Benchmark tests from Rust Book
I am getting odd results from microbenchmarks that can be reproduced with the the example bench_xor_1000_ints from the Rust Book chapter on Benchmark tests.
The section Gotcha: optimizations gives general recommendations to return a value from the Bencher::iter closure and/or to use the black_box function. I ended up with these five variants:
Benchmark code
#![feature(test)]
extern crate test;
use test::{Bencher, black_box};
fn xor(x: i32, y: i32) -> i32 { x ^ y }
#[bench]
fn xor_closure_a(b: &mut Bencher) {
b.iter(|| {
let n = black_box(1000);
(0..n).fold(0, |a, b| a ^ b)
});
}
#[bench]
fn xor_closure_b(b: &mut Bencher) {
b.iter(|| {
let n = black_box(1000);
(0..n).fold(0, |a, b| a ^ b);
});
}
#[bench]
fn xor_pointer_a(b: &mut Bencher) {
b.iter(|| {
let n = black_box(1000);
(0..n).fold(0, xor)
});
}
#[bench]
fn xor_pointer_b(b: &mut Bencher) {
b.iter(|| {
let n = black_box(1000);
(0..n).fold(0, xor);
});
}
#[bench] // closure/pointer or semicolon doesn't affect results
fn xor_black_box(b: &mut Bencher) {
b.iter(|| {
black_box((0..1000).fold(0, xor));
});
}
Benchmark naming
- prefix xor_closure_: pass closure
|a, b| a ^ b - prefix xor_pointer_: pass function pointer
xor - suffix _a:
b.iterclosure returns value (note lack of semicolon) - suffix _b:
b.iterclosure doesn't return value (ends with semicolon) - xor_black_box: throw everything into
black_boxand hope for the best
Benchmark results
test tests::xor_black_box ... bench: 69 ns/iter (+/- 1)
test tests::xor_closure_a ... bench: 70 ns/iter (+/- 1)
test tests::xor_closure_b ... bench: 921 ns/iter (+/- 5)
test tests::xor_pointer_a ... bench: 60 ns/iter (+/- 1)
test tests::xor_pointer_b ... bench: 0 ns/iter (+/- 0)
Some observations regarding measurements:
- Removal of the black-boxed iteration counter
let n = black_box(1000)and inlining it into range(0..1000).fold ...doesn't affect any of the results - Scaling of the iteration counter
nscales measurements appropriately (except forxor_pointer_boptimized to 0)
On the whole, results agree with the general recommendations from Rust Book, except for xor_closure_b benchmark.
More specifically, results with the suffix _a (that return a value) seem to agree with the black-boxed xor_black_box which sounds good to me. And xor_pointer_b optimized to 0 seems legit since its closure doesn't return the value. But the result of xor_closure_b is odd.
Assembly code may clarify this question. How can I prevent the Rust benchmark library from optimizing away my code? gives a good overview on reading assembly from the Rust benchmark tests.
cargo rustc --release -- --emit asm
produces this output:
.text
.file "fpinrust.cgu-0.rs"
