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optimize slice::Iter::next_chunk - #149131
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| .$array_ref(); // must convert &[T; N] to [&T; N] | ||
| Ok(r) | ||
| } else { | ||
| // cant use copy_nonoverlapping due to sadness |
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…unk, r=Mark-Simulacrum optimize `slice::Iter::next_chunk` codegen for example (sourced from rust-lang#98326 (comment)) ```rust pub fn simd_sum_slow(arr: &[u32]) -> u32 { const STEP_SIZE: usize = 16; let mut result = [0; STEP_SIZE]; let mut iter = arr.iter(); while let Ok(c) = iter.next_chunk::<STEP_SIZE>() { for (&n, r) in c.iter().zip(result.iter_mut()) { *r += n; } } result.iter().sum() } ``` goes from (znver4) <details> <summary>many asm</summary> ```assembly simd_sum_slow: .cfi_startproc push rbp .cfi_def_cfa_offset 16 push r15 .cfi_def_cfa_offset 24 push r14 .cfi_def_cfa_offset 32 push r13 .cfi_def_cfa_offset 40 push r12 .cfi_def_cfa_offset 48 push rbx .cfi_def_cfa_offset 56 sub rsp, 240 .cfi_def_cfa_offset 296 .cfi_offset rbx, -56 .cfi_offset r12, -48 .cfi_offset r13, -40 .cfi_offset r14, -32 .cfi_offset r15, -24 .cfi_offset rbp, -16 lea r12, [rdi + 4*rsi] mov qword ptr [rsp - 32], 0 mov dword ptr [rsp - 88], 0 mov dword ptr [rsp - 100], 0 mov dword ptr [rsp - 72], 0 mov dword ptr [rsp - 96], 0 mov dword ptr [rsp - 92], 0 mov dword ptr [rsp - 52], 0 mov dword ptr [rsp - 84], 0 mov dword ptr [rsp - 80], 0 mov dword ptr [rsp - 76], 0 mov dword ptr [rsp - 44], 0 mov dword ptr [rsp - 68], 0 mov dword ptr [rsp - 64], 0 mov dword ptr [rsp - 60], 0 mov dword ptr [rsp - 56], 0 mov dword ptr [rsp - 48], 0 mov qword ptr [rsp + 224], r12 cmp rdi, r12 mov qword ptr [rsp + 96], rdi je .LBB12_2 .p2align 4 .LBB12_3: lea r13, [rdi + 4] cmp r13, r12 je .LBB12_4 lea r15, [rdi + 8] cmp r15, r12 je .LBB12_6 lea r14, [rdi + 12] cmp r14, r12 je .LBB12_8 lea rbx, [rdi + 16] cmp rbx, r12 je .LBB12_10 lea r11, [rdi + 20] cmp r11, r12 je .LBB12_12 lea r10, [rdi + 24] cmp r10, r12 je .LBB12_14 lea r9, [rdi + 28] cmp r9, r12 je .LBB12_16 lea r8, [rdi + 32] cmp r8, r12 je .LBB12_18 lea rax, [rdi + 36] cmp rax, r12 je .LBB12_20 mov qword ptr [rsp - 120], rax lea rax, [rdi + 40] mov qword ptr [rsp - 112], rax cmp rax, r12 je .LBB12_22 lea rdx, [rdi + 44] cmp rdx, r12 je .LBB12_24 lea rbp, [rdi + 48] cmp rbp, r12 je .LBB12_26 mov qword ptr [rsp - 40], r9 lea rcx, [rdi + 52] cmp rcx, r12 je .LBB12_30 lea r9, [rdi + 56] cmp r9, r12 je .LBB12_32 lea rax, [rdi + 60] cmp rax, r12 mov qword ptr [rsp - 24], r9 je .LBB12_34 mov qword ptr [rsp + 88], rax lea rax, [rdi + 64] mov qword ptr [rsp - 8], rax mov dword ptr [rsp - 128], 0 mov qword ptr [rsp - 16], rdi mov qword ptr [rsp + 56], r10 lea r10, [rsp + 216] mov qword ptr [rsp + 40], r10 mov qword ptr [rsp + 96], r13 lea rax, [rsp + 208] mov qword ptr [rsp + 32], rax mov qword ptr [rsp + 72], rdx lea rsi, [rsp + 200] mov qword ptr [rsp + 48], rbx lea rbx, [rsp + 192] mov qword ptr [rsp + 80], rcx lea rcx, [rsp + 184] mov qword ptr [rsp + 64], rbp lea rdx, [rsp + 176] mov qword ptr [rsp + 16], r14 lea r14, [rsp + 168] mov qword ptr [rsp + 24], r11 lea r11, [rsp + 160] lea r9, [rsp + 152] lea r12, [rsp + 144] lea r13, [rsp + 136] lea rbp, [rsp + 128] mov qword ptr [rsp], r15 lea r15, [rsp + 120] mov qword ptr [rsp + 8], r8 lea r8, [rsp + 112] lea rdi, [rsp + 104] jmp .LBB12_39 .p2align 4 .LBB12_2: mov qword ptr [rsp - 128], 0 jmp .LBB12_37 .p2align 4 .LBB12_4: mov eax, 1 mov qword ptr [rsp - 128], rax jmp .LBB12_37 .p2align 4 .LBB12_6: mov eax, 2 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_8: mov eax, 3 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_10: mov eax, 4 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_12: mov eax, 5 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_14: mov eax, 6 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_16: mov eax, 7 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_18: mov eax, 8 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_20: mov eax, 9 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_22: mov eax, 10 mov qword ptr [rsp - 128], rax mov rdi, qword ptr [rsp - 120] jmp .LBB12_36 .LBB12_24: mov eax, 11 mov qword ptr [rsp - 128], rax jmp .LBB12_27 .LBB12_26: mov eax, 12 mov qword ptr [rsp - 128], rax .LBB12_27: mov rsi, qword ptr [rsp - 112] mov rdi, qword ptr [rsp - 120] jmp .LBB12_36 .LBB12_30: mov rcx, rbp mov eax, 13 mov qword ptr [rsp - 128], rax jmp .LBB12_35 .LBB12_32: mov rax, rcx mov rcx, rbp mov esi, 14 mov qword ptr [rsp - 128], rsi jmp .LBB12_35 .LBB12_34: mov rax, rcx mov rcx, rbp mov esi, 15 mov qword ptr [rsp - 128], rsi .LBB12_35: mov rsi, qword ptr [rsp - 112] mov rdi, qword ptr [rsp - 120] mov r9, qword ptr [rsp - 40] .p2align 4 .LBB12_36: mov rbp, r13 .LBB12_37: mov r13, qword ptr [rsp - 24] mov qword ptr [rsp + 88], r13 mov r13, qword ptr [rsp - 128] mov qword ptr [rsp + 216], r13 mov r13b, 1 mov dword ptr [rsp - 128], r13d mov qword ptr [rsp - 24], rax mov qword ptr [rsp + 80], rcx mov qword ptr [rsp + 64], rdx mov qword ptr [rsp + 72], rsi mov qword ptr [rsp - 112], rdi mov qword ptr [rsp - 120], r8 mov qword ptr [rsp + 8], r9 mov qword ptr [rsp - 40], r10 mov qword ptr [rsp + 56], r11 mov qword ptr [rsp + 24], rbx mov qword ptr [rsp + 48], r14 mov qword ptr [rsp + 16], r15 mov qword ptr [rsp], rbp mov eax, 0 mov qword ptr [rsp - 16], rax mov qword ptr [rsp - 8], r12 lea r10, [rsp + 208] mov qword ptr [rsp + 40], r10 lea rax, [rsp + 200] mov qword ptr [rsp + 32], rax lea rsi, [rsp + 192] lea rbx, [rsp + 184] lea rcx, [rsp + 176] lea rdx, [rsp + 168] lea r14, [rsp + 160] lea r11, [rsp + 152] lea r9, [rsp + 144] lea r12, [rsp + 136] lea r13, [rsp + 128] lea rbp, [rsp + 120] lea r15, [rsp + 112] lea r8, [rsp + 104] lea rdi, [rsp + 232] .LBB12_39: mov r10, qword ptr [rsp + 96] mov rax, qword ptr [rsp + 40] mov qword ptr [rax], r10 mov rax, qword ptr [rsp + 32] mov r10, qword ptr [rsp] mov qword ptr [rax], r10 mov rax, qword ptr [rsp + 16] mov qword ptr [rsi], rax mov rax, qword ptr [rsp + 48] mov qword ptr [rbx], rax mov rax, qword ptr [rsp + 24] mov qword ptr [rcx], rax mov rax, qword ptr [rsp + 56] mov qword ptr [rdx], rax mov rax, qword ptr [rsp - 40] mov qword ptr [r14], rax mov rax, qword ptr [rsp + 8] mov qword ptr [r11], rax mov rax, qword ptr [rsp - 120] mov qword ptr [r9], rax mov rax, qword ptr [rsp - 112] mov qword ptr [r12], rax mov rax, qword ptr [rsp + 72] mov qword ptr [r13], rax mov rax, qword ptr [rsp + 64] mov qword ptr [rbp], rax mov rax, qword ptr [rsp + 80] mov qword ptr [r15], rax mov rax, qword ptr [rsp - 24] mov qword ptr [r8], rax mov rax, qword ptr [rsp + 88] mov qword ptr [rdi], rax cmp byte ptr [rsp - 128], 0 jne .LBB12_40 mov rax, qword ptr [rsp - 32] mov rcx, qword ptr [rsp - 16] add