Function parameters that are to be passed by value but don't fit into a
single register are currently passed by creating a copy on the stack and
passing a pointer to that copy to the callee. Since the copy is made
just for the function call, there are no aliases.
For example, this sometimes allows LLVM to eliminate unnecessary calls
to drop glue. Given
````rust
struct Foo {
a: int,
b: Option<~str>,
}
extern {
fn eat(eat: Option<~str>);
}
pub fn foo(v: Foo) {
match v {
Foo { a: _, b } => unsafe { eat(b) }
}
}
````
LLVM currently can't eliminate the drop call for the string, because it
only sees a _pointer_ to Foo, for which it has to expect an alias. So we
get:
````llvm
; Function Attrs: uwtable
define void @_ZN3foo20h9f32c90ae7201edbxaa4v0.0E(%struct.Foo* nocapture) unnamed_addr #0 {
"_ZN34std..option..Option$LT$$UP$str$GT$9glue_drop17hc39b3015f3b9c69dE.exit":
%1 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 1, i32 0
%2 = load { i64, i64, [0 x i8] }** %1, align 8
store { i64, i64, [0 x i8] }* null, { i64, i64, [0 x i8] }** %1, align 8
%3 = ptrtoint { i64, i64, [0 x i8] }* %2 to i64
%.fca.0.insert = insertvalue { i64 } undef, i64 %3, 0
tail call void @eat({ i64 } %.fca.0.insert)
%4 = load { i64, i64, [0 x i8] }** %1, align 8
%5 = icmp eq { i64, i64, [0 x i8] }* %4, null
br i1 %5, label %_ZN3Foo9glue_drop17hf611996539d3036fE.exit, label %"_ZN8_$UP$str9glue_drop17h15dbdbe2b8897a98E.exit.i.i"
"_ZN8_$UP$str9glue_drop17h15dbdbe2b8897a98E.exit.i.i": ; preds = %"_ZN34std..option..Option$LT$$UP$str$GT$9glue_drop17hc39b3015f3b9c69dE.exit"
%6 = bitcast { i64, i64, [0 x i8] }* %4 to i8*
tail call void @free(i8* %6) #1
br label %_ZN3Foo9glue_drop17hf611996539d3036fE.exit
_ZN3Foo9glue_drop17hf611996539d3036fE.exit: ; preds = %"_ZN34std..option..Option$LT$$UP$str$GT$9glue_drop17hc39b3015f3b9c69dE.exit", %"_ZN8_$UP$str9glue_drop17h15dbdbe2b8897a98E.exit.i.i"
ret void
}
````
But with the `noalias` attribute, it can safely optimize that to:
````llvm
define void @_ZN3foo20hd28431f929f0d6c4xaa4v0.0E(%struct.Foo* noalias nocapture) unnamed_addr #0 {
_ZN3Foo9glue_drop17he9afbc09d4e9c851E.exit:
%1 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 1, i32 0
%2 = load { i64, i64, [0 x i8] }** %1, align 8
store { i64, i64, [0 x i8] }* null, { i64, i64, [0 x i8] }** %1, align 8
%3 = ptrtoint { i64, i64, [0 x i8] }* %2 to i64
%.fca.0.insert = insertvalue { i64 } undef, i64 %3, 0
tail call void @eat({ i64 } %.fca.0.insert)
ret void
}
````
Function parameters that are to be passed by value but don't fit into a
single register are currently passed by creating a copy on the stack and
passing a pointer to that copy to the callee. Since the copy is made
just for the function call, there are no aliases.
For example, this sometimes allows LLVM to eliminate unnecessary calls
to drop glue. Given
````rust
struct Foo {
a: int,
b: Option<~str>,
}
extern {
fn eat(eat: Option<~str>);
}
pub fn foo(v: Foo) {
match v {
Foo { a: _, b } => unsafe { eat(b) }
}
}
````
LLVM currently can't eliminate the drop call for the string, because it
only sees a _pointer_ to Foo, for which it has to expect an alias. So we
get:
````llvm
; Function Attrs: uwtable
define void @_ZN3foo20h9f32c90ae7201edbxaa4v0.0E(%struct.Foo* nocapture) unnamed_addr #0 {
"_ZN34std..option..Option$LT$$UP$str$GT$9glue_drop17hc39b3015f3b9c69dE.exit":
%1 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 1, i32 0
%2 = load { i64, i64, [0 x i8] }** %1, align 8
store { i64, i64, [0 x i8] }* null, { i64, i64, [0 x i8] }** %1, align 8
%3 = ptrtoint { i64, i64, [0 x i8] }* %2 to i64
%.fca.0.insert = insertvalue { i64 } undef, i64 %3, 0
tail call void @eat({ i64 } %.fca.0.insert)
%4 = load { i64, i64, [0 x i8] }** %1, align 8
%5 = icmp eq { i64, i64, [0 x i8] }* %4, null
br i1 %5, label %_ZN3Foo9glue_drop17hf611996539d3036fE.exit, label %"_ZN8_$UP$str9glue_drop17h15dbdbe2b8897a98E.exit.i.i"
"_ZN8_$UP$str9glue_drop17h15dbdbe2b8897a98E.exit.i.i": ; preds = %"_ZN34std..option..Option$LT$$UP$str$GT$9glue_drop17hc39b3015f3b9c69dE.exit"
%6 = bitcast { i64, i64, [0 x i8] }* %4 to i8*
tail call void @free(i8* %6) #1
br label %_ZN3Foo9glue_drop17hf611996539d3036fE.exit
_ZN3Foo9glue_drop17hf611996539d3036fE.exit: ; preds = %"_ZN34std..option..Option$LT$$UP$str$GT$9glue_drop17hc39b3015f3b9c69dE.exit", %"_ZN8_$UP$str9glue_drop17h15dbdbe2b8897a98E.exit.i.i"
ret void
}
````
But with the `noalias` attribute, it can safely optimize that to:
````llvm
define void @_ZN3foo20hd28431f929f0d6c4xaa4v0.0E(%struct.Foo* noalias nocapture) unnamed_addr #0 {
_ZN3Foo9glue_drop17he9afbc09d4e9c851E.exit:
%1 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 1, i32 0
%2 = load { i64, i64, [0 x i8] }** %1, align 8
store { i64, i64, [0 x i8] }* null, { i64, i64, [0 x i8] }** %1, align 8
%3 = ptrtoint { i64, i64, [0 x i8] }* %2 to i64
%.fca.0.insert = insertvalue { i64 } undef, i64 %3, 0
tail call void @eat({ i64 } %.fca.0.insert)
ret void
}
````
Change `os::args()` and `os::env()` to use `str::from_utf8_lossy()`.
