Created
January 6, 2015 12:57
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| pub struct MySlice { | |
| start: *const u8, | |
| len: uint, | |
| } | |
| #[inline(never)] | |
| pub fn merge_slice(val: &[u8]) -> MySlice { | |
| let mut val_ptr = val.as_ptr(); | |
| let mut len = val.len(); | |
| let mut state = unsafe { | |
| MySlice { | |
| start: val_ptr, | |
| len: 0, | |
| } | |
| }; | |
| unsafe { | |
| while len != 0 { | |
| let mut tmp1 = val_ptr; | |
| let mut tmp2 = val_ptr; | |
| loop { | |
| tmp1 = tmp1.offset(1); | |
| tmp2 = tmp2.offset(1); | |
| len -= 1; | |
| state.len += 1; | |
| if tmp1 != tmp2 { | |
| black_box(&state); | |
| val_ptr = tmp2; | |
| state = MySlice { | |
| start: val_ptr, | |
| len: 0, | |
| }; | |
| break; | |
| } | |
| if len == 0 { | |
| return state; | |
| } | |
| } | |
| } | |
| } | |
| state | |
| } | |
| fn main() { | |
| let mut val_slice: &[u8] = &[12, 23, 34, 45, 12]; | |
| let mut r = &val_slice; | |
| black_box(&merge_slice(*r)); | |
| } |
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| ; Function Attrs: noinline nounwind uwtable | |
| define internal fastcc void @_ZN11merge_slice20ha8074868c3655a38MdaE(%struct.MySlice* noalias nocapture sret dereferenceable(16), { i8*, i64 }* noalias nocapture dereferenceable(16)) unnamed_addr #1 { | |
| entry-block: | |
| %state = alloca %struct.MySlice, align 8 | |
| %2 = bitcast { i8*, i64 }* %1 to i8* | |
| %arg.sroa.0.0..sroa_idx = getelementptr inbounds { i8*, i64 }* %1, i64 0, i32 0 | |
| %arg.sroa.0.0.copyload = load i8** %arg.sroa.0.0..sroa_idx, align 8 | |
| %arg.sroa.5.0..sroa_idx32 = getelementptr inbounds { i8*, i64 }* %1, i64 0, i32 1 | |
| %arg1.sroa.4.0.copyload = load i64* %arg.sroa.5.0..sroa_idx32, align 8 | |
| %3 = bitcast %struct.MySlice* %state to i8* | |
| call void @llvm.lifetime.start(i64 16, i8* %3) | |
| %4 = getelementptr inbounds %struct.MySlice* %state, i64 0, i32 0 | |
| store i8* %arg.sroa.0.0.copyload, i8** %4, align 8 | |
| %5 = getelementptr inbounds %struct.MySlice* %state, i64 0, i32 1 | |
| store i64 0, i64* %5, align 8 | |
| %6 = icmp eq i64 %arg1.sroa.4.0.copyload, 0 | |
| br i1 %6, label %while_exit, label %next-block.preheader | |
| next-block.preheader: ; preds = %entry-block | |
| br label %next-block | |
| while_exit: ; preds = %entry-block | |
| %7 = bitcast %struct.MySlice* %0 to i8* | |
| call void @llvm.memcpy.p0i8.p0i8.i64(i8* %7, i8* %3, i64 16, i32 8, i1 false) | |
| call void @llvm.lifetime.end(i64 16, i8* %3) | |
| br label %clean_custom_ | |
| next-block: ; preds = %next-block.preheader, %next-block | |
| %8 = phi i64 [ %10, %next-block ], [ 0, %next-block.preheader ] | |
| %len.1 = phi i64 [ %9, %next-block ], [ %arg1.sroa.4.0.copyload, %next-block.preheader ] | |
| %9 = add i64 %len.1, -1 | |
| %10 = add i64 %8, 1 | |
| %11 = icmp eq i64 %9, 0 | |
| br i1 %11, label %then-block-319-, label %next-block | |
| then-block-319-: ; preds = %next-block | |
| %.lcssa = phi i64 [ %10, %next-block ] | |
| store i64 %.lcssa, i64* %5, align 8 | |
| %12 = bitcast %struct.MySlice* %0 to i8* | |
| call void @llvm.memcpy.p0i8.p0i8.i64(i8* %12, i8* %3, i64 16, i32 8, i1 false) | |
| call void @llvm.lifetime.end(i64 16, i8* %3) | |
| br label %clean_custom_ | |
| clean_custom_: ; preds = %while_exit, %then-block-319- | |
| call void @llvm.lifetime.end(i64 16, i8* %2) | |
| ret void | |
| } |
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| _ZN11merge_slice20ha8074868c3655a38MdaE: | |
| .cfi_startproc | |
| cmpq %fs:112, %rsp | |
| ja .LBB0_2 | |
| movabsq $16, %r10 | |
| movabsq $0, %r11 | |
| callq __morestack | |
| retq | |
| .LBB0_2: | |
| subq $16, %rsp | |
| .Ltmp0: | |
| .cfi_def_cfa_offset 24 | |
| movq (%rsi), %rcx | |
| movq 8(%rsi), %rax | |
| movq %rcx, (%rsp) | |
| movq $0, 8(%rsp) | |
| xorl %ecx, %ecx | |
| testq %rax, %rax | |
| je .LBB0_3 | |
| .align 16, 0x90 | |
| .LBB0_4: | |
| incq %rcx | |
| cmpq %rcx, %rax | |
| jne .LBB0_4 | |
| movq %rcx, 8(%rsp) | |
| movq %rcx, 8(%rdi) | |
| movq (%rsp), %rax | |
| jmp .LBB0_6 | |
| .LBB0_3: | |
| movq (%rsp), %rax | |
| movq 8(%rsp), %rcx | |
| movq %rcx, 8(%rdi) | |
| .LBB0_6: | |
| movq %rax, (%rdi) | |
| movq %rdi, %rax | |
| addq $16, %rsp | |
| retq | |
| .Ltmp1: | |
| .size _ZN11merge_slice20ha8074868c3655a38MdaE, .Ltmp1-_ZN11merge_slice20ha8074868c3655a38MdaE | |
| .cfi_endproc |
dotdash
commented
Feb 5, 2015
@dotdash could you elaborate on your comment from 4 years ago? (Also related stuff https://gist.github.com/pczarn/62a953ea9ad40d264487 )
@pczarn Sorry, I don't remember what that comment was about. Seems that the IR in my version has the core loop unrolled, but I have no idea whatsoever what caused that difference, i.e. whether I used a different opt-level or modified the compiler or...
@dotdash OK, no worries, I will investigate what causes the difference w.r.t unrolling the core loop, next month.
I will experiment and try to make one-shot hashing and/or adaptive hashing happen.
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