.section .rodata.cst16,"aM",@progbits,16
.p2align 4
.LCPI0_0:
.long 0
.long 1
.long 2
.long 3
.LCPI0_1:
.long 4
.long 4
.long 4
.long 4
.LCPI0_2:
.long 8
.long 8
.long 8
.long 8
.LCPI0_3:
.long 12
.long 12
.long 12
.long 12
.LCPI0_4:
.long 16
.long 16
.long 16
.long 16
.LCPI0_5:
.long 20
.long 20
.long 20
.long 20
.LCPI0_6:
.long 24
.long 24
.long 24
.long 24
.LCPI0_7:
.long 28
.long 28
.long 28
.long 28
.LCPI0_8:
.long 32
.long 32
.long 32
.long 32
.section .text._ZN8fpinrust5tests13xor_closure_a17h4df097d1e565a700E,"ax",@progbits
.globl _ZN8fpinrust5tests13xor_closure_a17h4df097d1e565a700E
.p2align 4, 0x90
.type _ZN8fpinrust5tests13xor_closure_a17h4df097d1e565a700E,@function
_ZN8fpinrust5tests13xor_closure_a17h4df097d1e565a700E:
.cfi_startproc
pushq %r14
.Ltmp0:
.cfi_def_cfa_offset 16
pushq %rbx
.Ltmp1:
.cfi_def_cfa_offset 24
subq $40, %rsp
.Ltmp2:
.cfi_def_cfa_offset 64
.Ltmp3:
.cfi_offset %rbx, -24
.Ltmp4:
.cfi_offset %r14, -16
movq %rdi, %r14
leaq 24(%rsp), %rdi
callq _ZN3std4time7Instant3now17h37bccd496c61083dE@PLT
movq (%r14), %r9
testq %r9, %r9
je .LBB0_15
xorl %ecx, %ecx
leaq 8(%rsp), %r8
movdqa .LCPI0_0(%rip), %xmm8
movdqa .LCPI0_1(%rip), %xmm15
movdqa .LCPI0_2(%rip), %xmm2
movdqa .LCPI0_3(%rip), %xmm9
movdqa .LCPI0_4(%rip), %xmm10
movdqa .LCPI0_5(%rip), %xmm11
movdqa .LCPI0_6(%rip), %xmm12
movdqa .LCPI0_7(%rip), %xmm13
movdqa .LCPI0_8(%rip), %xmm14
.p2align 4, 0x90
.LBB0_2:
incq %rcx
movl $1000, 8(%rsp)
#APP
#NO_APP
movl 8(%rsp), %esi
testl %esi, %esi
movl $0, %edx
jle .LBB0_14
xorl %edx, %edx
cmpl $8, %esi
jae .LBB0_5
xorl %edi, %edi
jmp .LBB0_13
.p2align 4, 0x90
.LBB0_5:
movl %esi, %eax
andl $-8, %eax
movl $0, %edi
je .LBB0_13
leal -8(%rax), %edx
movl %edx, %edi
shrl $3, %edi
leal 1(%rdi), %ebx
andl $3, %ebx
pxor %xmm3, %xmm3
cmpl $24, %edx
pxor %xmm4, %xmm4
movdqa %xmm8, %xmm5
jb .LBB0_9
leal -1(%rbx), %edx
subl %edi, %edx
pxor %xmm3, %xmm3
pxor %xmm4, %xmm4
movdqa %xmm8, %xmm5
.p2align 4, 0x90
.LBB0_8:
movdqa %xmm5, %xmm6
paddd %xmm15, %xmm6
movdqa %xmm5, %xmm7
paddd %xmm2, %xmm7
pxor %xmm5, %xmm3
pxor %xmm4, %xmm6
movdqa %xmm5, %xmm4
paddd %xmm9, %xmm4
movdqa %xmm5, %xmm0
paddd %xmm10, %xmm0
pxor %xmm7, %xmm3
movdqa %xmm5, %xmm7
paddd %xmm11, %xmm7
movdqa %xmm5, %xmm1
paddd %xmm12, %xmm1
pxor %xmm4, %xmm7
pxor %xmm6, %xmm7
movdqa %xmm5, %xmm4
paddd %xmm13, %xmm4
paddd %xmm14, %xmm5
pxor %xmm0, %xmm1
pxor %xmm1, %xmm3
pxor %xmm7, %xmm4
addl $4, %edx
jne .LBB0_8
.LBB0_9:
testl %ebx, %ebx
je .LBB0_12
negl %ebx
.p2align 4, 0x90
.LBB0_11:
movdqa %xmm5, %xmm0
pxor %xmm5, %xmm3
paddd %xmm15, %xmm5
paddd %xmm2, %xmm0
pxor %xmm5, %xmm4
incl %ebx
movdqa %xmm0, %xmm5
jne .LBB0_11
.LBB0_12:
pxor %xmm4, %xmm3
pshufd $78, %xmm3, %xmm0
pxor %xmm3, %xmm0