eax, dword ptr [rcx] mov qword ptr [rsp - 32], rax mov rax, qword ptr [rsp + 216] mov ecx, dword ptr [rsp - 88] add ecx, dword ptr [rax] mov dword ptr [rsp - 88], ecx mov rax, qword ptr [rsp + 208] mov ecx, dword ptr [rsp - 100] add ecx, dword ptr [rax] mov dword ptr [rsp - 100], ecx mov rax, qword ptr [rsp + 200] mov ecx, dword ptr [rsp - 72] add ecx, dword ptr [rax] mov dword ptr [rsp - 72], ecx mov rax, qword ptr [rsp + 192] mov ecx, dword ptr [rsp - 96] add ecx, dword ptr [rax] mov dword ptr [rsp - 96], ecx mov rax, qword ptr [rsp + 184] mov ecx, dword ptr [rsp - 92] add ecx, dword ptr [rax] mov dword ptr [rsp - 92], ecx mov rax, qword ptr [rsp + 176] mov ecx, dword ptr [rsp - 52] add ecx, dword ptr [rax] mov dword ptr [rsp - 52], ecx mov rax, qword ptr [rsp + 168] mov ecx, dword ptr [rsp - 84] add ecx, dword ptr [rax] mov dword ptr [rsp - 84], ecx mov rax, qword ptr [rsp + 160] mov ecx, dword ptr [rsp - 80] add ecx, dword ptr [rax] mov dword ptr [rsp - 80], ecx mov rax, qword ptr [rsp + 152] mov ecx, dword ptr [rsp - 76] add ecx, dword ptr [rax] mov dword ptr [rsp - 76], ecx mov rax, qword ptr [rsp + 144] mov ecx, dword ptr [rsp - 44] add ecx, dword ptr [rax] mov dword ptr [rsp - 44], ecx mov rax, qword ptr [rsp + 136] mov ecx, dword ptr [rsp - 68] add ecx, dword ptr [rax] mov dword ptr [rsp - 68], ecx mov rax, qword ptr [rsp + 128] mov ecx, dword ptr [rsp - 64] add ecx, dword ptr [rax] mov dword ptr [rsp - 64], ecx mov rax, qword ptr [rsp + 120] mov ecx, dword ptr [rsp - 60] add ecx, dword ptr [rax] mov dword ptr [rsp - 60], ecx mov rax, qword ptr [rsp + 112] mov ecx, dword ptr [rsp - 56] add ecx, dword ptr [rax] mov dword ptr [rsp - 56], ecx mov rax, qword ptr [rsp + 104] mov ecx, dword ptr [rsp - 48] add ecx, dword ptr [rax] mov dword ptr [rsp - 48], ecx mov rdi, qword ptr [rsp - 8] mov r12, qword ptr [rsp + 224] cmp rdi, r12 mov qword ptr [rsp + 96], rdi jne .LBB12_3 jmp .LBB12_2 .LBB12_40: mov eax, dword ptr [rsp - 88] add eax, dword ptr [rsp - 32] mov ecx, dword ptr [rsp - 72] add ecx, dword ptr [rsp - 100] add ecx, eax mov edx, dword ptr [rsp - 92] add edx, dword ptr [rsp - 96] mov eax, dword ptr [rsp - 52] add eax, edx add eax, ecx mov ecx, dword ptr [rsp - 80] add ecx, dword ptr [rsp - 84] mov edx, dword ptr [rsp - 76] add edx, ecx mov ecx, dword ptr [rsp - 44] add ecx, edx add ecx, eax mov edx, dword ptr [rsp - 64] add edx, dword ptr [rsp - 68] mov eax, dword ptr [rsp - 60] add eax, edx mov edx, dword ptr [rsp - 56] add edx, eax mov eax, dword ptr [rsp - 48] add eax, edx add eax, ecx add rsp, 240 .cfi_def_cfa_offset 56 pop rbx .cfi_def_cfa_offset 48 pop r12 .cfi_def_cfa_offset 40 pop r13 .cfi_def_cfa_offset 32 pop r14 .cfi_def_cfa_offset 24 pop r15 .cfi_def_cfa_offset 16 pop rbp .cfi_def_cfa_offset 8 ret ``` </details> to ```assembly simd_sum_slow: .cfi_startproc xor eax, eax cmp rsi, 16 jb .LBB12_4 shl rsi, 2 pxor xmm0, xmm0 pxor xmm1, xmm1 pxor xmm3, xmm3 pxor xmm2, xmm2 .p2align 4 .LBB12_2: movdqu xmm4, xmmword ptr [rdi] paddd xmm0, xmm4 movdqu xmm4, xmmword ptr [rdi + 16] paddd xmm1, xmm4 movdqu xmm4, xmmword ptr [rdi + 32] paddd xmm3, xmm4 movdqu xmm4, xmmword ptr [rdi + 48] paddd xmm2, xmm4 add rdi, 64 add rsi, -64 cmp rsi, 60 ja .LBB12_2 paddd xmm0, xmm3 paddd xmm1, xmm2 paddd xmm1, xmm0 pshufd xmm0, xmm1, 238 paddd xmm0, xmm1 pshufd xmm1, xmm0, 85 paddd xmm1, xmm0 movd eax, xmm1 .LBB12_4: ret ```
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…unk, r=Mark-Simulacrum optimize `slice::Iter::next_chunk` codegen for example (sourced from rust-lang#98326 (comment)) ```rust pub fn simd_sum_slow(arr: &[u32]) -> u32 { const STEP_SIZE: usize = 16; let mut result = [0; STEP_SIZE]; let mut iter = arr.iter(); while let Ok(c) = iter.next_chunk::<STEP_SIZE>() { for (&n, r) in c.iter().zip(result.iter_mut()) { *r += n; } } result.iter().sum() } ``` goes from (znver4) <details> <summary>many asm</summary> ```assembly simd_sum_slow: .cfi_startproc push rbp .cfi_def_cfa_offset 16 push r15 .cfi_def_cfa_offset 24 push r14 .cfi_def_cfa_offset 32 push r13 .cfi_def_cfa_offset 40 push r12 .cfi_def_cfa_offset 48 push rbx .cfi_def_cfa_offset 56 sub rsp, 240 .cfi_def_cfa_offset 296 .cfi_offset rbx, -56 .cfi_offset r12, -48 .cfi_offset r13, -40 .cfi_offset r14, -32 .cfi_offset r15, -24 .cfi_offset rbp, -16 lea r12, [rdi + 4*rsi] mov qword ptr [rsp - 32], 0 mov dword ptr [rsp - 88], 0 mov dword ptr [rsp - 100], 0 mov dword ptr [rsp - 72], 0 mov dword ptr [rsp - 96], 0 mov dword ptr [rsp - 92], 0 mov dword ptr [rsp - 52], 0 mov dword ptr [rsp - 84], 0 mov dword ptr [rsp - 80], 0 mov dword ptr [rsp - 76], 0 mov dword ptr [rsp - 44], 0 mov dword ptr [rsp - 68], 0 mov dword ptr [rsp - 64], 0 mov dword ptr [rsp - 60], 0 mov dword ptr [rsp - 56], 0 mov dword ptr [rsp - 48], 0 mov qword ptr [rsp + 224], r12 cmp rdi, r12 mov qword ptr [rsp + 96], rdi je .LBB12_2 .p2align 4 .LBB12_3: lea r13, [rdi + 4] cmp r13, r12 je .LBB12_4 lea r15, [rdi + 8] cmp r15, r12 je .LBB12_6 lea r14, [rdi + 12] cmp r14, r12 je .LBB12_8 lea rbx, [rdi + 16] cmp rbx, r12 je .LBB12_10 lea r11, [rdi + 20] cmp r11, r12 je .LBB12_12 lea r10, [rdi + 24] cmp r10, r12 je .LBB12_14 lea r9, [rdi + 28] cmp r9, r12 je .LBB12_16 lea r8, [rdi + 32] cmp r8, r12 je .LBB12_18 lea rax, [rdi + 36] cmp rax, r12 je .LBB12_20 mov qword ptr [rsp - 120], rax lea rax, [rdi + 40] mov qword ptr [rsp - 112], rax cmp rax, r12 je .LBB12_22 lea rdx, [rdi + 44] cmp rdx, r12 je .LBB12_24 lea rbp, [rdi + 48] cmp rbp, r12 je .LBB12_26 mov qword ptr [rsp - 40], r9 lea rcx, [rdi + 52] cmp rcx, r12 je .LBB12_30 lea r9, [rdi + 56] cmp r9, r12 je .LBB12_32 lea rax, [rdi + 60] cmp rax, r12 mov qword ptr [rsp - 24], r9 je .LBB12_34 mov qword ptr [rsp + 88], rax lea rax, [rdi + 64] mov qword ptr [rsp - 8], rax mov dword ptr [rsp - 128], 0 mov qword ptr [rsp - 16], rdi mov qword ptr [rsp + 56], r10 lea r10, [rsp + 216] mov qword ptr [rsp + 40], r10 mov qword ptr [rsp + 96], r13 lea rax, [rsp + 208] mov qword ptr [rsp + 32], rax mov qword ptr [rsp + 72], rdx lea rsi, [rsp + 200] mov qword ptr [rsp + 48], rbx lea rbx, [rsp + 192] mov qword ptr [rsp + 80], rcx lea rcx, [rsp + 184] mov qword ptr [rsp + 64], rbp lea rdx, [rsp + 176] mov qword ptr [rsp + 16], r14 lea r14, [rsp + 168] mov qword ptr [rsp + 24], r11 lea r11, [rsp + 160] lea r9, [rsp + 152] lea r12, [rsp + 144] lea r13, [rsp + 136] lea rbp, [rsp + 128] mov qword ptr [rsp], r15 lea r15, [rsp + 120] mov qword ptr [rsp + 8], r8 lea r8, [rsp + 112] lea rdi, [rsp + 104] jmp .LBB12_39 .p2align 4 .LBB12_2: mov qword ptr [rsp - 128], 0 jmp .LBB12_37 .p2align 4 .LBB12_4: mov eax, 1 mov qword ptr [rsp - 128], rax jmp .LBB12_37 .p2align 4 .LBB12_6: mov eax, 2 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_8: mov eax, 3 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_10: mov eax, 4 