<div dir="rtl"><div dir="ltr">Hi,</div><div dir="ltr"><br></div><div dir="ltr">Two of the clang test tools, c-arcmt-test and and c-index-test always run the test through one thread only:</div><div dir="ltr"><br></div><div dir="ltr">
<div dir="ltr">/* We intentionally run in a separate thread to ensure we at least minimal</div><div dir="ltr"> * testing of a multithreaded environment (for example, having a reduced stack</div><div dir="ltr"> * size). */</div>
<div><br></div><div>If LLVM/clang were built without thread support, can these tools continue the same?</div><div><br></div><div>Yaron</div><div><br></div></div><div dir="ltr"><br></div></div><div class="gmail_extra"><br>
<br><div class="gmail_quote"><div dir="ltr">2014-06-19 21:18 GMT+03:00 Zachary Turner <span dir="ltr"><<a href="mailto:zturner@google.com" target="_blank">zturner@google.com</a>></span>:</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Author: zturner<br>
Date: Thu Jun 19 13:18:23 2014<br>
New Revision: 211287<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=211287&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=211287&view=rev</a><br>
Log:<br>
Remove support for LLVM runtime multi-threading.<br>
<br>
After a number of previous small iterations, the functions<br>
llvm_start_multithreaded() and llvm_stop_multithreaded() have<br>
been reduced essentially to no-ops. This change removes them<br>
entirely.<br>
<br>
Reviewed by: rnk, dblaikie<br>
<br>
Differential Revision: <a href="http://reviews.llvm.org/D4216" target="_blank">http://reviews.llvm.org/D4216</a><br>
<br>
Modified:<br>
llvm/trunk/docs/ProgrammersManual.rst<br>
llvm/trunk/include/llvm-c/Core.h<br>
llvm/trunk/include/llvm/Support/ManagedStatic.h<br>
llvm/trunk/include/llvm/Support/Threading.h<br>
llvm/trunk/lib/IR/Core.cpp<br>
llvm/trunk/lib/Support/Threading.cpp<br>
llvm/trunk/unittests/Support/ManagedStatic.cpp<br>
<br>
Modified: llvm/trunk/docs/ProgrammersManual.rst<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/ProgrammersManual.rst?rev=211287&r1=211286&r2=211287&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/ProgrammersManual.rst?rev=211287&r1=211286&r2=211287&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/docs/ProgrammersManual.rst (original)<br>
+++ llvm/trunk/docs/ProgrammersManual.rst Thu Jun 19 13:18:23 2014<br>
@@ -2170,46 +2170,13 @@ compiler, consider compiling LLVM and LL<br>
using the resultant compiler to build a copy of LLVM with multithreading<br>
support.<br>
<br>
-.. _startmultithreaded:<br>
-<br>
-Entering and Exiting Multithreaded Mode<br>
----------------------------------------<br>
-<br>
-In order to properly protect its internal data structures while avoiding<br>
-excessive locking overhead in the single-threaded case, the LLVM must intialize<br>
-certain data structures necessary to provide guards around its internals. To do<br>
-so, the client program must invoke ``llvm_start_multithreaded()`` before making<br>
-any concurrent LLVM API calls. To subsequently tear down these structures, use<br>
-the ``llvm_stop_multithreaded()`` call. You can also use the<br>
-``llvm_is_multithreaded()`` call to check the status of multithreaded mode.<br>
-<br>
-Note that both of these calls must be made *in isolation*. That is to say that<br>
-no other LLVM API calls may be executing at any time during the execution of<br>
-``llvm_start_multithreaded()`` or ``llvm_stop_multithreaded``. It is the<br>
-client's responsibility to enforce this isolation.<br>
-<br>
-The return value of ``llvm_start_multithreaded()`` indicates the success or<br>
-failure of the initialization. Failure typically indicates that your copy of<br>
-LLVM was built without multithreading support, typically because GCC atomic<br>
-intrinsics were not found in your system compiler. In this case, the LLVM API<br>
-will not be safe for concurrent calls. However, it *will* be safe for hosting<br>
-threaded applications in the JIT, though :ref:`care must be taken<br>
-<jitthreading>` to ensure that side exits and the like do not accidentally<br>
-result in concurrent LLVM API calls.<br>
-<br>
.. _shutdown:<br>
<br>
Ending Execution with ``llvm_shutdown()``<br>
-----------------------------------------<br>
<br>
When you are done using the LLVM APIs, you should call ``llvm_shutdown()`` to<br>
-deallocate memory used for internal structures. This will also invoke<br>
-``llvm_stop_multithreaded()`` if LLVM is operating in multithreaded mode. As<br>
-such, ``llvm_shutdown()`` requires the same isolation guarantees as<br>
-``llvm_stop_multithreaded()``.<br>
-<br>
