Add C API for thread yielding callback.

Sometimes a LLVM compilation may take more time then a client would like to
wait for. The problem is that it is not possible to safely suspend the LLVM
thread from the outside. When the timing is bad it might be possible that the
LLVM thread holds a global mutex and this would block any progress in any other
thread.

This commit adds a new yield callback function that can be registered with a
context. LLVM will try to yield by calling this callback function, but there is
no guaranteed frequency. LLVM will only do so if it can guarantee that
suspending the thread won't block any forward progress in other LLVM contexts
in the same process.

Once the client receives the call back it can suspend the thread safely and
resume it at another time.

Related to <rdar://problem/16728690>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208945 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm-c/Core.h b/include/llvm-c/Core.h
index a86079e0ec002512f8514a1272a6b5db800b12fe..151165e704d752063dfb492c60c068e81fff294b 100644 (file)
--- a/include/llvm-c/Core.h
+++ b/include/llvm-c/Core.h
@@ -467,6 +467,7 @@ void LLVMEnablePrettyStackTrace(void);
  */
 
 typedef void (*LLVMDiagnosticHandler)(LLVMDiagnosticInfoRef, void *);
+typedef void (*LLVMYieldCallback)(LLVMContextRef, void *);
 
 /**
  * Create a new context.
@@ -488,6 +489,14 @@ void LLVMContextSetDiagnosticHandler(LLVMContextRef C,
                                      LLVMDiagnosticHandler Handler,
                                      void *DiagnosticContext);
 
+/**
+ * Set the yield callback function for this context.
+ *
+ * @see LLVMContext::setYieldCallback()
+ */
+void LLVMContextSetYieldCallback(LLVMContextRef C, LLVMYieldCallback Callback,
+                                 void *OpaqueHandle);
+
 /**
  * Destroy a context instance.
  *

diff --git a/include/llvm/IR/LLVMContext.h b/include/llvm/IR/LLVMContext.h
index 7356c17027e4478d3d81078e09a54ab2dd7ca1ce..f9644aca6b47ba3a94d0aa0669c55acb4d616d97 100644 (file)
--- a/include/llvm/IR/LLVMContext.h
+++ b/include/llvm/IR/LLVMContext.h
@@ -72,6 +72,10 @@ public:
   /// \see LLVMContext::diagnose.
   typedef void (*DiagnosticHandlerTy)(const DiagnosticInfo &DI, void *Context);
 
+  /// Defines the type of a yield callback.
+  /// \see LLVMContext::setYieldCallback.
+  typedef void (*YieldCallbackTy)(LLVMContext *Context, void *OpaqueHandle);
+
   /// setInlineAsmDiagnosticHandler - This method sets a handler that is invoked
   /// when problems with inline asm are detected by the backend.  The first
   /// argument is a function pointer and the second is a context pointer that
@@ -118,6 +122,32 @@ public:
   /// for RS_Error, "warning: " for RS_Warning, and "note: " for RS_Note.
   void diagnose(const DiagnosticInfo &DI);
 
+  /// \brief Registers a yield callback with the given context.
+  ///
+  /// The yield callback function may be called by LLVM to transfer control back
+  /// to the client that invoked the LLVM compilation. This can be used to yield
+  /// control of the thread, or perform periodic work needed by the client.
+  /// There is no guaranteed frequency at which callbacks must occur; in fact,
+  /// the client is not guaranteed to ever receive this callback. It is at the
+  /// sole discretion of LLVM to do so and only if it can guarantee that
+  /// suspending the thread won't block any forward progress in other LLVM
+  /// contexts in the same process.
+  ///
+  /// At a suspend point, the state of the current LLVM context is intentionally
+  /// undefined. No assumptions about it can or should be made. Only LLVM
+  /// context API calls that explicitly state that they can be used during a
+  /// yield callback are allowed to be used. Any other API calls into the
+  /// context are not supported until the yield callback function returns
+  /// control to LLVM. Other LLVM contexts are unaffected by this restriction.
+  void setYieldCallback(YieldCallbackTy Callback, void *OpaqueHandle);
+
+  /// \brief Calls the yield callback (if applicable).
+  ///
+  /// This transfers control of the current thread back to the client, which may
+  /// suspend the current thread. Only call this method when LLVM doesn't hold
+  /// any global mutex or cannot block the execution in another LLVM context.
+  void yield();
+
   /// emitError - Emit an error message to the currently installed error handler
   /// with optional location information.  This function returns, so code should
   /// be prepared to drop the erroneous construct on the floor and "not crash".