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_12: mov eax, 5 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_14: mov eax, 6 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_16: mov eax, 7 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_18: mov eax, 8 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_20: mov eax, 9 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_22: mov eax, 10 mov qword ptr [rsp - 128], rax mov rdi, qword ptr [rsp - 120] jmp .LBB12_36 .LBB12_24: mov eax, 11 mov qword ptr [rsp - 128], rax jmp .LBB12_27 .LBB12_26: mov eax, 12 mov qword ptr [rsp - 128], rax .LBB12_27: mov rsi, qword ptr [rsp - 112] mov rdi, qword ptr [rsp - 120] jmp .LBB12_36 .LBB12_30: mov rcx, rbp mov eax, 13 mov qword ptr [rsp - 128], rax jmp .LBB12_35 .LBB12_32: mov rax, rcx mov rcx, rbp mov esi, 14 mov qword ptr [rsp - 128], rsi jmp .LBB12_35 .LBB12_34: mov rax, rcx mov rcx, rbp mov esi, 15 mov qword ptr [rsp - 128], rsi .LBB12_35: mov rsi, qword ptr [rsp - 112] mov rdi, qword ptr [rsp - 120] mov r9, qword ptr [rsp - 40] .p2align 4 .LBB12_36: mov rbp, r13 .LBB12_37: mov r13, qword ptr [rsp - 24] mov qword ptr [rsp + 88], r13 mov r13, qword ptr [rsp - 128] mov qword ptr [rsp + 216], r13 mov r13b, 1 mov dword ptr [rsp - 128], r13d mov qword ptr [rsp - 24], rax mov qword ptr [rsp + 80], rcx mov qword ptr [rsp + 64], rdx mov qword ptr [rsp + 72], rsi mov qword ptr [rsp - 112], rdi mov qword ptr [rsp - 120], r8 mov qword ptr [rsp + 8], r9 mov qword ptr [rsp - 40], r10 mov qword ptr [rsp + 56], r11 mov qword ptr [rsp + 24], rbx mov qword ptr [rsp + 48], r14 mov qword ptr [rsp + 16], r15 mov qword ptr [rsp], rbp mov eax, 0 mov qword ptr [rsp - 16], rax mov qword ptr [rsp - 8], r12 lea r10, [rsp + 208] mov qword ptr [rsp + 40], r10 lea rax, [rsp + 200] mov qword ptr [rsp + 32], rax lea rsi, [rsp + 192] lea rbx, [rsp + 184] lea rcx, [rsp + 176] lea rdx, [rsp + 168] lea r14, [rsp + 160] lea r11, [rsp + 152] lea r9, [rsp + 144] lea r12, [rsp + 136] lea r13, [rsp + 128] lea rbp, [rsp + 120] lea r15, [rsp + 112] lea r8, [rsp + 104] lea rdi, [rsp + 232] .LBB12_39: mov r10, qword ptr [rsp + 96] mov rax, qword ptr [rsp + 40] mov qword ptr [rax], r10 mov rax, qword ptr [rsp + 32] mov r10, qword ptr [rsp] mov qword ptr [rax], r10 mov rax, qword ptr [rsp + 16] mov qword ptr [rsi], rax mov rax, qword ptr [rsp + 48] mov qword ptr [rbx], rax mov rax, qword ptr [rsp + 24] mov qword ptr [rcx], rax mov rax, qword ptr [rsp + 56] mov qword ptr [rdx], rax mov rax, qword ptr [rsp - 40] mov qword ptr [r14], rax mov rax, qword ptr [rsp + 8] mov qword ptr [r11], rax mov rax, qword ptr [rsp - 120] mov qword ptr [r9], rax mov rax, qword ptr [rsp - 112] mov qword ptr [r12], rax mov rax, qword ptr [rsp + 72] mov qword ptr [r13], rax mov rax, qword ptr [rsp + 64] mov qword ptr [rbp], rax mov rax, qword ptr [rsp + 80] mov qword ptr [r15], rax mov rax, qword ptr [rsp - 24] mov qword ptr [r8], rax mov rax, qword ptr [rsp + 88] mov qword ptr [rdi], rax cmp byte ptr [rsp - 128], 0 jne .LBB12_40 mov rax, qword ptr [rsp - 32] mov rcx, qword ptr [rsp - 16] add eax, dword ptr [rcx] mov qword ptr [rsp - 32], rax mov rax, qword ptr [rsp + 216] mov ecx, dword ptr [rsp - 88] add ecx, dword ptr [rax] mov dword ptr [rsp - 88], ecx mov rax, qword ptr [rsp + 208] mov ecx, dword ptr [rsp - 100] add ecx, dword ptr [rax] mov dword ptr [rsp - 100], ecx mov rax, qword ptr [rsp + 200] mov ecx, dword ptr [rsp - 72] add ecx, dword ptr [rax] mov dword ptr [rsp - 72], ecx mov rax, qword ptr [rsp + 192] mov ecx, dword ptr [rsp - 96] add ecx, dword ptr [rax] mov dword ptr [rsp - 96], ecx mov rax, qword ptr [rsp + 184] mov ecx, dword ptr [rsp - 92] add ecx, dword ptr [rax] mov dword ptr [rsp - 92], ecx mov rax, qword ptr [rsp + 176] mov ecx, dword ptr [rsp - 52] add ecx, dword ptr [rax] mov dword ptr [rsp - 52], ecx mov rax, qword ptr [rsp + 168] mov ecx, dword ptr [rsp - 84] add ecx, dword ptr [rax] mov dword ptr [rsp - 84], ecx mov rax, qword ptr [rsp + 160] mov ecx, dword ptr [rsp - 80] add ecx, dword ptr [rax] mov dword ptr [rsp - 80], ecx mov rax, qword ptr [rsp + 152] mov ecx, dword ptr [rsp - 76] add ecx, dword ptr [rax] mov dword ptr [rsp - 76], ecx mov rax, qword ptr [rsp + 144] mov ecx, dword ptr [rsp - 44] add ecx, dword ptr [rax] mov dword ptr [rsp - 44], ecx mov rax, qword ptr [rsp + 136] mov ecx, dword ptr [rsp - 68] add ecx, dword ptr [rax] mov dword ptr [rsp - 68], ecx mov rax, qword ptr [rsp + 128] mov ecx, dword ptr [rsp - 64] add ecx, dword ptr [rax] mov dword ptr [rsp - 64], ecx mov rax, qword ptr [rsp + 120] mov ecx, dword ptr [rsp - 60] add ecx, dword ptr [rax] mov dword ptr [rsp - 60], ecx mov rax, qword ptr [rsp + 112] mov ecx, dword ptr [rsp - 56] add ecx, dword ptr [rax] mov dword ptr [rsp - 56], ecx mov rax, qword ptr [rsp + 104] mov ecx, dword ptr [rsp - 48] add ecx, dword ptr [rax] mov dword ptr [rsp - 48], ecx mov rdi, qword ptr [rsp - 8] mov r12, qword ptr [rsp + 224] cmp rdi, r12 mov qword ptr [rsp + 96], rdi jne .LBB12_3 jmp .LBB12_2 .LBB12_40: mov eax, dword ptr [rsp - 88] add eax, dword ptr [rsp - 32] mov ecx, dword ptr [rsp - 72] add ecx, dword ptr [rsp - 100] add ecx, eax mov edx, dword ptr [rsp - 92] add edx, dword ptr [rsp - 96] mov eax, dword ptr [rsp - 52] add eax, edx add eax, ecx mov ecx, dword ptr [rsp - 80] add ecx, dword ptr [rsp - 84] mov edx, dword ptr [rsp - 76] add edx, ecx mov ecx, dword ptr [rsp - 44] add ecx, edx add ecx, eax mov edx, dword ptr [rsp - 64] add edx, dword ptr [rsp - 68] mov eax, dword ptr [rsp - 60] add eax, edx mov edx, dword ptr [rsp - 56] add edx, eax mov eax, dword ptr [rsp - 48] add eax, edx add eax, ecx add rsp, 240 .cfi_def_cfa_offset 56 pop rbx .cfi_def_cfa_offset 48 pop r12 .cfi_def_cfa_offset 40 pop r13 .cfi_def_cfa_offset 32 pop r14 .cfi_def_cfa_offset 24 pop r15 .cfi_def_cfa_offset 16 pop rbp .cfi_def_cfa_offset 8 ret ``` </details> to ```assembly simd_sum_slow: .cfi_startproc xor eax, eax cmp rsi, 16 jb .LBB12_4 shl rsi, 2 pxor xmm0, xmm0 pxor xmm1, xmm1 pxor xmm3, xmm3 pxor xmm2, xmm2 .p2align 4 .LBB12_2: movdqu xmm4, xmmword ptr [rdi] paddd xmm0, xmm4 movdqu xmm4, xmmword ptr [rdi + 16] paddd xmm1, xmm4 movdqu xmm4, xmmword ptr [rdi + 32] paddd xmm3, xmm4 movdqu xmm4, xmmword ptr [rdi + 48] paddd xmm2, xmm4 add rdi, 64 add rsi, -64 cmp rsi, 60 ja .LBB12_2 paddd xmm0, xmm3 paddd xmm1, xmm2 paddd xmm1, xmm0 pshufd xmm0, xmm1, 238 paddd xmm0, xmm1 pshufd xmm1, xmm0, 85 paddd xmm1, xmm0 movd eax, xmm1 .LBB12_4: ret ```
Zalathar added a commit
to Zalathar/rust
that referenced
this pull request
Nov 26, 2025