-Note that, if you use scope-based shutdown, you can use the<br>
-``llvm_shutdown_obj`` class, which calls ``llvm_shutdown()`` in its destructor.<br>
+deallocate memory used for internal structures.<br>
<br>
.. _managedstatic:<br>
<br>
@@ -2217,15 +2184,11 @@ Lazy Initialization with ``ManagedStatic<br>
------------------------------------------<br>
<br>
``ManagedStatic`` is a utility class in LLVM used to implement static<br>
-initialization of static resources, such as the global type tables. Before the<br>
-invocation of ``llvm_shutdown()``, it implements a simple lazy initialization<br>
-scheme. Once ``llvm_start_multithreaded()`` returns, however, it uses<br>
+initialization of static resources, such as the global type tables. In a<br>
+single-threaded environment, it implements a simple lazy initialization scheme.<br>
+When LLVM is compiled with support for multi-threading, however, it uses<br>
double-checked locking to implement thread-safe lazy initialization.<br>
<br>
-Note that, because no other threads are allowed to issue LLVM API calls before<br>
-``llvm_start_multithreaded()`` returns, it is possible to have<br>
-``ManagedStatic``\ s of ``llvm::sys::Mutex``\ s.<br>
-<br>
.. _llvmcontext:<br>
<br>
Achieving Isolation with ``LLVMContext``<br>
<br>
Modified: llvm/trunk/include/llvm-c/Core.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm-c/Core.h?rev=211287&r1=211286&r2=211287&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm-c/Core.h?rev=211287&r1=211286&r2=211287&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm-c/Core.h (original)<br>
+++ llvm/trunk/include/llvm-c/Core.h Thu Jun 19 13:18:23 2014<br>
@@ -2848,16 +2848,13 @@ void LLVMDisposePassManager(LLVMPassMana<br>
* @{<br>
*/<br>
<br>
-/** Allocate and initialize structures needed to make LLVM safe for<br>
- multithreading. The return value indicates whether multithreaded<br>
- initialization succeeded. Must be executed in isolation from all<br>
- other LLVM api calls.<br>
- @see llvm::llvm_start_multithreaded */<br>
+/** Deprecated: Multi-threading can only be enabled/disabled with the compile<br>
+ time define LLVM_ENABLE_THREADS. This function always returns<br>
+ LLVMIsMultithreaded(). */<br>
LLVMBool LLVMStartMultithreaded(void);<br>
<br>
-/** Deallocate structures necessary to make LLVM safe for multithreading.<br>
- Must be executed in isolation from all other LLVM api calls.<br>
- @see llvm::llvm_stop_multithreaded */<br>
+/** Deprecated: Multi-threading can only be enabled/disabled with the compile<br>
+ time define LLVM_ENABLE_THREADS. */<br>
void LLVMStopMultithreaded(void);<br>
<br>
/** Check whether LLVM is executing in thread-safe mode or not.<br>
<br>
Modified: llvm/trunk/include/llvm/Support/ManagedStatic.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/ManagedStatic.h?rev=211287&r1=211286&r2=211287&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/ManagedStatic.h?rev=211287&r1=211286&r2=211287&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm/Support/ManagedStatic.h (original)<br>
+++ llvm/trunk/include/llvm/Support/ManagedStatic.h Thu Jun 19 13:18:23 2014<br>
@@ -103,9 +103,6 @@ void llvm_shutdown();<br>
/// llvm_shutdown() when it is destroyed.<br>
struct llvm_shutdown_obj {<br>
llvm_shutdown_obj() { }<br>
- explicit llvm_shutdown_obj(bool multithreaded) {<br>
- if (multithreaded) llvm_start_multithreaded();<br>
- }<br>
~llvm_shutdown_obj() { llvm_shutdown(); }<br>
};<br>
<br>
<br>
Modified: llvm/trunk/include/llvm/Support/Threading.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Threading.h?rev=211287&r1=211286&r2=211287&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Threading.h?rev=211287&r1=211286&r2=211287&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/include/llvm/Support/Threading.h (original)<br>
+++ llvm/trunk/include/llvm/Support/Threading.h Thu Jun 19 13:18:23 2014<br>
@@ -7,30 +7,19 @@<br>
//<br>
//===----------------------------------------------------------------------===//<br>
//<br>
-// TThis file defines llvm_start_multithreaded() and friends.<br>
+// This file declares helper functions for running LLVM in a multi-threaded<br>
+// environment.<br>
//<br>
//===----------------------------------------------------------------------===//<br>
<br>
#ifndef LLVM_SUPPORT_THREADING_H<br>
#define LLVM_SUPPORT_THREADING_H<br>
<br>
-namespace llvm {<br>
- /// llvm_start_multithreaded - Allocate and initialize structures needed to<br>
- /// make LLVM safe for multithreading. The return value indicates whether<br>
- /// multithreaded initialization succeeded. LLVM will still be operational<br>
