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Auto merge of #27338 - alexcrichton:remove-morestack, r=brson
This commit removes all morestack support from the compiler which entails: * Segmented stacks are no longer emitted in codegen. * We no longer build or distribute libmorestack.a * The `stack_exhausted` lang item is no longer required The only current use of the segmented stack support in LLVM is to detect stack overflow. This is no longer really required, however, because we already have guard pages for all threads and registered signal handlers watching for a segfault on those pages (to print out a stack overflow message). Additionally, major platforms (aka Windows) already don't use morestack. This means that Rust is by default less likely to catch stack overflows because if a function takes up more than one page of stack space it won't hit the guard page. This is what the purpose of morestack was (to catch this case), but it's better served with stack probes which have more cross platform support and no runtime support necessary. Until LLVM supports this for all platform it looks like morestack isn't really buying us much. cc #16012 (still need stack probes) Closes #26458 (a drive-by fix to help diagnostics on stack overflow) r? @brson
2 parents 75383ea + 7a3fdfb commit 5aca49c

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‎mk/clean.mk

-1
Original file line numberDiff line numberDiff line change
@@ -101,7 +101,6 @@ define CLEAN_TARGET_STAGE_N
101101
clean$(1)_T_$(2)_H_$(3): \
102102
$$(foreach crate,$$(CRATES),clean$(1)_T_$(2)_H_$(3)-lib-$$(crate)) \
103103
$$(foreach tool,$$(TOOLS) $$(DEBUGGER_BIN_SCRIPTS_ALL),clean$(1)_T_$(2)_H_$(3)-tool-$$(tool))
104-
$$(Q)rm -f $$(TLIB$(1)_T_$(2)_H_$(3))/libmorestack.a
105104
$$(Q)rm -f $$(TLIB$(1)_T_$(2)_H_$(3))/libcompiler-rt.a
106105
$(Q)rm -f $$(TLIB$(1)_T_$(2)_H_$(3))/librun_pass_stage* # For unix
107106
$(Q)rm -f $$(TLIB$(1)_T_$(2)_H_$(3))/run_pass_stage* # For windows

‎mk/crates.mk

+1-1
Original file line numberDiff line numberDiff line change
@@ -65,7 +65,7 @@ DEPS_libc := core
6565
DEPS_rustc_unicode := core
6666
DEPS_alloc := core libc native:jemalloc
6767
DEPS_std := core libc rand alloc collections rustc_unicode \
68-
native:rust_builtin native:backtrace native:rustrt_native \
68+
native:rust_builtin native:backtrace \
6969
rustc_bitflags
7070
DEPS_graphviz := std
7171
DEPS_syntax := std term serialize log fmt_macros arena libc

‎mk/main.mk

+6-1
Original file line numberDiff line numberDiff line change
@@ -163,7 +163,7 @@ endif
163163
# that the snapshot will be generated with a statically linked rustc so we only
164164
# have to worry about the distribution of one file (with its native dynamic
165165
# dependencies)
166-
RUSTFLAGS_STAGE0 += -C prefer-dynamic
166+
RUSTFLAGS_STAGE0 += -C prefer-dynamic -C no-stack-check
167167
RUSTFLAGS_STAGE1 += -C prefer-dynamic
168168
RUST_LIB_FLAGS_ST2 += -C prefer-dynamic
169169
RUST_LIB_FLAGS_ST3 += -C prefer-dynamic
@@ -400,6 +400,11 @@ TSREQ$(1)_T_$(2)_H_$(3) = \
400400
$$(foreach obj,$$(INSTALLED_OBJECTS_$(2)),\
401401
$$(TLIB$(1)_T_$(2)_H_$(3))/$$(obj))
402402

403+
ifeq ($(1),0)
404+
TSREQ$(1)_T_$(2)_H_$(3) += \
405+
$$(TLIB$(1)_T_$(2)_H_$(3))/$$(call CFG_STATIC_LIB_NAME_$(2),morestack)
406+
endif
407+
403408
# Prerequisites for a working stageN compiler and libraries, for a specific
404409
# target
405410
SREQ$(1)_T_$(2)_H_$(3) = \