pshufd $229, %xmm0, %xmm1
pxor %xmm0, %xmm1
movd %xmm1, %edx
cmpl %eax, %esi
movl %eax, %edi
je .LBB0_14
.p2align 4, 0x90
.LBB0_13:
xorl %edi, %edx
leal 1(%rdi), %eax
cmpl %eax, %esi
movl %eax, %edi
jne .LBB0_13
.LBB0_14:
movl %edx, 8(%rsp)
#APP
#NO_APP
cmpq %r9, %rcx
jne .LBB0_2
.LBB0_15:
leaq 8(%rsp), %rdi
leaq 24(%rsp), %rsi
callq _ZN3std4time7Instant7elapsed17h0b6076720ddfcc2bE@PLT
movq 8(%rsp), %rax
movl 16(%rsp), %ecx
movq %rax, 8(%r14)
movl %ecx, 16(%r14)
addq $40, %rsp
popq %rbx
popq %r14
retq
.Lfunc_end0:
.size _ZN8fpinrust5tests13xor_closure_a17h4df097d1e565a700E, .Lfunc_end0-_ZN8fpinrust5tests13xor_closure_a17h4df097d1e565a700E
.cfi_endproc
.section .text._ZN8fpinrust5tests13xor_closure_b17h4bdd5e59e5c19a55E,"ax",@progbits
.globl _ZN8fpinrust5tests13xor_closure_b17h4bdd5e59e5c19a55E
.p2align 4, 0x90
.type _ZN8fpinrust5tests13xor_closure_b17h4bdd5e59e5c19a55E,@function
_ZN8fpinrust5tests13xor_closure_b17h4bdd5e59e5c19a55E:
.cfi_startproc
pushq %r14
.Ltmp5:
.cfi_def_cfa_offset 16
pushq %rbx
.Ltmp6:
.cfi_def_cfa_offset 24
subq $40, %rsp
.Ltmp7:
.cfi_def_cfa_offset 64
.Ltmp8:
.cfi_offset %rbx, -24
.Ltmp9:
.cfi_offset %r14, -16
movq %rdi, %r14
leaq 24(%rsp), %rdi
callq _ZN3std4time7Instant3now17h37bccd496c61083dE@PLT
movq (%r14), %rax
testq %rax, %rax
je .LBB1_5
xorl %ecx, %ecx
leaq 8(%rsp), %rdx
.p2align 4, 0x90
.LBB1_2:
movl $1000, 8(%rsp)
#APP
#NO_APP
movl 8(%rsp), %esi
xorl %ebx, %ebx
.p2align 4, 0x90
.LBB1_3:
xorl %edi, %edi
cmpl %esi, %ebx
setl %dil
addl %ebx, %edi
cmpl %esi, %ebx
movl %edi, %ebx
jl .LBB1_3
incq %rcx
#APP
#NO_APP
cmpq %rax, %rcx
jne .LBB1_2
.LBB1_5:
leaq 8(%rsp), %rdi
leaq 24(%rsp), %rsi
callq _ZN3std4time7Instant7elapsed17h0b6076720ddfcc2bE@PLT
movq 8(%rsp), %rax
movl 16(%rsp), %ecx
movq %rax, 8(%r14)
movl %ecx, 16(%r14)
addq $40, %rsp
popq %rbx
popq %r14
retq
.Lfunc_end1:
.size _ZN8fpinrust5tests13xor_closure_b17h4bdd5e59e5c19a55E, .Lfunc_end1-_ZN8fpinrust5tests13xor_closure_b17h4bdd5e59e5c19a55E
.cfi_endproc
.section .rodata.cst16,"aM",@progbits,16
.p2align 4
.LCPI2_0:
.long 0
.long 1
.long 2
.long 3
.LCPI2_1:
.long 4
.long 4
.long 4
.long 4
.LCPI2_2:
.long 8
.long 8
.long 8
.long 8
.LCPI2_3:
.long 12
.long 12
.long 12
.long 12
.LCPI2_4:
.long 16
.long 16
.long 16
.long 16
.LCPI2_5:
.long 20
.long 20
.long 20
.long 20
.LCPI2_6:
.long 24
.long 24
.long 24
.long 24
.LCPI2_7:
.long 28
.long 28
.long 28
.long 28
.LCPI2_8:
.long 32
.long 32
.long 32
.long 32
.section .text._ZN8fpinrust5tests13xor_pointer_a17hca6c00df2b597ce7E,"ax",@progbits
.globl _ZN8fpinrust5tests13xor_pointer_a17hca6c00df2b597ce7E
.p2align 4, 0x90
.type _ZN8fpinrust5tests13xor_pointer_a17hca6c00df2b597ce7E,@function
_ZN8fpinrust5tests13xor_pointer_a17hca6c00df2b597ce7E:
.cfi_startproc
pushq %r14
.Ltmp10:
.cfi_def_cfa_offset 16
pushq %rbx
.Ltmp11:
.cfi_def_cfa_offset 24
subq $40, %rsp
.Ltmp12:
.cfi_def_cfa_offset 64
.Ltmp13:
.cfi_offset %rbx, -24
.Ltmp14:
.cfi_offset %r14, -16
movq %rdi, %r14
leaq 24(%rsp), %rdi
callq _ZN3std4time7Instant3now17h37bccd496c61083dE@PLT
movq (%r14), %r9
testq %r9, %r9
je .LBB2_15
xorl %ecx, %ecx
leaq 8(%rsp), %r8
movdqa .LCPI2_0(%rip), %xmm8
movdqa .LCPI2_1(%rip), %xmm15
movdqa .LCPI2_2(%rip), %xmm2
movdqa .LCPI2_3(%rip), %xmm9
movdqa .LCPI2_4(%rip), %xmm10
movdqa .LCPI2_5(%rip), %xmm11
movdqa .LCPI2_6(%rip), %xmm12
movdqa .LCPI2_7(%rip), %xmm13
movdqa .LCPI2_8(%rip), %xmm14
.p2align 4, 0x90
.LBB2_2:
incq %rcx
movl $1000, 8(%rsp)
#APP
#NO_APP
movl 8(%rsp), %esi
testl %esi, %esi
movl $0, %edx
jle .LBB2_14
xorl %edx, %edx
cmpl $8, %esi
jae .LBB2_5
xorl %edi, %edi
jmp .LBB2_13
.p2align 4, 0x90
.LBB2_5:
movl %esi, %eax
andl $-8, %eax
movl $0, %edi
je .LBB2_13
leal -8(%rax), %edx
movl %edx, %edi
shrl $3, %edi
leal 1(%rdi), %ebx
andl $3, %ebx
pxor %xmm3, %xmm3
cmpl $24, %edx
pxor %xmm4, %xmm4
movdqa %xmm8, %xmm5
jb .LBB2_9
leal -1(%rbx), %edx
subl %edi, %edx
pxor %xmm3, %xmm3
pxor %xmm4, %xmm4
movdqa %xmm8, %xmm5
.p2align 4, 0x90
.LBB2_8:
movdqa %xmm5, %xmm6
paddd %xmm15, %xmm6
movdqa %xmm5, %xmm7
paddd %xmm2, %xmm7
pxor %xmm5, %xmm3
pxor %xmm4, %xmm6
movdqa %xmm5, %xmm4
paddd %xmm9, %xmm4
movdqa %xmm5, %xmm0
paddd %xmm10, %xmm0
pxor %xmm7, %xmm3
movdqa %xmm5, %xmm7
paddd %xmm11, %xmm7
movdqa %xmm5, %xmm1
paddd %xmm12, %xmm1
pxor %xmm4, %xmm7
pxor %xmm6, %xmm7
movdqa %xmm5, %xmm4
paddd %xmm13, %xmm4
paddd %xmm14, %xmm5
pxor %xmm0, %xmm1
pxor %xmm1, %xmm3
pxor %xmm7, %xmm4
addl $4, %edx
jne .LBB2_8
.LBB2_9:
testl %ebx, %ebx
je .LBB2_12
negl %ebx
.p2align 4, 0x90
.LBB2_11:
movdqa %xmm5, %xmm0
pxor %xmm5, %xmm3
paddd %xmm15, %xmm5
paddd %xmm2, %xmm0
pxor %xmm5, %xmm4
incl %ebx
movdqa %xmm0, %xmm5
jne .LBB2_11
.LBB2_12:
pxor %xmm4, %xmm3
pshufd $78, %xmm3, %xmm0
pxor %xmm3, %xmm0
pshufd $229, %xmm0, %xmm1
pxor %xmm0, %xmm1
movd %xmm1, %edx
cmpl %eax, %esi
movl %eax, %edi
je .LBB2_14
.p2align 4, 0x90
.LBB2_13:
xorl %edi, %edx
leal 1(%rdi), %eax
cmpl %eax, %esi
movl %eax, %edi
jne .LBB2_13
.LBB2_14:
movl %edx, 8(%rsp)
#APP
#NO_APP
cmpq %r9, %rcx
jne .LBB2_2
.LBB2_15:
leaq 8(%rsp), %rdi
leaq 24(%rsp), %rsi
callq _ZN3std4time7Instant7elapsed17h0b6076720ddfcc2bE@PLT
movq 8(%rsp), %rax
movl 16(%rsp), %ecx
movq %rax, 8(%r14)
movl %ecx, 16(%r14)
addq $40, %rsp
popq %rbx
popq %r14
retq
.Lfunc_end2:
.size _ZN8fpinrust5tests13xor_pointer_a17hca6c00df2b597ce7E, .Lfunc_end2-_ZN8fpinrust5tests13xor_pointer_a17hca6c00df2b597ce7E
.cfi_endproc
.section .text._ZN8fpinrust5tests13xor_pointer_b17h4ef66678d6655ef4E,"ax",@progbits
