Doc review, as requested :-). #1
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Mostly just phrasing things differently, which is a matter of taste. Feel free to use or not use any of the changes I'm suggesting.
I would say this one thing should be changed, though, not necessarily the way I changed it here.
* Convert any string (literal, `@`, `&`, `~`)
* that contains a base64 encoded value, to the byte values it encodes.
If this structure is going to be used, either the entire clause, 'that contains a base64 encoded value', should be bracketed by commas, or the comma at the end of the clause should be removed.
astrieanna
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Doc review, as requested :-).
astrieanna
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Oct 21, 2013
Passing higher alignment values gives the optimization passes more freedom since it can copy in larger chunks. This change results in rustc outputting the same post-optimization IR as clang for swaps and most copies excluding the lack of information about padding.
Code snippet:
```rust
#[inline(never)]
fn swap<T>(x: &mut T, y: &mut T) {
util::swap(x, y);
}
```
Original IR (for `int`):
```llvm
define internal fastcc void @_ZN9swap_283417_a71830ca3ed2d65d3_00E(i64*, i64*) #1 {
static_allocas:
%2 = icmp eq i64* %0, %1
br i1 %2, label %_ZN4util9swap_283717_a71830ca3ed2d65d3_00E.exit, label %3
; <label>:3 ; preds = %static_allocas
%4 = load i64* %0, align 1
%5 = load i64* %1, align 1
store i64 %5, i64* %0, align 1
store i64 %4, i64* %1, align 1
br label %_ZN4util9swap_283717_a71830ca3ed2d65d3_00E.exit
_ZN4util9swap_283717_a71830ca3ed2d65d3_00E.exit: ; preds = %3, %static_allocas
ret void
}
```
After rust-lang#6710:
```llvm
define internal fastcc void @_ZN9swap_283017_a71830ca3ed2d65d3_00E(i64* nocapture, i64* nocapture) #1 {
static_allocas:
%2 = load i64* %0, align 1
%3 = load i64* %1, align 1
store i64 %3, i64* %0, align 1
store i64 %2, i64* %1, align 1
ret void
}
```
After this change:
```llvm
define internal fastcc void @_ZN9swap_283017_a71830ca3ed2d65d3_00E(i64* nocapture, i64* nocapture) #1 {
static_allocas:
%2 = load i64* %0, align 8
%3 = load i64* %1, align 8
store i64 %3, i64* %0, align 8
store i64 %2, i64* %1, align 8
ret void
}
```
Another example:
```rust
#[inline(never)]
fn set<T>(x: &mut T, y: T) {
*x = y;
}
```
Before, with `(int, int)` (align 1):
```llvm
define internal fastcc void @_ZN8set_282517_8fa972e3f9e451983_00E({ i64, i64 }* nocapture, { i64, i64 }* nocapture) #1 {
static_allocas:
%2 = bitcast { i64, i64 }* %1 to i8*
%3 = bitcast { i64, i64 }* %0 to i8*
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %3, i8* %2, i64 16, i32 1, i1 false)
ret void
}
```
After, with `(int, int)` (align 8):
```llvm
define internal fastcc void @_ZN8set_282617_8fa972e3f9e451983_00E({ i64, i64 }* nocapture, { i64, i64 }* nocapture) #1 {
static_allocas:
%2 = bitcast { i64, i64 }* %1 to i8*
%3 = bitcast { i64, i64 }* %0 to i8*
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %3, i8* %2, i64 16, i32 8, i1 false)
ret void
}
```
astrieanna
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Oct 21, 2013
This allows LLVM to optimize vector iterators to an `getelementptr` and
`icmp` pair, instead of `getelementptr` and *two* comparisons.
