IG02:  ;; offset=0007H
       mov      rdx, 0x18C802028D8      ; '1'
       add      rdx, 12
       mov      r8, gword ptr [rcx+08H]
       mov      eax, dword ptr [rcx+18H]
       lea      r9d, [rax+27H]
       cmp      dword ptr [r8+08H], r9d
       jb       SHORT G_M35345_IG04
						;; size=31 bbWeight=1 PerfScore 9.00

G_M35345_IG03:  ;; offset=0026H
       movsxd   r9, eax
       lea      r8, bword ptr [r8+2*r9+10H]
       vmovdqu  ymm0, ymmword ptr [rdx]
       vmovdqu  ymm1, ymmword ptr [rdx+20H]
       vmovdqu  xmm2, xmmword ptr [rdx+3EH]
       vmovdqu  ymmword ptr [r8], ymm0
       vmovdqu  ymmword ptr [r8+20H], ymm1
       vmovdqu  xmmword ptr [r8+3EH], xmm2
       add      eax, 39
       mov      dword ptr [rcx+18H], eax
       jmp      SHORT G_M35345_IG05
						;; size=47 bbWeight=0.50 PerfScore 12.25

G_M35345_IG04:  ;; offset=0055H
       mov      r8d, 39
       call     [System.Text.StringBuilder:AppendWithExpansion(byref,int):this]
						;; size=12 bbWeight=0.50 PerfScore 1.62

G_M35345_IG05:  ;; offset=0061H
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M35345_IG06:  ;; offset=0062H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 103

AppendLine example

public static void Example(StringBuilder stringBuilder)
{
    stringBuilder.AppendLine();
}

Before:

; Method Program:Example(System.Text.StringBuilder)
G_M35345_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M35345_IG02:  ;; offset=0004H
       cmp      byte  ptr [rcx], cl
       mov      rdx, 0x195802028D8      ; '  '
       add      rdx, 12
       mov      r8d, 2
       call     [System.Text.StringBuilder:Append(byref,int):this]
       nop      
						;; size=29 bbWeight=1 PerfScore 7.00

G_M35345_IG03:  ;; offset=0021H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 38

After:

; Method Program:Example(System.Text.StringBuilder)
G_M35345_IG01:  ;; offset=0000H
       sub      rsp, 40
						;; size=4 bbWeight=1 PerfScore 0.25

G_M35345_IG02:  ;; offset=0004H
       mov      rdx, 0x17C002028D8      ; '  '
       add      rdx, 12
       mov      r8, gword ptr [rcx+08H]
       mov      eax, dword ptr [rcx+18H]
       lea      r9d, [rax+02H]
       cmp      dword ptr [r8+08H], r9d
       jb       SHORT G_M35345_IG04
						;; size=31 bbWeight=1 PerfScore 9.00

G_M35345_IG03:  ;; offset=0023H
       movsxd   r9, eax
       lea      r8, bword ptr [r8+2*r9+10H]
       mov      r9d, dword ptr [rdx]
       mov      dword ptr [r8], r9d
       add      eax, 2
       mov      dword ptr [rcx+18H], eax
       jmp      SHORT G_M35345_IG05
						;; size=22 bbWeight=0.50 PerfScore 3.75

G_M35345_IG04:  ;; offset=0039H
       mov      r8d, 2
       call     [System.Text.StringBuilder:AppendWithExpansion(byref,int):this]
						;; size=12 bbWeight=0.50 PerfScore 1.62

G_M35345_IG05:  ;; offset=0045H
       nop      
						;; size=1 bbWeight=1 PerfScore 0.25

G_M35345_IG06:  ;; offset=0046H
       add      rsp, 40
       ret      
						;; size=5 bbWeight=1 PerfScore 1.25
; Total bytes of code: 75

@EgorBo can you please take a look at this

Author:	yesmey
Assignees:	-
Labels:	`area-CodeGen-coreclr`, `community-contribution`
Milestone:	-

EgorBo · 2023-05-09T15:14:14Z

@AndyAyersMS PTAL inliner change

AndyAyersMS

LGTM

EgorBo · 2023-05-11T14:33:04Z

Performance improvements on arm64:

[Perf] Windows/arm64: 5 Improvements on 5/9/2023 6:35:22 PM perf-autofiling-issues#17665
[Perf] Windows/arm64: 9 Improvements on 5/9/2023 6:35:22 PM perf-autofiling-issues#17921

sebastienros · 2023-05-11T21:13:06Z

This apparently is regressing Fortunes benchmarks with middleware in aspnet.

#86113

EgorBo · 2023-05-11T21:23:06Z

This apparently is regressing Fortunes benchmarks with middleware in aspnet.

#86113

Yes, this PR introduces more unrollings => more avx512 usages => throttle

This and other regressions are expected to be fixed by #85551

sebastienros · 2023-05-11T21:24:34Z

Thanks! The one that keeps giving. Makes sense since I couldn't repro the regression on the newer machines (aspnet-perf-lin).

Unroll StringBuilder.Append

bf015a3

ghost added needs-area-label An area label is needed to ensure this gets routed to the appropriate area owners community-contribution Indicates that the PR has been added by a community member labels May 7, 2023

Use byte memmove

876e644

EgorBo and others added 2 commits May 8, 2023 19:41

JIT: Boost inlining if we can unroll memmove/memcmp

7de305c

Revert old fix

b3b3219

EgorBo reviewed May 8, 2023

View reviewed changes

Comment thread src/libraries/System.Private.CoreLib/src/System/Text/StringBuilder.cs Outdated

EgorBo approved these changes May 8, 2023

View reviewed changes

Revert null check

e4678cb

EgorBo added area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI and removed needs-area-label An area label is needed to ensure this gets routed to the appropriate area owners labels May 9, 2023

EgorBo requested a review from AndyAyersMS May 9, 2023 15:14

AndyAyersMS approved these changes May 9, 2023

View reviewed changes

EgorBo merged commit 58a1365 into dotnet:main May 9, 2023

yesmey deleted the unroll-stringbuilder branch May 9, 2023 18:11

This was referenced May 11, 2023

Improve IndexOfAnyValues throughput for needles with 0 #84184

Merged

Regression on INTEL machines with TechEmpower Fortunes #86113

Closed

JulieLeeMSFT mentioned this pull request Jun 9, 2023

What's new in .NET 8 Preview 5 [WIP] dotnet/core#8436

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3 tasks

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