.globl _ZN8fpinrust5tests13xor_pointer_b17h4ef66678d6655ef4E
.p2align 4, 0x90
.type _ZN8fpinrust5tests13xor_pointer_b17h4ef66678d6655ef4E,@function
_ZN8fpinrust5tests13xor_pointer_b17h4ef66678d6655ef4E:
.cfi_startproc
pushq %rbx
.Ltmp15:
.cfi_def_cfa_offset 16
subq $32, %rsp
.Ltmp16:
.cfi_def_cfa_offset 48
.Ltmp17:
.cfi_offset %rbx, -16
movq %rdi, %rbx
leaq 16(%rsp), %rdi
callq _ZN3std4time7Instant3now17h37bccd496c61083dE@PLT
movq (%rbx), %rax
testq %rax, %rax
je .LBB3_3
leaq (%rsp), %rcx
.p2align 4, 0x90
.LBB3_2:
movl $1000, (%rsp)
#APP
#NO_APP
#APP
#NO_APP
decq %rax
jne .LBB3_2
.LBB3_3:
leaq (%rsp), %rdi
leaq 16(%rsp), %rsi
callq _ZN3std4time7Instant7elapsed17h0b6076720ddfcc2bE@PLT
movq (%rsp), %rax
movl 8(%rsp), %ecx
movq %rax, 8(%rbx)
movl %ecx, 16(%rbx)
addq $32, %rsp
popq %rbx
retq
.Lfunc_end3:
.size _ZN8fpinrust5tests13xor_pointer_b17h4ef66678d6655ef4E, .Lfunc_end3-_ZN8fpinrust5tests13xor_pointer_b17h4ef66678d6655ef4E
.cfi_endproc
.section .rodata.cst16,"aM",@progbits,16
.p2align 4
.LCPI4_0:
.long 0
.long 1
.long 2
.long 3
.LCPI4_1:
.long 4
.long 4
.long 4
.long 4
.LCPI4_2:
.long 8
.long 8
.long 8
.long 8
.LCPI4_3:
.long 12
.long 12
.long 12
.long 12
.LCPI4_4:
.long 16
.long 16
.long 16
.long 16
.LCPI4_5:
.long 20
.long 20
.long 20
.long 20
.LCPI4_6:
.long 24
.long 24
.long 24
.long 24
.LCPI4_7:
.long 28
.long 28
.long 28
.long 28
.LCPI4_8:
.long 32
.long 32
.long 32
.long 32
.LCPI4_9:
.long 36
.long 36
.long 36
.long 36
.LCPI4_10:
.long 40
.long 40
.long 40
.long 40
.section .text._ZN8fpinrust5tests13xor_black_box17h8af7e6f80fe83dc8E,"ax",@progbits
.globl _ZN8fpinrust5tests13xor_black_box17h8af7e6f80fe83dc8E
.p2align 4, 0x90
.type _ZN8fpinrust5tests13xor_black_box17h8af7e6f80fe83dc8E,@function
_ZN8fpinrust5tests13xor_black_box17h8af7e6f80fe83dc8E:
.cfi_startproc
pushq %rbx
.Ltmp18:
.cfi_def_cfa_offset 16
subq $32, %rsp
.Ltmp19:
.cfi_def_cfa_offset 48
.Ltmp20:
.cfi_offset %rbx, -16
movq %rdi, %rbx
leaq 16(%rsp), %rdi
callq _ZN3std4time7Instant3now17h37bccd496c61083dE@PLT
movq (%rbx), %rax
testq %rax, %rax
je .LBB4_5
xorl %ecx, %ecx
movdqa .LCPI4_1(%rip), %xmm9
movdqa .LCPI4_2(%rip), %xmm10
movdqa .LCPI4_3(%rip), %xmm11
movdqa .LCPI4_4(%rip), %xmm12
movdqa .LCPI4_5(%rip), %xmm13
movdqa .LCPI4_6(%rip), %xmm14
movdqa .LCPI4_7(%rip), %xmm15
movdqa .LCPI4_8(%rip), %xmm0
movdqa .LCPI4_9(%rip), %xmm1
movdqa .LCPI4_10(%rip), %xmm2
leaq (%rsp), %rdx
.p2align 4, 0x90
.LBB4_2:
pxor %xmm3, %xmm3
movl $1000, %esi
pxor %xmm4, %xmm4
movdqa .LCPI4_0(%rip), %xmm5
.p2align 4, 0x90
.LBB4_3:
movdqa %xmm5, %xmm6
paddd %xmm9, %xmm6
movdqa %xmm5, %xmm7
paddd %xmm10, %xmm7
pxor %xmm5, %xmm3
pxor %xmm4, %xmm6
movdqa %xmm5, %xmm4