Code snippet:
~~~
fn foo(xs: &mut [f64]) {
for x in xs.mut_iter() {
*x += 10.0;
}
}
~~~
LLVM IR at stage0:
~~~
; Function Attrs: noinline uwtable
define void @"_ZN3foo17_68e1b25bca131dba7_0$x2e0E"({ i64, %tydesc*, i8*, i8*, i8 }* nocapture, { double*, i64 }* nocapture) #1 {
"function top level":
%2 = getelementptr inbounds { double*, i64 }* %1, i64 0, i32 0
%3 = load double** %2, align 8
%4 = getelementptr inbounds { double*, i64 }* %1, i64 0, i32 1
%5 = load i64* %4, align 8
%6 = ptrtoint double* %3 to i64
%7 = and i64 %5, -8
%8 = add i64 %7, %6
%9 = inttoptr i64 %8 to double*
%10 = icmp eq double* %3, %9
%11 = icmp eq double* %3, null
%or.cond6 = or i1 %10, %11
br i1 %or.cond6, label %match_case, label %match_else
match_else: ; preds = %"function top level", %match_else
%12 = phi double* [ %13, %match_else ], [ %3, %"function top level" ]
%13 = getelementptr double* %12, i64 1
%14 = load double* %12, align 8
%15 = fadd double %14, 1.000000e+01
store double %15, double* %12, align 8
%16 = icmp eq double* %13, %9
%17 = icmp eq double* %13, null
%or.cond = or i1 %16, %17
br i1 %or.cond, label %match_case, label %match_else
match_case: ; preds = %match_else, %"function top level"
ret void
}
~~~
Optimized LLVM IR at stage1/stage2:
~~~
; Function Attrs: noinline uwtable
define void @"_ZN3foo17_68e1b25bca131dba7_0$x2e0E"({ i64, %tydesc*, i8*, i8*, i8 }* nocapture, { double*, i64 }* nocapture) #1 {
"function top level":
%2 = getelementptr inbounds { double*, i64 }* %1, i64 0, i32 0
%3 = load double** %2, align 8
%4 = getelementptr inbounds { double*, i64 }* %1, i64 0, i32 1
%5 = load i64* %4, align 8
%6 = lshr i64 %5, 3
%7 = getelementptr inbounds double* %3, i64 %6
%8 = icmp eq i64 %6, 0
%9 = icmp eq double* %3, null
%or.cond6 = or i1 %8, %9
br i1 %or.cond6, label %match_case, label %match_else
match_else: ; preds = %"function top level", %match_else
%.sroa.0.0.in7 = phi double* [ %10, %match_else ], [ %3, %"function top level" ]
%10 = getelementptr inbounds double* %.sroa.0.0.in7, i64 1
%11 = load double* %.sroa.0.0.in7, align 8
%12 = fadd double %11, 1.000000e+01
store double %12, double* %.sroa.0.0.in7, align 8
%13 = icmp eq double* %10, %7
br i1 %13, label %match_case, label %match_else
match_case: ; preds = %match_else, %"function top level"
ret void
}
~~~
astrieanna
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that referenced
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Oct 21, 2013
This brings Rust in line with how `clang` handles return pointers.
Example:
pub fn bar() -> [uint, .. 8] {
let a = [0, .. 8];
a
}
Before:
; Function Attrs: nounwind uwtable
define void @_ZN3bar17ha4635c6f704bfa334v0.0E([8 x i64]* nocapture, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #1 {
"function top level":
%a = alloca [8 x i64], align 8
%2 = bitcast [8 x i64]* %a to i8*
call void @llvm.memset.p0i8.i64(i8* %2, i8 0, i64 64, i32 8, i1 false)
%3 = bitcast [8 x i64]* %0 to i8*
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %3, i8* %2, i64 64, i32 8, i1 false)
ret void
}
After:
; Function Attrs: nounwind uwtable
define void @_ZN3bar17ha4635c6f704bfa334v0.0E([8 x i64]* noalias nocapture sret, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #1 {
"function top level":
%2 = bitcast [8 x i64]* %0 to i8*
call void @llvm.memset.p0i8.i64(i8* %2, i8 0, i64 64, i32 8, i1 false)
ret void
}
Closes rust-lang#9072
Closes rust-lang#7298
Closes rust-lang#9154
astrieanna
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Oct 21, 2013
C-like enums are excluded from this for now, because the code paths
specific to them need to be changed.