…unk, r=Mark-Simulacrum optimize `slice::Iter::next_chunk` codegen for example (sourced from rust-lang#98326 (comment)) ```rust pub fn simd_sum_slow(arr: &[u32]) -> u32 { const STEP_SIZE: usize = 16; let mut result = [0; STEP_SIZE]; let mut iter = arr.iter(); while let Ok(c) = iter.next_chunk::<STEP_SIZE>() { for (&n, r) in c.iter().zip(result.iter_mut()) { *r += n; } } result.iter().sum() } ``` goes from (znver4) <details> <summary>many asm</summary> ```assembly simd_sum_slow: .cfi_startproc push rbp .cfi_def_cfa_offset 16 push r15 .cfi_def_cfa_offset 24 push r14 .cfi_def_cfa_offset 32 push r13 .cfi_def_cfa_offset 40 push r12 .cfi_def_cfa_offset 48 push rbx .cfi_def_cfa_offset 56 sub rsp, 240 .cfi_def_cfa_offset 296 .cfi_offset rbx, -56 .cfi_offset r12, -48 .cfi_offset r13, -40 .cfi_offset r14, -32 .cfi_offset r15, -24 .cfi_offset rbp, -16 lea r12, [rdi + 4*rsi] mov qword ptr [rsp - 32], 0 mov dword ptr [rsp - 88], 0 mov dword ptr [rsp - 100], 0 mov dword ptr [rsp - 72], 0 mov dword ptr [rsp - 96], 0 mov dword ptr [rsp - 92], 0 mov dword ptr [rsp - 52], 0 mov dword ptr [rsp - 84], 0 mov dword ptr [rsp - 80], 0 mov dword ptr [rsp - 76], 0 mov dword ptr [rsp - 44], 0 mov dword ptr [rsp - 68], 0 mov dword ptr [rsp - 64], 0 mov dword ptr [rsp - 60], 0 mov dword ptr [rsp - 56], 0 mov dword ptr [rsp - 48], 0 mov qword ptr [rsp + 224], r12 cmp rdi, r12 mov qword ptr [rsp + 96], rdi je .LBB12_2 .p2align 4 .LBB12_3: lea r13, [rdi + 4] cmp r13, r12 je .LBB12_4 lea r15, [rdi + 8] cmp r15, r12 je .LBB12_6 lea r14, [rdi + 12] cmp r14, r12 je .LBB12_8 lea rbx, [rdi + 16] cmp rbx, r12 je .LBB12_10 lea r11, [rdi + 20] cmp r11, r12 je .LBB12_12 lea r10, [rdi + 24] cmp r10, r12 je .LBB12_14 lea r9, [rdi + 28] cmp r9, r12 je .LBB12_16 lea r8, [rdi + 32] cmp r8, r12 je .LBB12_18 lea rax, [rdi + 36] cmp rax, r12 je .LBB12_20 mov qword ptr [rsp - 120], rax lea rax, [rdi + 40] mov qword ptr [rsp - 112], rax cmp rax, r12 je .LBB12_22 lea rdx, [rdi + 44] cmp rdx, r12 je .LBB12_24 lea rbp, [rdi + 48] cmp rbp, r12 je .LBB12_26 mov qword ptr [rsp - 40], r9 lea rcx, [rdi + 52] cmp rcx, r12 je .LBB12_30 lea r9, [rdi + 56] cmp r9, r12 je .LBB12_32 lea rax, [rdi + 60] cmp rax, r12 mov qword ptr [rsp - 24], r9 je .LBB12_34 mov qword ptr [rsp + 88], rax lea rax, [rdi + 64] mov qword ptr [rsp - 8], rax mov dword ptr [rsp - 128], 0 mov qword ptr [rsp - 16], rdi mov qword ptr [rsp + 56], r10 lea r10, [rsp + 216] mov qword ptr [rsp + 40], r10 mov qword ptr [rsp + 96], r13 lea rax, [rsp + 208] mov qword ptr [rsp + 32], rax mov qword ptr [rsp + 72], rdx lea rsi, [rsp + 200] mov qword ptr [rsp + 48], rbx lea rbx, [rsp + 192] mov qword ptr [rsp + 80], rcx lea rcx, [rsp + 184] mov qword ptr [rsp + 64], rbp lea rdx, [rsp + 176] mov qword ptr [rsp + 16], r14 lea r14, [rsp + 168] mov qword ptr [rsp + 24], r11 lea r11, [rsp + 160] lea r9, [rsp + 152] lea r12, [rsp + 144] lea r13, [rsp + 136] lea rbp, [rsp + 128] mov qword ptr [rsp], r15 lea r15, [rsp + 120] mov qword ptr [rsp + 8], r8 lea r8, [rsp + 112] lea rdi, [rsp + 104] jmp .LBB12_39 .p2align 4 .LBB12_2: mov qword ptr [rsp - 128], 0 jmp .LBB12_37 .p2align 4 .LBB12_4: mov eax, 1 mov qword ptr [rsp - 128], rax jmp .LBB12_37 .p2align 4 .LBB12_6: mov eax, 2 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_8: mov eax, 3 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_10: mov eax, 4 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_12: mov eax, 5 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_14: mov eax, 6 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_16: mov eax, 7 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_18: mov eax, 8 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_20: mov eax, 9 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_22: mov eax, 10 mov qword ptr [rsp - 128], rax mov rdi, qword ptr [rsp - 120] jmp .LBB12_36 .LBB12_24: mov eax, 11 mov qword ptr [rsp - 128], rax jmp .LBB12_27 .LBB12_26: mov eax, 12 mov qword ptr [rsp - 128], rax .LBB12_27: mov rsi, qword ptr [rsp - 112] mov rdi, qword ptr [rsp - 120] jmp .LBB12_36 .LBB12_30: mov rcx, rbp mov eax, 13 mov qword ptr [rsp - 128], rax jmp .LBB12_35 .LBB12_32: mov rax, rcx mov rcx, rbp mov esi, 14 mov qword ptr [rsp - 128], rsi jmp .LBB12_35 .LBB12_34: mov rax, rcx mov rcx, rbp mov esi, 15 mov qword ptr [rsp - 128], rsi .LBB12_35: mov rsi, qword ptr [rsp - 112] mov rdi, qword ptr [rsp - 120] mov r9, qword ptr [rsp - 40] .p2align 4 .LBB12_36: mov rbp, r13 .LBB12_37: mov r13, qword ptr [rsp - 24] mov qword ptr [rsp + 88], r13 mov r13, qword ptr [rsp - 128] mov qword ptr [rsp + 216], r13 mov r13b, 1 mov dword ptr [rsp - 128], r13d mov qword ptr [rsp - 24], rax mov qword ptr [rsp + 80], rcx mov qword ptr [rsp + 64], rdx mov qword ptr [rsp + 72], rsi mov qword ptr [rsp - 112], rdi mov qword ptr [rsp - 120], r8 mov qword ptr [rsp + 8], r9 mov qword ptr [rsp - 40], r10 mov qword ptr [rsp + 56], r11 mov qword ptr [rsp + 24], rbx mov qword ptr [rsp + 48], r14 mov qword ptr [rsp + 16], r15 mov qword ptr [rsp], rbp mov eax, 0 mov qword ptr [rsp - 16], rax mov qword ptr [rsp - 8], r12 lea r10, [rsp + 208] mov qword ptr [rsp + 40], r10 lea rax, [rsp + 200] mov qword ptr [rsp + 32], rax lea rsi, [rsp + 192] lea rbx, [rsp + 184] lea rcx, [rsp + 176] lea rdx, [rsp + 168] lea r14, [rsp + 160] lea r11, [rsp + 152] lea r9, [rsp + 144] lea r12, [rsp + 136] lea r13, [rsp + 128] lea rbp, [rsp + 120] lea r15, [rsp + 112] lea r8, [rsp + 104] lea rdi, [rsp + 232] .LBB12_39: mov r10, qword ptr [rsp + 96] mov rax, qword ptr [rsp + 40] mov qword ptr [rax], r10 mov rax, qword ptr [rsp + 32] mov r10, qword ptr [rsp] mov qword ptr [rax], r10 mov rax, qword ptr [rsp + 16] mov qword ptr [rsi], rax mov rax, qword ptr [rsp + 48] mov qword ptr [rbx], rax mov rax, qword ptr [rsp + 24] mov qword ptr [rcx], rax mov rax, qword ptr [rsp + 56] mov qword ptr [rdx], rax mov rax, qword ptr [rsp - 40] mov qword ptr [r14], rax mov rax, qword ptr [rsp + 8] mov qword ptr [r11], rax mov rax, qword ptr [rsp - 120] mov qword ptr [r9], rax mov rax, qword ptr [rsp - 112] mov qword ptr [r12], rax mov rax, qword ptr [rsp + 72] mov qword ptr [r13], rax mov rax, qword ptr [rsp + 64] mov qword ptr [rbp], rax mov rax, qword ptr [rsp + 80] mov qword ptr [r15], rax mov rax, qword ptr [rsp - 24] mov qword ptr [r8], rax mov rax, qword ptr [rsp + 88] mov qword ptr [rdi], rax cmp byte ptr [rsp - 128], 0 jne .LBB12_40 mov rax, qword ptr [rsp - 32] mov rcx, qword ptr [rsp - 16] add eax, dword ptr [rcx] mov qword ptr [rsp - 32], rax mov rax, qword ptr [rsp + 216] mov ecx, dword ptr [rsp - 88] add ecx, dword ptr [rax] mov dword ptr [rsp - 88], ecx mov rax, qword ptr [rsp + 208] mov ecx, dword ptr [rsp - 100] add ecx, dword ptr [rax] mov dword ptr [rsp - 100], ecx mov rax, qword ptr [rsp + 200] mov ecx, dword ptr [rsp - 72] add ecx, dword ptr [rax] mov dword ptr [rsp - 72], ecx mov rax, qword ptr [rsp + 192] mov ecx, dword ptr [rsp - 96] add ecx, dword ptr [rax] mov dword ptr [rsp - 96], ecx mov rax, qword ptr [rsp + 184] mov ecx, dword ptr [rsp - 92] add ecx, dword ptr [rax] mov dword ptr [rsp - 92], ecx mov rax, qword ptr [rsp + 176] mov ecx, dword ptr [rsp - 52] add ecx, dword ptr [rax] mov dword ptr [rsp - 52], ecx mov rax, qword ptr [rsp + 168] mov ecx, dword ptr [rsp - 84] add ecx, dword ptr [rax] mov dword ptr [rsp - 84], ecx mov rax, qword ptr [rsp + 160] mov ecx, dword ptr [rsp - 80] add ecx, dword ptr [rax] mov dword ptr [rsp - 80], ecx mov rax, qword ptr [rsp + 152] mov ecx, dword ptr [rsp - 76] add ecx, dword ptr [rax] mov dword ptr [rsp - 76], ecx mov rax, qword ptr [rsp + 144] mov ecx, dword ptr [rsp - 44] add ecx, dword ptr [rax] mov dword ptr [rsp - 44], ecx mov rax, qword ptr [rsp + 136] mov ecx, dword ptr [rsp - 68] add ecx, dword ptr [rax] mov dword ptr [rsp - 68], ecx mov rax, qword ptr [rsp + 128] mov ecx, dword ptr [rsp - 64] add ecx, dword ptr [rax] mov dword ptr [rsp - 64], ecx mov rax, qword ptr [rsp + 120] mov ecx, dword ptr [rsp - 60] add ecx, dword ptr [rax] mov dword ptr [rsp - 60], ecx mov rax, qword ptr [rsp + 112] mov ecx, dword ptr [rsp - 56] add ecx, dword ptr [rax] mov dword ptr [rsp - 56], ecx mov rax, qword ptr [rsp + 104] mov ecx, dword ptr [rsp - 48] add ecx, dword ptr [rax] mov dword ptr [rsp - 48], ecx mov rdi, qword ptr [rsp - 8] mov r12, qword ptr [rsp + 224] cmp rdi, r12 mov qword ptr [rsp + 96], rdi jne .LBB12_3 jmp .LBB12_2 .LBB12_40: mov eax, dword ptr [rsp - 88] add eax, dword ptr [rsp - 32] mov ecx, dword ptr [rsp - 72] add ecx, dword ptr [rsp - 100] add ecx, eax mov edx, dword ptr [rsp - 92] add edx, dword ptr [rsp - 96] mov eax, dword ptr [rsp - 52] add eax, edx add eax, ecx mov ecx, dword ptr [rsp - 80] add ecx, dword ptr [rsp - 84] mov edx, dword ptr [rsp - 76] add edx, ecx mov ecx, dword ptr [rsp - 44] add ecx, edx add ecx, eax mov edx, dword ptr [rsp - 64] add edx, dword ptr [rsp - 68] mov eax, dword ptr [rsp - 60] add eax, edx mov edx, dword ptr [rsp - 56] add edx, eax mov eax, dword ptr [rsp - 48] add eax, edx add eax, ecx add rsp, 240 .cfi_def_cfa_offset 56 pop rbx .cfi_def_cfa_offset 48 pop r12 .cfi_def_cfa_offset 40 pop r13 .cfi_def_cfa_offset 32 pop r14 .cfi_def_cfa_offset 24 pop r15 .cfi_def_cfa_offset 16 pop rbp .cfi_def_cfa_offset 8 ret ``` </details> to ```assembly simd_sum_slow: .cfi_startproc xor eax, eax cmp rsi, 16 jb .LBB12_4 shl rsi, 2 pxor xmm0, xmm0 pxor xmm1, xmm1 pxor xmm3, xmm3 pxor xmm2, xmm2 .p2align 4 .LBB12_2: movdqu xmm4, xmmword ptr [rdi] paddd xmm0, xmm4 movdqu xmm4, xmmword ptr [rdi + 16] paddd xmm1, xmm4 movdqu xmm4, xmmword ptr [rdi + 32] paddd xmm3, xmm4 movdqu xmm4, xmmword ptr [rdi + 48] paddd xmm2, xmm4 add rdi, 64 add rsi, -64 cmp rsi, 60 ja .LBB12_2 paddd xmm0, xmm3 paddd xmm1, xmm2 paddd xmm1, xmm0 pshufd xmm0, xmm1, 238 paddd xmm0, xmm1 pshufd xmm1, xmm0, 85 paddd xmm1, xmm0 movd eax, xmm1 .LBB12_4: ret ```
bors added a commit
that referenced
this pull request
Nov 26, 2025
Rollup of 19 pull requests Successful merges: - #148048 (Stabilize `maybe_uninit_write_slice`) - #148641 (Add a diagnostic attribute for special casing const bound errors for non-const impls) - #148765 (std: split up the `thread` module) - #149074 (Add Command::get_env_clear) - #149097 (num: Implement `uint_gather_scatter_bits` feature for unsigned integers) - #149131 (optimize `slice::Iter::next_chunk`) - #149190 (Forbid `CHECK: br` and `CHECK-NOT: br` in codegen tests (suggest `br {{.*}}` instead)) - #149239 (clarify float min/max behavios for NaNs and signed zeros) - #149243 (Fix typo and clarify bootstrap change tracker entry) - #149270 (implement `Iterator::{exactly_one, collect_array}`) - #149295 (Suggest _bytes versions of endian-converting methods) - #149301 (Motor OS: make decode_error_kind more comprehensive) - #149306 (bootstrap: Miri now handles jemalloc like everything else) - #149325 (rustdoc: add regression test for #140968) - #149332 (fix rustdoc search says “Consider searching for "null" instead.” #149324) - #149349 (Fix typo in comment.) - #149353 (Tidying up UI tests [3/N]) - #149355 (Document that `build.description` affects symbol mangling and crate IDs) - #149360 (Enable CI download for windows-gnullvm) r? `@ghost` `@rustbot` modify labels: rollup
bors added a commit
that referenced
this pull request
Nov 27, 2025
Rollup of 12 pull requests Successful merges: - #147115 (More robust stack protector testing) - #148048 (Stabilize `maybe_uninit_write_slice`) - #148641 (Add a diagnostic attribute for special casing const bound errors for non-const impls) - #149074 (Add Command::get_env_clear) - #149097 (num: Implement `uint_gather_scatter_bits` feature for unsigned integers) - #149131 (optimize `slice::Iter::next_chunk`) - #149190 (Forbid `CHECK: br` and `CHECK-NOT: br` in codegen tests (suggest `br {{.*}}` instead)) - #149239 (clarify float min/max behavios for NaNs and signed zeros) - #149243 (Fix typo and clarify bootstrap change tracker entry) - #149301 (Motor OS: make decode_error_kind more comprehensive) - #149306 (bootstrap: Miri now handles jemalloc like everything else) - #149325 (rustdoc: add regression test for #140968) r? `@ghost` `@rustbot` modify labels: rollup
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rust-timer added a commit
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Nov 27, 2025
Rollup merge of #149131 - bend-n:optimize_slice_iter_next_chunk, r=Mark-Simulacrum optimize `slice::Iter::next_chunk` codegen for example (sourced from #98326 (comment)) ```rust pub fn simd_sum_slow(arr: &[u32]) -> u32 { const STEP_SIZE: usize = 16; let mut result = [0; STEP_SIZE]; let mut iter = arr.iter(); while let Ok(c) = iter.next_chunk::<STEP_SIZE>() { for (&n, r) in c.iter().zip(result.iter_mut()) { *r += n; } } result.iter().sum() } ``` goes from (znver4) <details> <summary>many asm</summary> ```assembly simd_sum_slow: .cfi_startproc push rbp .cfi_def_cfa_offset 16 push r15 .cfi_def_cfa_offset 24 push r14 .cfi_def_cfa_offset 32 push r13 .cfi_def_cfa_offset 40 push r12 .cfi_def_cfa_offset 48 push rbx .cfi_def_cfa_offset 56 sub rsp, 240 .cfi_def_cfa_offset 296 .cfi_offset rbx, -56 .cfi_offset r12, -48 .cfi_offset r13, -40 .cfi_offset r14, -32 .cfi_offset r15, -24 .cfi_offset rbp, -16 lea r12, [rdi + 4*rsi] mov qword ptr [rsp - 32], 0 mov dword ptr [rsp - 88], 0 mov dword ptr [rsp - 100], 0 mov dword ptr [rsp - 72], 0 mov dword ptr [rsp - 96], 0 mov dword ptr [rsp - 92], 0 mov dword ptr [rsp - 52], 0 mov dword ptr [rsp - 84], 0 mov dword ptr [rsp - 80], 0 mov dword ptr [rsp - 76], 0 mov dword ptr [rsp - 44], 0 mov dword ptr [rsp - 68], 0 mov dword ptr [rsp - 64], 0 mov dword ptr [rsp - 60], 0 mov dword ptr [rsp - 56], 0 mov dword ptr [rsp - 48], 0 mov qword ptr [rsp + 224], r12 cmp rdi, r12 mov qword ptr [rsp + 96], rdi je .LBB12_2 .p2align 4 .LBB12_3: lea r13, [rdi + 4] cmp r13, r12 je .LBB12_4 lea r15, [rdi + 8] cmp r15, r12 je .LBB12_6 lea r14, [rdi + 12] cmp r14, r12 je .LBB12_8 lea rbx, [rdi + 16] cmp rbx, r12 je .LBB12_10 lea r11, [rdi + 20] cmp r11, r12 je .LBB12_12 lea r10, [rdi + 24] cmp r10, r12 je .LBB12_14 lea r9, [rdi + 28] cmp r9, r12 je .LBB12_16 lea r8, [rdi + 32] cmp r8, r12 je .LBB12_18 lea rax, [rdi + 36] cmp rax, r12 je .LBB12_20 mov qword ptr [rsp - 120], rax lea rax, [rdi + 40] mov qword ptr [rsp - 112], rax cmp rax, r12 je .LBB12_22 lea rdx, [rdi + 44] cmp rdx, r12 je .LBB12_24 lea rbp, [rdi + 48] cmp rbp, r12 je .LBB12_26 mov qword ptr [rsp - 40], r9 lea rcx, [rdi + 52] cmp rcx, r12 je .LBB12_30 lea r9, [rdi + 56] cmp r9, r12 je .LBB12_32 lea rax, [rdi + 60] cmp rax, r12 mov qword ptr [rsp - 24], r9 je .LBB12_34 mov qword ptr [rsp + 88], rax lea rax, [rdi + 64] mov qword ptr [rsp - 8], rax mov dword ptr [rsp - 128], 0 mov qword ptr [rsp - 16], rdi mov qword ptr [rsp + 56], r10 lea r10, [rsp + 216] mov qword ptr [rsp + 40], r10 mov qword ptr [rsp + 96], r13 lea rax, [rsp + 208] mov qword ptr [rsp + 32], rax mov qword ptr [rsp + 72], rdx lea rsi, [rsp + 200] mov qword ptr [rsp + 48], rbx lea rbx, [rsp + 192] mov qword ptr [rsp + 80], rcx lea rcx, [rsp + 184] mov qword ptr [rsp + 64], rbp lea rdx, [rsp + 176] mov qword ptr [rsp + 16], r14 lea r14, [rsp + 168] mov qword ptr [rsp + 24], r11 lea r11, [rsp + 160] lea r9, [rsp + 152] lea r12, [rsp + 144] lea r13, [rsp + 136] lea rbp, [rsp + 128] mov qword ptr [rsp], r15 lea r15, [rsp + 120] mov qword ptr [rsp + 8], r8 lea r8, [rsp + 112] lea rdi, [rsp + 104] jmp .LBB12_39 .p2align 4 .LBB12_2: mov qword ptr [rsp - 128], 0 jmp .LBB12_37 .p2align 4 .LBB12_4: mov eax, 1 mov qword ptr [rsp - 128], rax jmp .LBB12_37 .p2align 4 .LBB12_6: mov eax, 2 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_8: mov eax, 3 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_10: mov eax, 4 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_12: mov eax, 5 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_14: mov eax, 6 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_16: mov eax, 7 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_18: mov eax, 8 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_20: mov eax, 9 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_22: mov eax, 10 mov qword ptr [rsp - 128], rax mov rdi, qword ptr [rsp - 120] jmp .LBB12_36 .LBB12_24: mov eax, 11 mov qword ptr [rsp - 128], rax jmp .LBB12_27 .LBB12_26: mov eax, 12 mov qword ptr [rsp - 128], rax .LBB12_27: mov rsi, qword ptr [rsp - 112] mov rdi, qword ptr [rsp - 120] jmp .LBB12_36 .LBB12_30: mov rcx, rbp mov eax, 13 mov qword ptr [rsp - 128], rax jmp .LBB12_35 .LBB12_32: mov rax, rcx mov rcx, rbp mov esi, 14 mov qword ptr [rsp - 128], rsi jmp .LBB12_35 .LBB12_34: mov rax, rcx mov rcx, rbp mov esi, 15 mov qword ptr [rsp - 128], rsi .LBB12_35: mov rsi, qword ptr [rsp - 112] mov rdi, qword ptr [rsp - 120] mov r9, qword ptr [rsp - 40] .p2align 4 .LBB12_36: mov rbp, r13 .LBB12_37: mov r13, qword ptr [rsp - 24] mov qword ptr [rsp + 88], r13 mov r13, qword ptr [rsp - 128] mov qword ptr [rsp + 216], r13 mov r13b, 1 mov dword ptr [rsp - 128], r13d mov qword ptr [rsp - 24], rax mov qword ptr [rsp + 80], rcx mov qword ptr [rsp + 64], rdx mov qword ptr [rsp + 72], rsi mov qword ptr [rsp - 112], rdi mov qword ptr [rsp - 120], r8 mov qword ptr [rsp + 8], r9 mov qword ptr [rsp - 40], r10 mov qword ptr [rsp + 56], r11 mov qword ptr [rsp + 24], rbx mov qword ptr [rsp + 48], r14 mov qword ptr [rsp + 16], r15 mov qword ptr [rsp], rbp mov eax, 0 mov qword ptr [rsp - 16], rax mov qword ptr [rsp - 8], r12 lea r10, [rsp + 208] mov qword ptr [rsp + 40], r10 lea rax, [rsp + 200] mov qword ptr [rsp + 32], rax lea rsi, [rsp + 192] lea rbx, [rsp + 184] lea rcx, [rsp + 176] lea rdx, [rsp + 168] lea r14, [rsp + 160] lea r11, [rsp + 152] lea r9, [rsp + 144] lea r12, [rsp + 136] lea r13, [rsp + 128] lea rbp, [rsp + 120] lea r15, [rsp + 112] lea r8, [rsp + 104] lea rdi, [rsp + 232] .LBB12_39: mov r10, qword ptr [rsp + 96] mov rax, qword ptr [rsp + 40] mov qword ptr [rax], r10 mov rax, qword ptr [rsp + 32] mov r10, qword ptr [rsp] mov qword ptr [rax], r10 mov rax, qword ptr [rsp + 16] mov qword ptr [rsi], rax mov rax, qword ptr [rsp + 48] mov qword ptr [rbx], rax mov rax, qword ptr [rsp + 24] mov qword ptr [rcx], rax mov rax, qword ptr [rsp + 56] mov qword ptr [rdx], rax mov rax, qword ptr [rsp - 40] mov qword ptr [r14], rax mov rax, qword ptr [rsp + 8] mov qword ptr [r11], rax mov rax, qword ptr [rsp - 120] mov qword ptr [r9], rax mov rax, qword ptr [rsp - 112] mov qword ptr [r12], rax mov rax, qword ptr [rsp + 72] mov qword ptr [r13], rax mov rax, qword ptr [rsp + 64] mov qword ptr [rbp], rax mov rax, qword ptr [rsp + 80] mov qword ptr [r15], rax mov rax, qword ptr [rsp - 24] mov qword ptr [r8], rax mov rax, qword ptr [rsp + 88] mov qword ptr [rdi], rax cmp byte ptr [rsp - 128], 0 jne .LBB12_40 mov rax, qword ptr [rsp - 32] mov rcx, qword ptr [rsp - 16] add eax, dword ptr [rcx] mov qword ptr [rsp - 32], rax mov rax, qword ptr [rsp + 216] mov ecx, dword ptr [rsp - 88] add ecx, dword ptr [rax] mov dword ptr [rsp - 88], ecx mov rax, qword ptr [rsp + 208] mov ecx, dword ptr [rsp - 100] add ecx, dword ptr [rax] mov dword ptr [rsp - 100], ecx mov rax, qword ptr [rsp + 200] mov ecx, dword ptr [rsp - 72] add ecx, dword ptr [rax] mov dword ptr [rsp - 72], ecx mov rax, qword ptr [rsp + 192] mov ecx, dword ptr [rsp - 96] add ecx, dword ptr [rax] mov dword ptr [rsp - 96], ecx mov rax, qword ptr [rsp + 184] mov ecx, dword ptr [rsp - 92] add ecx, dword ptr [rax] mov dword ptr [rsp - 92], ecx mov rax, qword ptr [rsp + 176] mov ecx, dword ptr [rsp - 52] add ecx, dword ptr [rax] mov dword ptr [rsp - 52], ecx mov rax, qword ptr [rsp + 168] mov ecx, dword ptr [rsp - 84] add ecx, dword ptr [rax] mov dword ptr [rsp - 84], ecx mov rax, qword ptr [rsp + 160] mov ecx, dword ptr [rsp - 80] add ecx, dword ptr [rax] mov dword ptr [rsp - 80], ecx mov rax, qword ptr [rsp + 152] mov ecx, dword ptr [rsp - 76] add ecx, dword ptr [rax] mov dword ptr [rsp - 76], ecx mov rax, qword ptr [rsp + 144] mov ecx, dword ptr [rsp - 44] add ecx, dword ptr [rax] mov dword ptr [rsp - 44], ecx mov rax, qword ptr [rsp + 136] mov ecx, dword ptr [rsp - 68] add ecx, dword ptr [rax] mov dword ptr [rsp - 68], ecx mov rax, qword ptr [rsp + 128] mov ecx, dword ptr [rsp - 64] add ecx, dword ptr [rax] mov dword ptr [rsp - 64], ecx mov rax, qword ptr [rsp + 120] mov ecx, dword ptr [rsp - 60] add ecx, dword ptr [rax] mov dword ptr [rsp - 60], ecx mov rax, qword ptr [rsp + 112] mov ecx, dword ptr [rsp - 56] add ecx, dword ptr [rax] mov dword ptr [rsp - 56], ecx mov rax, qword ptr [rsp + 104] mov ecx, dword ptr [rsp - 48] add ecx, dword ptr [rax] mov dword ptr [rsp - 48], ecx mov rdi, qword ptr [rsp - 8] mov