Add new functions `os::args_as_bytes()` and `os::env_as_bytes()` to retrieve the args/env as byte vectors instead.
The existing methods were left returning strings because I expect that the common use-case is to want string handling.
Fixes#7188.
Parse the environment by default with from_utf8_lossy. Also provide
byte-vector equivalents (e.g. os::env_as_bytes()).
Unfortunately, setenv() can't have a byte-vector equivalent because of
Windows support, unless we want to define a setenv_bytes() that fails
under Windows for non-UTF8 (or non-UTF16).
os::args() was using str::raw::from_c_str(), which would assert if the
C-string wasn't valid UTF-8. Switch to using from_utf8_lossy() instead,
and add a separate function os::args_as_bytes() that returns the ~[u8]
byte-vectors instead.
The std macros used to be injected with a filename of "<std-macros>", but macros
are now injected with a filename of "<{} macros>" where `{}` is filled in with
the crate name. This updates rustdoc to understand this new system so it'll
render source more frequently.
Strip trait impls for types that are stripped either due to the strip-hidden or strip-private passes.
This fixes the search index including trait methods on stripped structs (which breaks searching), and it also removes private types from the implementors list of a trait.
Fixes#9981 and #11439.
The std macros used to be injected with a filename of "<std-macros>", but macros
are now injected with a filename of "<{} macros>" where `{}` is filled in with
the crate name. This updates rustdoc to understand this new system so it'll
render source more frequently.
In strip-private, also strip impls of traits for private types. This
fixes the search index so searching for "drop", "eq", etc doesn't throw
an exception.
This will hopefully bring us closer to #11937. We're still using gcc's idea of
"startup files", but this should prevent us from leaking in dependencies that we
don't quite want (libgcc for example once compiler-rt is what we use).
This will hopefully bring us closer to #11937. We're still using gcc's idea of
"startup files", but this should prevent us from leaking in dependencies that we
don't quite want (libgcc for example once compiler-rt is what we use).
Now that fold_item can return multiple items, this is pretty trivial. It
also recursively expands generated items so ItemDecorators can generate
items that are tagged with ItemDecorators!
Closes#4913
When tests fail, their stdout and stderr is printed as part of the summary, but
this helps suppress failure messages from #[should_fail] tests and generally
clean up the output of the test runner.
Includes an upstream commit by pcwalton to improve codegen of our enums getting
moved around.
This also introduces a new commit on top of our stack of patches to fix a mingw32 build issue. I have submitted the patch upstream: http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20140210/204653.html
I verified that this builds on the try bots, which amazes me because I think that c++11 is turned on now, but I guess we're still lucky!
Closes#10613 (pcwalton's patch landed)
Closes#11992 (llvm has removed these options)
The old method of building up a list of items and threading it through
all of the decorators was unwieldy and not really scalable as
non-deriving ItemDecorators become possible. The API is now that the
decorator gets an immutable reference to the item it's attached to, and
a callback that it can pass new items to. If we want to add syntax
extensions that can modify the item they're attached to, we can add that
later, but I think it'll have to be separate from ItemDecorator to avoid
strange ordering issues.
@huonw
Any single-threaded task benchmark will spend a good chunk of time in `kqueue()` on osx and `epoll()` on linux, and the reason for this is that each time a task is terminated it will hit the syscall. When a task terminates, it context switches back to the scheduler thread, and the scheduler thread falls out of `run_sched_once` whenever it figures out that it did some work.
If we know that `epoll()` will return nothing, then we can continue to do work locally (only while there's work to be done). We must fall back to `epoll()` whenever there's active I/O in order to check whether it's ready or not, but without that (which is largely the case in benchmarks), we can prevent the costly syscall and can get a nice speedup.
I've separated the commits into preparation for this change and then the change itself, the last commit message has more details.
The old method of building up a list of items and threading it through
all of the decorators was unwieldy and not really scalable as
non-deriving ItemDecorators become possible. The API is now that the
decorator gets an immutable reference to the item it's attached to, and
a callback that it can pass new items to. If we want to add syntax
extensions that can modify the item they're attached to, we can add that
later, but I think it'll have to be separate from ItemDecorator to avoid
strange ordering issues.
