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pointer arithmetic should use GEP #8118

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thestinger opened this issue Jul 29, 2013 · 0 comments
Closed

pointer arithmetic should use GEP #8118

thestinger opened this issue Jul 29, 2013 · 0 comments
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I-slow Issue: Problems and improvements with respect to performance of generated code.

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@thestinger
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Using and ptrtoint and inttoptr throws out all the aliasing information gathered by LLVM, it's the cause of issue #7136 and overall has a major impact on looping performance.
@thestinger thestinger mentioned this issue Jul 30, 2013
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bors added a commit that referenced this issue Jul 30, 2013
@bors
auto merge of #8121 : thestinger/rust/offset, r=alexcrichton
576f395 
Closes #8118, #7136

~~~rust
extern mod extra;

use std::vec;
use std::ptr;

fn bench_from_elem(b: &mut extra::test::BenchHarness) {
    do b.iter {
        let v: ~[u8] = vec::from_elem(1024, 0u8);
    }
}

fn bench_set_memory(b: &mut extra::test::BenchHarness) {
    do b.iter {
        let mut v: ~[u8] = vec::with_capacity(1024);
        unsafe {
            let vp = vec::raw::to_mut_ptr(v);
            ptr::set_memory(vp, 0, 1024);
            vec::raw::set_len(&mut v, 1024);
        }
    }
}

fn bench_vec_repeat(b: &mut extra::test::BenchHarness) {
    do b.iter {
        let v: ~[u8] = ~[0u8, ..1024];
    }
}
~~~

Before:

    test bench_from_elem ... bench: 415 ns/iter (+/- 17)
    test bench_set_memory ... bench: 85 ns/iter (+/- 4)
    test bench_vec_repeat ... bench: 83 ns/iter (+/- 3)

After:

    test bench_from_elem ... bench: 84 ns/iter (+/- 2)
    test bench_set_memory ... bench: 84 ns/iter (+/- 5)
    test bench_vec_repeat ... bench: 84 ns/iter (+/- 3)
@bluss bluss mentioned this issue Feb 9, 2015
Closed
flip1995 pushed a commit to flip1995/rust that referenced this issue Jan 27, 2023
@bors
Auto merge of rust-lang#10218 - Alexendoo:bool-assert-comparison-sugg…
e0ee58b 
…estion, r=dswij

Add machine applicable suggestion for `bool_assert_comparison`

Fixes rust-lang#7598
Also closes rust-lang#8118, it had already been fixed by an earlier change but I've added a test for it

changelog: [`bool_assert_comparison`] The suggestion is now machine applicable
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implement pointer arithmetic with GEP
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@thestinger