r12, qword ptr [rsp + 224] cmp rdi, r12 mov qword ptr [rsp + 96], rdi jne .LBB12_3 jmp .LBB12_2 .LBB12_40: mov eax, dword ptr [rsp - 88] add eax, dword ptr [rsp - 32] mov ecx, dword ptr [rsp - 72] add ecx, dword ptr [rsp - 100] add ecx, eax mov edx, dword ptr [rsp - 92] add edx, dword ptr [rsp - 96] mov eax, dword ptr [rsp - 52] add eax, edx add eax, ecx mov ecx, dword ptr [rsp - 80] add ecx, dword ptr [rsp - 84] mov edx, dword ptr [rsp - 76] add edx, ecx mov ecx, dword ptr [rsp - 44] add ecx, edx add ecx, eax mov edx, dword ptr [rsp - 64] add edx, dword ptr [rsp - 68] mov eax, dword ptr [rsp - 60] add eax, edx mov edx, dword ptr [rsp - 56] add edx, eax mov eax, dword ptr [rsp - 48] add eax, edx add eax, ecx add rsp, 240 .cfi_def_cfa_offset 56 pop rbx .cfi_def_cfa_offset 48 pop r12 .cfi_def_cfa_offset 40 pop r13 .cfi_def_cfa_offset 32 pop r14 .cfi_def_cfa_offset 24 pop r15 .cfi_def_cfa_offset 16 pop rbp .cfi_def_cfa_offset 8 ret ``` </details> to ```assembly simd_sum_slow: .cfi_startproc xor eax, eax cmp rsi, 16 jb .LBB12_4 shl rsi, 2 pxor xmm0, xmm0 pxor xmm1, xmm1 pxor xmm3, xmm3 pxor xmm2, xmm2 .p2align 4 .LBB12_2: movdqu xmm4, xmmword ptr [rdi] paddd xmm0, xmm4 movdqu xmm4, xmmword ptr [rdi + 16] paddd xmm1, xmm4 movdqu xmm4, xmmword ptr [rdi + 32] paddd xmm3, xmm4 movdqu xmm4, xmmword ptr [rdi + 48] paddd xmm2, xmm4 add rdi, 64 add rsi, -64 cmp rsi, 60 ja .LBB12_2 paddd xmm0, xmm3 paddd xmm1, xmm2 paddd xmm1, xmm0 pshufd xmm0, xmm1, 238 paddd xmm0, xmm1 pshufd xmm1, xmm0, 85 paddd xmm1, xmm0 movd eax, xmm1 .LBB12_4: ret ```
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…unk, r=Mark-Simulacrum optimize `slice::Iter::next_chunk` codegen for example (sourced from rust-lang#98326 (comment)) ```rust pub fn simd_sum_slow(arr: &[u32]) -> u32 { const STEP_SIZE: usize = 16; let mut result = [0; STEP_SIZE]; let mut iter = arr.iter(); while let Ok(c) = iter.next_chunk::<STEP_SIZE>() { for (&n, r) in c.iter().zip(result.iter_mut()) { *r += n; } } result.iter().sum() } ``` goes from (znver4) <details> <summary>many asm</summary> ```assembly simd_sum_slow: .cfi_startproc push rbp .cfi_def_cfa_offset 16 push r15 .cfi_def_cfa_offset 24 push r14 .cfi_def_cfa_offset 32 push r13 .cfi_def_cfa_offset 40 push r12 .cfi_def_cfa_offset 48 push rbx .cfi_def_cfa_offset 56 sub rsp, 240 .cfi_def_cfa_offset 296 .cfi_offset rbx, -56 .cfi_offset r12, -48 .cfi_offset r13, -40 .cfi_offset r14, -32 .cfi_offset r15, -24 .cfi_offset rbp, -16 lea r12, [rdi + 4*rsi] mov qword ptr [rsp - 32], 0 mov dword ptr [rsp - 88], 0 mov dword ptr [rsp - 100], 0 mov dword ptr [rsp - 72], 0 mov dword ptr [rsp - 96], 0 mov dword ptr [rsp - 92], 0 mov dword ptr [rsp - 52], 0 mov dword ptr [rsp - 84], 0 mov dword ptr [rsp - 80], 0 mov dword ptr [rsp - 76], 0 mov dword ptr [rsp - 44], 0 mov dword ptr [rsp - 68], 0 mov dword ptr [rsp - 64], 0 mov dword ptr [rsp - 60], 0 mov dword ptr [rsp - 56], 0 mov dword ptr [rsp - 48], 0 mov qword ptr [rsp + 224], r12 cmp rdi, r12 mov qword ptr [rsp + 96], rdi je .LBB12_2 .p2align 4 .LBB12_3: lea r13, [rdi + 4] cmp r13, r12 je .LBB12_4 lea r15, [rdi + 8] cmp r15, r12 je .LBB12_6 lea r14, [rdi + 12] cmp r14, r12 je .LBB12_8 lea rbx, [rdi + 16] cmp rbx, r12 je .LBB12_10 lea r11, [rdi + 20] cmp r11, r12 je .LBB12_12 lea r10, [rdi + 24] cmp r10, r12 je .LBB12_14 lea r9, [rdi + 28] cmp r9, r12 je .LBB12_16 lea r8, [rdi + 32] cmp r8, r12 je .LBB12_18 lea rax, [rdi + 36] cmp rax, r12 je .LBB12_20 mov qword ptr [rsp - 120], rax lea rax, [rdi + 40] mov qword ptr [rsp - 112], rax cmp rax, r12 je .LBB12_22 lea rdx, [rdi + 44] cmp rdx, r12 je .LBB12_24 lea rbp, [rdi + 48] cmp rbp, r12 je .LBB12_26 mov qword ptr [rsp - 40], r9 lea rcx, [rdi + 52] cmp rcx, r12 je .LBB12_30 lea r9, [rdi + 56] cmp r9, r12 je .LBB12_32 lea rax, [rdi + 60] cmp rax, r12 mov qword ptr [rsp - 24], r9 je .LBB12_34 mov qword ptr [rsp + 88], rax lea rax, [rdi + 64] mov qword ptr [rsp - 8], rax mov dword ptr [rsp - 128], 0 mov qword ptr [rsp - 16], rdi mov qword ptr [rsp + 56], r10 lea r10, [rsp + 216] mov qword ptr [rsp + 40], r10 mov qword ptr [rsp + 96], r13 lea rax, [rsp + 208] mov qword ptr [rsp + 32], rax mov qword ptr [rsp + 72], rdx lea rsi, [rsp + 200] mov qword ptr [rsp + 48], rbx lea rbx, [rsp + 192] mov qword ptr [rsp + 80], rcx lea rcx, [rsp + 184] mov qword ptr [rsp + 64], rbp lea rdx, [rsp + 176] mov qword ptr [rsp + 16], r14 lea r14, [rsp + 168] mov qword ptr [rsp + 24], r11 lea r11, [rsp + 160] lea r9, [rsp + 152] lea r12, [rsp + 144] lea r13, [rsp + 136] lea rbp, [rsp + 128] mov qword ptr [rsp], r15 lea r15, [rsp + 120] mov qword ptr [rsp + 8], r8 lea r8, [rsp + 112] lea rdi, [rsp + 104] jmp .LBB12_39 .p2align 4 .LBB12_2: mov qword ptr [rsp - 128], 0 jmp .LBB12_37 .p2align 4 .LBB12_4: mov eax, 1 mov qword ptr [rsp - 128], rax jmp .LBB12_37 .p2align 4 .LBB12_6: mov eax, 2 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_8: mov eax, 3 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_10: mov eax, 4 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_12: mov eax, 5 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_14: mov eax, 6 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_16: mov eax, 7 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_18: mov eax, 8 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_20: mov eax, 9 mov qword ptr [rsp - 128], rax jmp .LBB12_36 .LBB12_22: mov eax, 10 mov qword ptr [rsp - 128], rax mov rdi, qword ptr [rsp - 120] jmp .LBB12_36 .LBB12_24: mov eax, 11 mov qword ptr [rsp - 128], rax jmp .LBB12_27 .LBB12_26: mov eax, 12 mov qword ptr [rsp - 128], rax .LBB12_27: mov rsi, qword ptr [rsp - 112] mov rdi, qword ptr [rsp - 120] jmp .LBB12_36 .LBB12_30: mov rcx, rbp mov eax, 13 mov qword ptr [rsp - 128], rax jmp .LBB12_35 .LBB12_32: mov rax, rcx mov rcx, rbp mov esi, 14 mov qword ptr [rsp - 128], rsi jmp .LBB12_35 .LBB12_34: mov rax, rcx mov rcx, rbp mov esi, 15 mov qword ptr [rsp - 128], rsi .LBB12_35: mov rsi, qword ptr [rsp - 112] mov rdi, qword ptr [rsp - 120] mov r9, qword ptr [rsp - 40] .p2align 4 .LBB12_36: mov rbp, r13 .LBB12_37: mov r13, qword ptr [rsp - 24] mov qword ptr [rsp + 88], r13 mov r13, qword ptr [rsp - 128] mov qword ptr [rsp + 216], r13 mov r13b, 1 mov dword ptr [rsp - 128], r13d mov qword ptr [rsp - 24], rax mov qword ptr [rsp + 80], rcx mov qword ptr [rsp + 64], rdx mov qword ptr [rsp + 72], rsi mov qword ptr [rsp - 112], rdi mov qword ptr [rsp - 120], r8 mov qword ptr [rsp + 8], r9 mov qword ptr [rsp - 40], r10 mov qword ptr [rsp + 56], r11 mov qword ptr [rsp + 24], rbx mov qword ptr [rsp + 48], r14 mov qword ptr [rsp + 16], r15 mov qword ptr [rsp], rbp mov eax, 0 mov qword ptr [rsp - 16], rax mov qword ptr [rsp - 8], r12 lea r10, [rsp + 208] mov qword ptr [rsp + 40], r10 lea rax, [rsp + 200] mov qword ptr [rsp + 32], rax lea