‎mk/platform.mk

+1-2
Original file line numberDiff line numberDiff line change
@@ -113,8 +113,7 @@ CFG_RLIB_GLOB=lib$(1)-*.rlib
113113
include $(wildcard $(CFG_SRC_DIR)mk/cfg/*.mk)
114114

115115
define ADD_INSTALLED_OBJECTS
116-
INSTALLED_OBJECTS_$(1) += $$(call CFG_STATIC_LIB_NAME_$(1),morestack) \
117-
$$(call CFG_STATIC_LIB_NAME_$(1),compiler-rt)
116+
INSTALLED_OBJECTS_$(1) += $$(call CFG_STATIC_LIB_NAME_$(1),compiler-rt)
118117
endef
119118

120119
$(foreach target,$(CFG_TARGET), \

‎mk/rt.mk

+3-5
Original file line numberDiff line numberDiff line change
@@ -35,8 +35,8 @@
3535
# that's per-target so you're allowed to conditionally add files based on the
3636
# target.
3737
################################################################################
38-
NATIVE_LIBS := rust_builtin hoedown morestack miniz \
39-
rustrt_native rust_test_helpers
38+
NATIVE_LIBS := rust_builtin hoedown miniz \
39+
rust_test_helpers morestack
4040

4141
# $(1) is the target triple
4242
define NATIVE_LIBRARIES
@@ -53,10 +53,8 @@ NATIVE_DEPS_hoedown_$(1) := hoedown/src/autolink.c \
5353
NATIVE_DEPS_miniz_$(1) = miniz.c
5454
NATIVE_DEPS_rust_builtin_$(1) := rust_builtin.c \
5555
rust_android_dummy.c
56-
NATIVE_DEPS_rustrt_native_$(1) := arch/$$(HOST_$(1))/record_sp.S
5756
NATIVE_DEPS_rust_test_helpers_$(1) := rust_test_helpers.c
58-
NATIVE_DEPS_morestack_$(1) := arch/$$(HOST_$(1))/morestack.S
59-
57+
NATIVE_DEPS_morestack_$(1) := empty.c
6058

6159
################################################################################
6260
# You shouldn't find it that necessary to edit anything below this line.

‎mk/target.mk

+1-2
Original file line numberDiff line numberDiff line change
@@ -56,8 +56,7 @@ $(foreach host,$(CFG_HOST), \
5656
# 1. The immediate dependencies are the rust source files
5757
# 2. Each rust crate dependency is listed (based on their stamp files),
5858
# as well as all native dependencies (listed in RT_OUTPUT_DIR)
59-
# 3. The stage (n-1) compiler is required through the TSREQ dependency, along
60-
# with the morestack library
59+
# 3. The stage (n-1) compiler is required through the TSREQ dependency
6160
# 4. When actually executing the rule, the first thing we do is to clean out
6261
# old libs and rlibs via the REMOVE_ALL_OLD_GLOB_MATCHES macro
6362
# 5. Finally, we get around to building the actual crate. It's just one

‎src/doc/trpl/lang-items.md

-1
Original file line numberDiff line numberDiff line change
@@ -51,7 +51,6 @@ fn main(argc: isize, argv: *const *const u8) -> isize {
5151
0
5252
}
5353

54-
#[lang = "stack_exhausted"] extern fn stack_exhausted() {}
5554
#[lang = "eh_personality"] extern fn eh_personality() {}
5655
#[lang = "panic_fmt"] fn panic_fmt() -> ! { loop {} }
5756
# #[lang = "eh_unwind_resume"] extern fn rust_eh_unwind_resume() {}