- /// on "failed" return, and will still be safe for hosting threading<br>
- /// applications in the JIT, but will not be safe for concurrent calls to the<br>
- /// LLVM APIs.<br>
- /// THIS MUST EXECUTE IN ISOLATION FROM ALL OTHER LLVM API CALLS.<br>
- bool llvm_start_multithreaded();<br>
-<br>
- /// llvm_stop_multithreaded - Deallocate structures necessary to make LLVM<br>
- /// safe for multithreading.<br>
- /// THIS MUST EXECUTE IN ISOLATION FROM ALL OTHER LLVM API CALLS.<br>
- void llvm_stop_multithreaded();<br>
+#include "llvm/Support/Mutex.h"<br>
<br>
- /// llvm_is_multithreaded - Check whether LLVM is executing in thread-safe<br>
- /// mode or not.<br>
+namespace llvm {<br>
+ /// Returns true if LLVM is compiled with support for multi-threading, and<br>
+ /// false otherwise.<br>
bool llvm_is_multithreaded();<br>
<br>
/// llvm_execute_on_thread - Execute the given \p UserFn on a separate<br>
<br>
Modified: llvm/trunk/lib/IR/Core.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Core.cpp?rev=211287&r1=211286&r2=211287&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Core.cpp?rev=211287&r1=211286&r2=211287&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/IR/Core.cpp (original)<br>
+++ llvm/trunk/lib/IR/Core.cpp Thu Jun 19 13:18:23 2014<br>
@@ -2702,11 +2702,10 @@ void LLVMDisposePassManager(LLVMPassMana<br>
/*===-- Threading ------------------------------------------------------===*/<br>
<br>
LLVMBool LLVMStartMultithreaded() {<br>
- return llvm_start_multithreaded();<br>
+ return LLVMIsMultithreaded();<br>
}<br>
<br>
void LLVMStopMultithreaded() {<br>
- llvm_stop_multithreaded();<br>
}<br>
<br>
LLVMBool LLVMIsMultithreaded() {<br>
<br>
Modified: llvm/trunk/lib/Support/Threading.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Threading.cpp?rev=211287&r1=211286&r2=211287&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Threading.cpp?rev=211287&r1=211286&r2=211287&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/Support/Threading.cpp (original)<br>
+++ llvm/trunk/lib/Support/Threading.cpp Thu Jun 19 13:18:23 2014<br>
@@ -7,7 +7,8 @@<br>
//<br>
//===----------------------------------------------------------------------===//<br>
//<br>
-// This file implements llvm_start_multithreaded() and friends.<br>
+// This file defines helper functions for running LLVM in a multi-threaded<br>
+// environment.<br>
//<br>
//===----------------------------------------------------------------------===//<br>
<br>
@@ -19,38 +20,14 @@<br>
<br>
using namespace llvm;<br>
<br>
-static bool multithreaded_mode = false;<br>
-<br>
-bool llvm::llvm_start_multithreaded() {<br>
+bool llvm::llvm_is_multithreaded() {<br>
#if LLVM_ENABLE_THREADS != 0<br>
- assert(!multithreaded_mode && "Already multithreaded!");<br>
- multithreaded_mode = true;<br>
-<br>
- // We fence here to ensure that all initialization is complete BEFORE we<br>
- // return from llvm_start_multithreaded().<br>
- sys::MemoryFence();<br>
return true;<br>
#else<br>
return false;<br>
#endif<br>
}<br>
<br>
-void llvm::llvm_stop_multithreaded() {<br>
-#if LLVM_ENABLE_THREADS != 0<br>
- assert(multithreaded_mode && "Not currently multithreaded!");<br>
-<br>
- // We fence here to insure that all threaded operations are complete BEFORE we<br>
- // return from llvm_stop_multithreaded().<br>
- sys::MemoryFence();<br>
-<br>
- multithreaded_mode = false;<br>
-#endif<br>
-}<br>
-<br>
-bool llvm::llvm_is_multithreaded() {<br>
- return multithreaded_mode;<br>
-}<br>
-<br>
#if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)<br>
#include <pthread.h><br>
<br>
<br>
Modified: llvm/trunk/unittests/Support/ManagedStatic.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/ManagedStatic.cpp?rev=211287&r1=211286&r2=211287&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/ManagedStatic.cpp?rev=211287&r1=211286&r2=211287&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/unittests/Support/ManagedStatic.cpp (original)<br>
+++ llvm/trunk/unittests/Support/ManagedStatic.cpp Thu Jun 19 13:18:23 2014<br>
@@ -47,7 +47,6 @@ TEST(Initialize, MultipleThreads) {<br>
void *p1 = test1::allocate_stack(a1);<br>
void *p2 = test1::allocate_stack(a2);<br>
<br>
- llvm_start_multithreaded();<br>
pthread_t t1, t2;<br>
pthread_create(&t1, &a1, test1::helper, nullptr);<br>
pthread_create(&t2, &a2, test1::helper, nullptr);<br>
@@ -55,7 +54,6 @@ TEST(Initialize, MultipleThreads) {<br>
pthread_join(t2, nullptr);<br>
free(p1);<br>
free(p2);<br>
- llvm_stop_multithreaded();<br>
}<br>
#endif<br>
<br>
<br>
<br>
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</blockquote></div><br></div>