rsi, [rsp + 192] lea rbx, [rsp + 184] lea rcx, [rsp + 176] lea rdx, [rsp + 168] lea r14, [rsp + 160] lea r11, [rsp + 152] lea r9, [rsp + 144] lea r12, [rsp + 136] lea r13, [rsp + 128] lea rbp, [rsp + 120] lea r15, [rsp + 112] lea r8, [rsp + 104] lea rdi, [rsp + 232] .LBB12_39: mov r10, qword ptr [rsp + 96] mov rax, qword ptr [rsp + 40] mov qword ptr [rax], r10 mov rax, qword ptr [rsp + 32] mov r10, qword ptr [rsp] mov qword ptr [rax], r10 mov rax, qword ptr [rsp + 16] mov qword ptr [rsi], rax mov rax, qword ptr [rsp + 48] mov qword ptr [rbx], rax mov rax, qword ptr [rsp + 24] mov qword ptr [rcx], rax mov rax, qword ptr [rsp + 56] mov qword ptr [rdx], rax mov rax, qword ptr [rsp - 40] mov qword ptr [r14], rax mov rax, qword ptr [rsp + 8] mov qword ptr [r11], rax mov rax, qword ptr [rsp - 120] mov qword ptr [r9], rax mov rax, qword ptr [rsp - 112] mov qword ptr [r12], rax mov rax, qword ptr [rsp + 72] mov qword ptr [r13], rax mov rax, qword ptr [rsp + 64] mov qword ptr [rbp], rax mov rax, qword ptr [rsp + 80] mov qword ptr [r15], rax mov rax, qword ptr [rsp - 24] mov qword ptr [r8], rax mov rax, qword ptr [rsp + 88] mov qword ptr [rdi], rax cmp byte ptr [rsp - 128], 0 jne .LBB12_40 mov rax, qword ptr [rsp - 32] mov rcx, qword ptr [rsp - 16] add eax, dword ptr [rcx] mov qword ptr [rsp - 32], rax mov rax, qword ptr [rsp + 216] mov ecx, dword ptr [rsp - 88] add ecx, dword ptr [rax] mov dword ptr [rsp - 88], ecx mov rax, qword ptr [rsp + 208] mov ecx, dword ptr [rsp - 100] add ecx, dword ptr [rax] mov dword ptr [rsp - 100], ecx mov rax, qword ptr [rsp + 200] mov ecx, dword ptr [rsp - 72] add ecx, dword ptr [rax] mov dword ptr [rsp - 72], ecx mov rax, qword ptr [rsp + 192] mov ecx, dword ptr [rsp - 96] add ecx, dword ptr [rax] mov dword ptr [rsp - 96], ecx mov rax, qword ptr [rsp + 184] mov ecx, dword ptr [rsp - 92] add ecx, dword ptr [rax] mov dword ptr [rsp - 92], ecx mov rax, qword ptr [rsp + 176] mov ecx, dword ptr [rsp - 52] add ecx, dword ptr [rax] mov dword ptr [rsp - 52], ecx mov rax, qword ptr [rsp + 168] mov ecx, dword ptr [rsp - 84] add ecx, dword ptr [rax] mov dword ptr [rsp - 84], ecx mov rax, qword ptr [rsp + 160] mov ecx, dword ptr [rsp - 80] add ecx, dword ptr [rax] mov dword ptr [rsp - 80], ecx mov rax, qword ptr [rsp + 152] mov ecx, dword ptr [rsp - 76] add ecx, dword ptr [rax] mov dword ptr [rsp - 76], ecx mov rax, qword ptr [rsp + 144] mov ecx, dword ptr [rsp - 44] add ecx, dword ptr [rax] mov dword ptr [rsp - 44], ecx mov rax, qword ptr [rsp + 136] mov ecx, dword ptr [rsp - 68] add ecx, dword ptr [rax] mov dword ptr [rsp - 68], ecx mov rax, qword ptr [rsp + 128] mov ecx, dword ptr [rsp - 64] add ecx, dword ptr [rax] mov dword ptr [rsp - 64], ecx mov rax, qword ptr [rsp + 120] mov ecx, dword ptr [rsp - 60] add ecx, dword ptr [rax] mov dword ptr [rsp - 60], ecx mov rax, qword ptr [rsp + 112] mov ecx, dword ptr [rsp - 56] add ecx, dword ptr [rax] mov dword ptr [rsp - 56], ecx mov rax, qword ptr [rsp + 104] mov ecx, dword ptr [rsp - 48] add ecx, dword ptr [rax] mov dword ptr [rsp - 48], ecx mov rdi, qword ptr [rsp - 8] mov r12, qword ptr [rsp + 224] cmp rdi, r12 mov qword ptr [rsp + 96], rdi jne .LBB12_3 jmp .LBB12_2 .LBB12_40: mov eax, dword ptr [rsp - 88] add eax, dword ptr [rsp - 32] mov ecx, dword ptr [rsp - 72] add ecx, dword ptr [rsp - 100] add ecx, eax mov edx, dword ptr [rsp - 92] add edx, dword ptr [rsp - 96] mov eax, dword ptr [rsp - 52] add eax, edx add eax, ecx mov ecx, dword ptr [rsp - 80] add ecx, dword ptr [rsp - 84] mov edx, dword ptr [rsp - 76] add edx, ecx mov ecx, dword ptr [rsp - 44] add ecx, edx add ecx, eax mov edx, dword ptr [rsp - 64] add edx, dword ptr [rsp - 68] mov eax, dword ptr [rsp - 60] add eax, edx mov edx, dword ptr [rsp - 56] add edx, eax mov eax, dword ptr [rsp - 48] add eax, edx add eax, ecx add rsp, 240 .cfi_def_cfa_offset 56 pop rbx .cfi_def_cfa_offset 48 pop r12 .cfi_def_cfa_offset 40 pop r13 .cfi_def_cfa_offset 32 pop r14 .cfi_def_cfa_offset 24 pop r15 .cfi_def_cfa_offset 16 pop rbp .cfi_def_cfa_offset 8 ret ``` </details> to ```assembly simd_sum_slow: .cfi_startproc xor eax, eax cmp rsi, 16 jb .LBB12_4 shl rsi, 2 pxor xmm0, xmm0 pxor xmm1, xmm1 pxor xmm3, xmm3 pxor xmm2, xmm2 .p2align 4 .LBB12_2: movdqu xmm4, xmmword ptr [rdi] paddd xmm0, xmm4 movdqu xmm4, xmmword ptr [rdi + 16] paddd xmm1, xmm4 movdqu xmm4, xmmword ptr [rdi + 32] paddd xmm3, xmm4 movdqu xmm4, xmmword ptr [rdi + 48] paddd xmm2, xmm4 add rdi, 64 add rsi, -64 cmp rsi, 60 ja .LBB12_2 paddd xmm0, xmm3 paddd xmm1, xmm2 paddd xmm1, xmm0 pshufd xmm0, xmm1, 238 paddd xmm0, xmm1 pshufd xmm1, xmm0, 85 paddd xmm1, xmm0 movd eax, xmm1 .LBB12_4: ret ```
jhpratt added a commit
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Jul 29, 2026
…_simp, r=JohnTitor simplify `slice::Iter[Mut]::next_chunk` implementation I verified that this doesn't pessimize codegen using the example from the PR that inroduced the optimization of `next_chunk` (rust-lang#149131): ```rust #![feature(iter_next_chunk)] #[no_mangle] pub fn simd_sum_slow(arr: &[u32]) -> u32 { const STEP_SIZE: usize = 16; let mut result = [0; STEP_SIZE]; let mut iter = arr.iter(); while let Ok(c) = iter.next_chunk::<STEP_SIZE>() { for (&n, r) in c.iter().zip(result.iter_mut()) { *r += n; } } result.iter().sum() } ``` I compiled this example with ```shell ./build/host/stage1/bin/rustc t.rs --emit=asm -O --crate-type=lib ``` Before and after this change; the only difference is the choice of the jump instruction, which I think shouldn't make any difference: ```diff 28,29c28,29 < cmpq $64, %rsi < jae .LBB0_2 --- > cmpq $60, %rsi > ja .LBB0_2 ``` r? libs cc @bend-n
rust-timer added a commit
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Jul 29, 2026
Rollup merge of #158879 - WaffleLapkin:slice_iter_next_chunk_simp, r=JohnTitor simplify `slice::Iter[Mut]::next_chunk` implementation I verified that this doesn't pessimize codegen using the example from the PR that inroduced the optimization of `next_chunk` (#149131): ```rust #![feature(iter_next_chunk)] #[no_mangle] pub fn simd_sum_slow(arr: &[u32]) -> u32 { const STEP_SIZE: usize = 16; let mut result = [0; STEP_SIZE]; let mut iter = arr.iter(); while let Ok(c) = iter.next_chunk::<STEP_SIZE>() { for (&n, r) in c.iter().zip(result.iter_mut()) { *r += n; } } result.iter().sum() } ``` I compiled this example with ```shell ./build/host/stage1/bin/rustc t.rs --emit=asm -O --crate-type=lib ``` Before and after this change; the only difference is the choice of the jump instruction, which I think shouldn't make any difference: ```diff 28,29c28,29 < cmpq $64, %rsi < jae .LBB0_2 --- > cmpq $60, %rsi > ja .LBB0_2 ``` r? libs cc @bend-n
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codegen for example (sourced from #98326 (comment))
goes from (znver4)
many asm
to