‎src/doc/trpl/no-stdlib.md

+2-11
Original file line numberDiff line numberDiff line change
@@ -36,7 +36,6 @@ fn start(_argc: isize, _argv: *const *const u8) -> isize {
3636
// These functions and traits are used by the compiler, but not
3737
// for a bare-bones hello world. These are normally
3838
// provided by libstd.
39-
#[lang = "stack_exhausted"] extern fn stack_exhausted() {}
4039
#[lang = "eh_personality"] extern fn eh_personality() {}
4140
#[lang = "panic_fmt"] fn panic_fmt() -> ! { loop {} }
4241
# #[lang = "eh_unwind_resume"] extern fn rust_eh_unwind_resume() {}
@@ -61,7 +60,6 @@ pub extern fn main(argc: i32, argv: *const *const u8) -> i32 {
6160
0
6261
}
6362
64-
#[lang = "stack_exhausted"] extern fn stack_exhausted() {}
6563
#[lang = "eh_personality"] extern fn eh_personality() {}
6664
#[lang = "panic_fmt"] fn panic_fmt() -> ! { loop {} }
6765
# #[lang = "eh_unwind_resume"] extern fn rust_eh_unwind_resume() {}
@@ -73,18 +71,12 @@ The compiler currently makes a few assumptions about symbols which are available
7371
in the executable to call. Normally these functions are provided by the standard
7472
library, but without it you must define your own.
7573

76-
The first of these three functions, `stack_exhausted`, is invoked whenever stack
77-
overflow is detected. This function has a number of restrictions about how it
78-
can be called and what it must do, but if the stack limit register is not being
79-
maintained then a thread always has an "infinite stack" and this function
80-
shouldn't get triggered.
81-
82-
The second of these three functions, `eh_personality`, is used by the
74+
The first of these two functions, `eh_personality`, is used by the
8375
failure mechanisms of the compiler. This is often mapped to GCC's
8476
personality function (see the
8577
[libstd implementation](../std/rt/unwind/index.html) for more
8678
information), but crates which do not trigger a panic can be assured
87-
that this function is never called. The final function, `panic_fmt`, is
79+
that this function is never called. The second function, `panic_fmt`, is
8880
also used by the failure mechanisms of the compiler.
8981

9082
## Using libcore
@@ -150,7 +142,6 @@ extern fn panic_fmt(args: &core::fmt::Arguments,
150142
loop {}
151143
}
152144
153-
#[lang = "stack_exhausted"] extern fn stack_exhausted() {}
154145
#[lang = "eh_personality"] extern fn eh_personality() {}
155146
# #[lang = "eh_unwind_resume"] extern fn rust_eh_unwind_resume() {}
156147
# #[start] fn start(argc: isize, argv: *const *const u8) -> isize { 0 }

‎src/librustc/middle/lang_items.rs

-2
Original file line numberDiff line numberDiff line change
@@ -347,7 +347,5 @@ lets_do_this! {
347347

348348
NonZeroItem, "non_zero", non_zero;
349349

350-
StackExhaustedLangItem, "stack_exhausted", stack_exhausted;
351-
352350
DebugTraitLangItem, "debug_trait", debug_trait;
353351
}

‎src/librustc/middle/weak_lang_items.rs

-4
Original file line numberDiff line numberDiff line change
@@ -39,9 +39,6 @@ pub fn check_crate(krate: &ast::Crate,
3939
// These are never called by user code, they're generated by the compiler.
4040
// They will never implicitly be added to the `missing` array unless we do
4141
// so here.
42-
if items.stack_exhausted().is_none() {
43-
items.missing.push(lang_items::StackExhaustedLangItem);
44-
}
4542
if items.eh_personality().is_none() {
4643
items.missing.push(lang_items::EhPersonalityLangItem);
4744
}
@@ -124,7 +121,6 @@ impl<'a, 'v> Visitor<'v> for Context<'a> {
124121

125122
weak_lang_items! {
126123
panic_fmt, PanicFmtLangItem, rust_begin_unwind;
127-
stack_exhausted, StackExhaustedLangItem, rust_stack_exhausted;
128124
eh_personality, EhPersonalityLangItem, rust_eh_personality;
129125
eh_unwind_resume, EhUnwindResumeLangItem, rust_eh_unwind_resume;
130126
}

