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Make ptr range iterable #91000

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wants to merge 7 commits into from
Closed

Make ptr range iterable #91000

wants to merge 7 commits into from

Commits on Nov 18, 2021

  1. Make ptr range iterable

    @dtolnay
    dtolnay committed Nov 18, 2021
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  2. More ptr range test cases

    @dtolnay
    dtolnay committed Nov 18, 2021
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  3. Document alignedness of ptr range elements

    @dtolnay
    dtolnay committed Nov 18, 2021
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  4. Add ui test of ptr range coercion

    @dtolnay
    dtolnay committed Nov 18, 2021
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  5. Document add/get_unchecked alternatives

    @dtolnay
    dtolnay committed Nov 18, 2021
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  6. Err(0) is no longer going to be okay following PR 89916

    @dtolnay
    dtolnay committed Nov 18, 2021
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  7. Produce better machine code for a loop over ptr range 

    Test code:

    extern "C" {
        fn foreign(ptr: *const i32);
    }

    pub fn forloop(start: *const i32, end: *const i32) {
        for ptr in start..end {
            unsafe { foreign(ptr) }
        }
    }

Before:

    asm::forloop:
      push    r15
      push    r14
      push    rbx
      cmp     rdi, rsi
      jae     .LBB0_3
      mov     r15, rsi
      mov     r14, qword, ptr, [rip, +, foreign@GOTPCREL]
    .LBB0_2:
      lea     rax, [rdi, +, 4]
      cmp     rax, r15
      mov     rbx, r15
      cmovb   rbx, rax
      cmp     rdi, rax
      cmova   rbx, r15
      call    r14
      mov     rdi, rbx
      cmp     rbx, r15
      jb      .LBB0_2
    .LBB0_3:
      pop     rbx
      pop     r14
      pop     r15
      ret

After:

    asm::forloop:
      push    r15
      push    r14
      push    rbx
      cmp     rdi, rsi
      jae     .LBB0_3
      mov     r15, rsi
      mov     r14, qword, ptr, [rip, +, foreign@GOTPCREL]
    .LBB0_2:
      mov     rax, r15
      sub     rax, rdi
      lea     rbx, [rdi, +, 4]
      cmp     rax, 4
      cmovb   rbx, r15
      call    r14
      mov     rdi, rbx
      cmp     rbx, r15
      jb      .LBB0_2
    .LBB0_3:
      pop     rbx
      pop     r14
      pop     r15
      ret
    @dtolnay
    dtolnay committed Nov 18, 2021
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