paddd %xmm11, %xmm4
pxor %xmm7, %xmm3
movdqa %xmm5, %xmm7
paddd %xmm13, %xmm7
pxor %xmm4, %xmm7
movdqa %xmm5, %xmm4
paddd %xmm12, %xmm4
pxor %xmm6, %xmm7
movdqa %xmm5, %xmm6
paddd %xmm14, %xmm6
pxor %xmm4, %xmm6
movdqa %xmm5, %xmm8
paddd %xmm15, %xmm8
pxor %xmm6, %xmm3
movdqa %xmm5, %xmm4
paddd %xmm0, %xmm4
pxor %xmm4, %xmm3
movdqa %xmm5, %xmm4
paddd %xmm1, %xmm4
pxor %xmm8, %xmm4
pxor %xmm7, %xmm4
paddd %xmm2, %xmm5
addl $-40, %esi
jne .LBB4_3
pxor %xmm3, %xmm4
pshufd $78, %xmm4, %xmm3
pxor %xmm4, %xmm3
pshufd $229, %xmm3, %xmm4
pxor %xmm3, %xmm4
incq %rcx
movd %xmm4, (%rsp)
#APP
#NO_APP
#APP
#NO_APP
cmpq %rax, %rcx
jne .LBB4_2
.LBB4_5:
leaq (%rsp), %rdi
leaq 16(%rsp), %rsi
callq _ZN3std4time7Instant7elapsed17h0b6076720ddfcc2bE@PLT
movq (%rsp), %rax
movl 8(%rsp), %ecx
movq %rax, 8(%rbx)
movl %ecx, 16(%rbx)
addq $32, %rsp
popq %rbx
retq
.Lfunc_end4:
.size _ZN8fpinrust5tests13xor_black_box17h8af7e6f80fe83dc8E, .Lfunc_end4-_ZN8fpinrust5tests13xor_black_box17h8af7e6f80fe83dc8E
.cfi_endproc
.section ".note.GNU-stack","",@progbits
Looking at the assembly, xor_closure_a, xor_pointer_a and xor_black_box which all have relatively the same performance, evaluate to similar assembly code. Which is, by the way, a lot more instructions than the amount of ASM for poor xor_closure_b.
This is where my research ends. I would be glad if someone explains, why this blanket of assembly produced by xor_black_box evaluates faster than xor_closure_b. Or put it differently, why the version that should be optimized away by the compiler runs notably slower, and which benchmark variant I should trust?
Versions
rustc --version
rustc 1.13.0-nightly (378195665 2016-09-08)
cargo --version
cargo 0.13.0-nightly (afaffa1 2016-09-06)
Update
@Francis Gagné did a fantastic job to investigate the issue in his answer. The steps that took me to reproduce his results are listed below.
Compile benchmarks and emit assembly:
cargo rustc --release -- --test --emit asm
Run produced executable to verify previous behavior:
./target/release/deps/xor --bench
running 2 tests
test tests::xor_closure_b ... bench: 925 ns/iter (+/- 9)
test tests::xor_pointer_b ... bench: 0 ns/iter (+/- 0)
test result: ok. 0 passed; 0 failed; 0 ignored; 2 measured
Compile patched assembly output ./target/release/deps/xor.s
export RUSTLIB=/path/to/lib/rustlib
gcc target/release/deps/xor.s $RUSTLIB/x86_64-unknown-linux-gnu/lib/*.rlib $RUSTLIB/x86_64-unknown-linux-gnu/lib/*.so -pthread -lpthread -lm -ldl
Run updated benchmarks:
./a.out --bench
running 2 tests
test tests::xor_closure_b ... bench: 1 ns/iter (+/- 0)
test tests::xor_pointer_b ... bench: 0 ns/iter (+/- 0)
test result: ok. 0 passed; 0 failed; 0 ignored; 2 measured