‎src/librustc_back/target/apple_base.rs

-1
Original file line numberDiff line numberDiff line change
@@ -19,7 +19,6 @@ pub fn opts() -> TargetOptions {
1919
dynamic_linking: true,
2020
executables: true,
2121
is_like_osx: true,
22-
morestack: true,
2322
has_rpath: true,
2423
dll_prefix: "lib".to_string(),
2524
dll_suffix: ".dylib".to_string(),

‎src/librustc_back/target/apple_ios_base.rs

-8
Original file line numberDiff line numberDiff line change
@@ -87,14 +87,6 @@ pub fn opts(arch: Arch) -> TargetOptions {
8787
cpu: target_cpu(arch),
8888
dynamic_linking: false,
8989
executables: true,
90-
// Although there is an experimental implementation of LLVM which
91-
// supports SS on armv7 it wasn't approved by Apple, see:
92-
// http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20140505/216350.html
93-
// It looks like it might be never accepted to upstream LLVM.
94-
//
95-
// SS might be also enabled on Arm64 as it has builtin support in LLVM
96-
// but I haven't tested it through yet
97-
morestack: false,
9890
pre_link_args: pre_link_args(arch),
9991
.. super::apple_base::opts()
10092
}

‎src/librustc_back/target/bitrig_base.rs

-1
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,6 @@ pub fn opts() -> TargetOptions {
1616
linker: "cc".to_string(),
1717
dynamic_linking: true,
1818
executables: true,
19-
morestack: false,
2019
linker_is_gnu: true,
2120
has_rpath: true,
2221
position_independent_executables: true,

‎src/librustc_back/target/dragonfly_base.rs

-1
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,6 @@ pub fn opts() -> TargetOptions {
1616
linker: "cc".to_string(),
1717
dynamic_linking: true,
1818
executables: true,
19-
morestack: true,
2019
linker_is_gnu: true,
2120
has_rpath: true,
2221
pre_link_args: vec!(

‎src/librustc_back/target/freebsd_base.rs

-1
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,6 @@ pub fn opts() -> TargetOptions {
1616
linker: "cc".to_string(),
1717
dynamic_linking: true,
1818
executables: true,
19-
morestack: true,
2019
has_rpath: true,
2120
archive_format: "gnu".to_string(),
2221

‎src/librustc_back/target/i686_unknown_freebsd.rs

-1
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,6 @@ pub fn target() -> Target {
1414
let mut base = super::freebsd_base::opts();
1515
base.cpu = "pentium4".to_string();
1616
base.pre_link_args.push("-m32".to_string());
17-
base.morestack = false;
1817

1918
Target {
2019
llvm_target: "i686-unknown-freebsd".to_string(),

‎src/librustc_back/target/linux_base.rs

-1
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,6 @@ pub fn opts() -> TargetOptions {
1515
TargetOptions {
1616
dynamic_linking: true,
1717
executables: true,
18-
morestack: true,
1918
linker_is_gnu: true,
2019
has_rpath: true,
2120
pre_link_args: vec![

‎src/librustc_back/target/mod.rs

-5
Original file line numberDiff line numberDiff line change
@@ -118,9 +118,6 @@ pub struct TargetOptions {
118118
/// Whether executables are available on this target. iOS, for example, only allows static
119119
/// libraries. Defaults to false.
120120
pub executables: bool,
121-
/// Whether LLVM's segmented stack prelude is supported by whatever runtime is available.
122-
/// Will emit stack checks and calls to __morestack. Defaults to false.
123-
pub morestack: bool,
124121
/// Relocation model to use in object file. Corresponds to `llc
125122
/// -relocation-model=$relocation_model`. Defaults to "pic".
126123
pub relocation_model: String,
@@ -192,7 +189,6 @@ impl Default for TargetOptions {
192189
features: "".to_string(),
193190
dynamic_linking: false,
194191
executables: false,
195-
morestack: false,
196192
relocation_model: "pic".to_string(),
197193
code_model: "default".to_string(),
198194
disable_redzone: false,
@@ -298,7 +294,6 @@ impl Target {
298294
key!(data_layout);
299295
key!(dynamic_linking, bool);
300296
key!(executables, bool);
301-
key!(morestack, bool);
302297
key!(disable_redzone, bool);
303298
key!(eliminate_frame_pointer, bool);
304299
key!(function_sections, bool);