fn foo() -> Option<~int> { Some(~5) }
Before:
; Function Attrs: uwtable
define void @_ZN3foo18hdec6e36682b87eeaf4v0.0E(%"enum.std::option::Option<~int>[#1]"* noalias nocapture sret, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
"function top level":
%2 = tail call %"enum.std::libc::types::common::c95::c_void[#1]"* @"_ZN2rt11global_heap10malloc_raw17h56c543b77f9b78aY11v0.9$x2dpreE"({ i64, %tydesc*, i8*, i8*, i8 }* undef, i64 8)
%3 = bitcast %"enum.std::libc::types::common::c95::c_void[#1]"* %2 to i64*
store i64 5, i64* %3, align 8
%4 = getelementptr inbounds %"enum.std::option::Option<~int>[#1]"* %0, i64 0, i32 0
store i64* %3, i64** %4, align 8
ret void
}
After:
; Function Attrs: uwtable
define %"enum.std::option::Option<~int>[#1]" @_ZN3foo18h2cbf6557a3143edah4v0.0E({ i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
"function top level":
%1 = tail call %"enum.std::libc::types::common::c95::c_void[#1]"* @"_ZN2rt11global_heap10malloc_raw18hb1e9dd1beab35edau11v0.9$x2dpreE"({ i64, %tydesc*, i8*, i8*, i8 }* undef, i64 8)
%2 = bitcast %"enum.std::libc::types::common::c95::c_void[#1]"* %1 to i64*
store i64 5, i64* %2, align 8
%oldret = insertvalue %"enum.std::option::Option<~int>[#1]" undef, i64* %2, 0
ret %"enum.std::option::Option<~int>[#1]" %oldret
}
astrieanna
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that referenced
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Oct 21, 2013
C-like enums are excluded from this for now, because the code paths
specific to them need to be changed.
fn foo() -> Option<~int> { Some(~5) }
Before:
; Function Attrs: uwtable
define void @_ZN3foo18hdec6e36682b87eeaf4v0.0E(%"enum.std::option::Option<~int>[#1]"* noalias nocapture sret, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
"function top level":
%2 = tail call %"enum.std::libc::types::common::c95::c_void[#1]"* @"_ZN2rt11global_heap10malloc_raw17h56c543b77f9b78aY11v0.9$x2dpreE"({ i64, %tydesc*, i8*, i8*, i8 }* undef, i64 8)
%3 = bitcast %"enum.std::libc::types::common::c95::c_void[#1]"* %2 to i64*
store i64 5, i64* %3, align 8
%4 = getelementptr inbounds %"enum.std::option::Option<~int>[#1]"* %0, i64 0, i32 0
store i64* %3, i64** %4, align 8
ret void
}
After:
; Function Attrs: uwtable
define %"enum.std::option::Option<~int>[#1]" @_ZN3foo18h2cbf6557a3143edah4v0.0E({ i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #0 {
"function top level":
%1 = tail call %"enum.std::libc::types::common::c95::c_void[#1]"* @"_ZN2rt11global_heap10malloc_raw18hb1e9dd1beab35edau11v0.9$x2dpreE"({ i64, %tydesc*, i8*, i8*, i8 }* undef, i64 8)
%2 = bitcast %"enum.std::libc::types::common::c95::c_void[#1]"* %1 to i64*
store i64 5, i64* %2, align 8
%oldret = insertvalue %"enum.std::option::Option<~int>[#1]" undef, i64* %2, 0
ret %"enum.std::option::Option<~int>[#1]" %oldret
}
astrieanna
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Oct 21, 2013
Example:
void ({ i64, %tydesc*, i8*, i8*, i8 }*, i64*, %"struct.std::fmt::Formatter[#1]"*)*
Before, we would print 20 levels deep due to recursion in the type
definition.
astrieanna
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Oct 21, 2013
Example:
void ({ i64, %tydesc*, i8*, i8*, i8 }*, i64*, %"struct.std::fmt::Formatter[#1]"*)*
Before, we would print 20 levels deep due to recursion in the type
definition.
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Mostly just phrasing things differently, which is a matter of taste. Feel free to use or not use any of the changes I'm suggesting.
There's one (very minor) thing that seems like a grammatical error, and not just style issue, though.
Convert any string (literal,@,&,~) that contains a base64 encoded value, to the byte values it encodes.If this structure is going to be used, either the entire clause, 'that contains a base64 encoded value', should be bracketed by commas, or the comma at the end of the clause should be removed.
I think your version, with no edits from me, is still hugely better than the original document, so, whatever :-)
Note: I didn't compile/test this change, because my machine is much, much, slower than yours, so it would take ages, and I'm just editing a few comment strings.