‎src/librustc_back/target/netbsd_base.rs

-1
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,6 @@ pub fn opts() -> TargetOptions {
1616
linker: "cc".to_string(),
1717
dynamic_linking: true,
1818
executables: true,
19-
morestack: false,
2019
linker_is_gnu: true,
2120
has_rpath: true,
2221
pre_link_args: vec!(

‎src/librustc_back/target/openbsd_base.rs

-1
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,6 @@ pub fn opts() -> TargetOptions {
1616
linker: "cc".to_string(),
1717
dynamic_linking: true,
1818
executables: true,
19-
morestack: false,
2019
linker_is_gnu: true,
2120
has_rpath: true,
2221
pre_link_args: vec!(

‎src/librustc_back/target/windows_base.rs

-1
Original file line numberDiff line numberDiff line change
@@ -23,7 +23,6 @@ pub fn opts() -> TargetOptions {
2323
exe_suffix: ".exe".to_string(),
2424
staticlib_prefix: "".to_string(),
2525
staticlib_suffix: ".lib".to_string(),
26-
morestack: false,
2726
is_like_windows: true,
2827
archive_format: "gnu".to_string(),
2928
pre_link_args: vec!(

‎src/librustc_back/target/windows_msvc_base.rs

-1
Original file line numberDiff line numberDiff line change
@@ -53,7 +53,6 @@ pub fn opts() -> TargetOptions {
5353
exe_suffix: ".exe".to_string(),
5454
staticlib_prefix: "".to_string(),
5555
staticlib_suffix: ".lib".to_string(),
56-
morestack: false,
5756
is_like_windows: true,
5857
is_like_msvc: true,
5958
pre_link_args: vec![

‎src/librustc_trans/back/link.rs

-23
Original file line numberDiff line numberDiff line change
@@ -759,9 +759,6 @@ fn link_staticlib(sess: &Session, objects: &[PathBuf], out_filename: &Path,
759759
if sess.target.target.options.is_like_osx && !ab.using_llvm() {
760760
ab.build();
761761
}
762-
if sess.target.target.options.morestack {
763-
ab.add_native_library("morestack").unwrap();
764-
}
765762
if !sess.target.target.options.no_compiler_rt {
766763
ab.add_native_library("compiler-rt").unwrap();
767764
}
@@ -905,26 +902,6 @@ fn link_args(cmd: &mut Linker,
905902
}
906903
cmd.output_filename(out_filename);
907904

908-
// Stack growth requires statically linking a __morestack function. Note
909-
// that this is listed *before* all other libraries. Due to the usage of the
910-
// --as-needed flag below, the standard library may only be useful for its
911-
// rust_stack_exhausted function. In this case, we must ensure that the
912-
// libmorestack.a file appears *before* the standard library (so we put it
913-
// at the very front).
914-
//
915-
// Most of the time this is sufficient, except for when LLVM gets super
916-
// clever. If, for example, we have a main function `fn main() {}`, LLVM
917-
// will optimize out calls to `__morestack` entirely because the function
918-
// doesn't need any stack at all!
919-
//
920-
// To get around this snag, we specially tell the linker to always include
921-
// all contents of this library. This way we're guaranteed that the linker
922-
// will include the __morestack symbol 100% of the time, always resolving
923-
// references to it even if the object above didn't use it.
924-
if t.options.morestack {
925-
cmd.link_whole_staticlib("morestack", &[lib_path]);
926-
}
927-
928905
// When linking a dynamic library, we put the metadata into a section of the
929906
// executable. This metadata is in a separate object file from the main
930907
// object file, so we link that in here.

‎src/librustc_trans/trans/attributes.rs

+1-16
Original file line numberDiff line numberDiff line change
@@ -23,19 +23,6 @@ use trans::context::CrateContext;
2323
use trans::machine;
2424
use trans::type_of;
2525

26-
/// Mark LLVM function to use split stack.
27-
#[inline]
28-
pub fn split_stack(val: ValueRef, set: bool) {
29-
unsafe {
30-
let attr = "split-stack\0".as_ptr() as *const _;
31-
if set {
32-
llvm::LLVMAddFunctionAttrString(val, llvm::FunctionIndex as c_uint, attr);
33-
} else {
34-
llvm::LLVMRemoveFunctionAttrString(val, llvm::FunctionIndex as c_uint, attr);
35-
}
36-
}
37-
}
38-
3926
/// Mark LLVM function to use provided inline heuristic.
4027
#[inline]
4128
pub fn inline(val: ValueRef, inline: InlineAttr) {
@@ -123,9 +110,7 @@ pub fn from_fn_attrs(ccx: &CrateContext, attrs: &[ast::Attribute], llfn: ValueRe
123110
}
124111

125112
for attr in attrs {
126-
if attr.check_name("no_stack_check") {
127-
split_stack(llfn, false);
128-
} else if attr.check_name("cold") {
113+
if attr.check_name("cold") {
129114
unsafe {
130115
llvm::LLVMAddFunctionAttribute(llfn,
131116
llvm::FunctionIndex as c_uint,

‎src/librustc_trans/trans/base.rs

+2-16
Original file line numberDiff line numberDiff line change
@@ -2166,17 +2166,8 @@ fn finish_register_fn(ccx: &CrateContext, sym: String, node_id: ast::NodeId,
21662166
llfn: ValueRef) {
21672167
ccx.item_symbols().borrow_mut().insert(node_id, sym);
21682168

2169-
// The stack exhaustion lang item shouldn't have a split stack because
2170-
// otherwise it would continue to be exhausted (bad), and both it and the
2171-
// eh_personality functions need to be externally linkable.
2169+
// The eh_personality function need to be externally linkable.
21722170
let def = ast_util::local_def(node_id);
2173-
if ccx.tcx().lang_items.stack_exhausted() == Some(def) {
2174-
attributes::split_stack(llfn, false);
2175-
llvm::SetLinkage(llfn, llvm::ExternalLinkage);
2176-
if ccx.use_dll_storage_attrs() {
2177-
llvm::SetDLLStorageClass(llfn, llvm::DLLExportStorageClass);
2178-
}
2179-
}
21802171
if ccx.tcx().lang_items.eh_personality() == Some(def) {
21812172
llvm::SetLinkage(llfn, llvm::ExternalLinkage);
21822173
if ccx.use_dll_storage_attrs() {
@@ -2794,13 +2785,8 @@ pub fn trans_crate(tcx: &ty::ctxt, analysis: ty::CrateAnalysis) -> CrateTranslat
27942785
});
27952786

27962787
// Make sure that some other crucial symbols are not eliminated from the
2797-
// module. This includes the main function, the crate map (used for debug
2798-
// log settings and I/O), and finally the curious rust_stack_exhausted
2799-
// symbol. This symbol is required for use by the libmorestack library that
2800-
// we link in, so we must ensure that this symbol is not internalized (if
2801-
// defined in the crate).
2788+
// module, including the main function.
28022789
reachable.push("main".to_string());
2803-
reachable.push("rust_stack_exhausted".to_string());
28042790

28052791
// referenced from .eh_frame section on some platforms
28062792
reachable.push("rust_eh_personality".to_string());

‎src/librustc_trans/trans/context.rs

-5
Original file line numberDiff line numberDiff line change
@@ -570,11 +570,6 @@ impl<'b, 'tcx> CrateContext<'b, 'tcx> {
570570
}
571571
}
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573-
pub fn is_split_stack_supported(&self) -> bool {
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self.sess().target.target.options.morestack
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}
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pub fn llmod(&self) -> ModuleRef {
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self.local.llmod
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}

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