diff --git a/lib/Analysis/IPA/CallGraphSCCPass.cpp b/lib/Analysis/IPA/CallGraphSCCPass.cpp
index fa9159d13d49deb97612f6212761f8a2203975a9..bfab744d479f857d3ae541b6895c508e221d5645 100644 (file)
--- a/lib/Analysis/IPA/CallGraphSCCPass.cpp
+++ b/lib/Analysis/IPA/CallGraphSCCPass.cpp
@@ -22,6 +22,7 @@
 #include "llvm/IR/Function.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/LegacyPassManagers.h"
+#include "llvm/IR/LLVMContext.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Timer.h"
@@ -145,8 +146,11 @@ bool CGPassManager::RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
        I != E; ++I) {
     if (Function *F = (*I)->getFunction()) {
       dumpPassInfo(P, EXECUTION_MSG, ON_FUNCTION_MSG, F->getName());
-      TimeRegion PassTimer(getPassTimer(FPP));
-      Changed |= FPP->runOnFunction(*F);
+      {
+        TimeRegion PassTimer(getPassTimer(FPP));
+        Changed |= FPP->runOnFunction(*F);
+      }
+      F->getContext().yield();
     }
   }
   

diff --git a/lib/Analysis/LoopPass.cpp b/lib/Analysis/LoopPass.cpp
index 683d6d74ab42949b14ef5bc7c45cf11b408c855a..8df18e75c64e243f619e3a92b0a8cb5c01f6f985 100644 (file)
--- a/lib/Analysis/LoopPass.cpp
+++ b/lib/Analysis/LoopPass.cpp
@@ -15,6 +15,7 @@
 
 #include "llvm/Analysis/LoopPass.h"
 #include "llvm/IR/IRPrintingPasses.h"
+#include "llvm/IR/LLVMContext.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Timer.h"
 using namespace llvm;
@@ -253,6 +254,8 @@ bool LPPassManager::runOnFunction(Function &F) {
 
         // Then call the regular verifyAnalysis functions.
         verifyPreservedAnalysis(P);
+
+        F.getContext().yield();
       }
 
       removeNotPreservedAnalysis(P);

diff --git a/lib/IR/Core.cpp b/lib/IR/Core.cpp
index b1b0abb9efffcfcdca3a8d6f720b52c11946aa6b..81d137edfe05faf63a300f3ce79359496c8fb3ee 100644 (file)
--- a/lib/IR/Core.cpp
+++ b/lib/IR/Core.cpp
@@ -89,6 +89,13 @@ void LLVMContextSetDiagnosticHandler(LLVMContextRef C,
       DiagnosticContext);
 }
 
+void LLVMContextSetYieldCallback(LLVMContextRef C, LLVMYieldCallback Callback,
+                                 void *OpaqueHandle) {
+  auto YieldCallback =
+    LLVM_EXTENSION reinterpret_cast<LLVMContext::YieldCallbackTy>(Callback);
+  unwrap(C)->setYieldCallback(YieldCallback, OpaqueHandle);
+}
+
 void LLVMContextDispose(LLVMContextRef C) {
   delete unwrap(C);
 }

diff --git a/lib/IR/LLVMContext.cpp b/lib/IR/LLVMContext.cpp
index 588e1217bd45b30946898c5b38286f9f053ec55e..5f94dca1eb96d4d213e221f0799aa848bfe80117 100644 (file)
--- a/lib/IR/LLVMContext.cpp
+++ b/lib/IR/LLVMContext.cpp
@@ -115,6 +115,17 @@ void *LLVMContext::getDiagnosticContext() const {
   return pImpl->DiagnosticContext;
 }
 
+void LLVMContext::setYieldCallback(YieldCallbackTy Callback, void *OpaqueHandle)
+{
+  pImpl->YieldCallback = Callback;
+  pImpl->YieldOpaqueHandle = OpaqueHandle;
+}
+
+void LLVMContext::yield() {
+  if (pImpl->YieldCallback)
+    pImpl->YieldCallback(this, pImpl->YieldOpaqueHandle);
+}
+
 void LLVMContext::emitError(const Twine &ErrorStr) {
   diagnose(DiagnosticInfoInlineAsm(ErrorStr));
 }

diff --git a/lib/IR/LLVMContextImpl.cpp b/lib/IR/LLVMContextImpl.cpp
index 78a3c2d304b92a49edae1a6c97a0a4494678a035..2042374647dd1c2cec47339729459bc4ad6a36c4 100644 (file)
--- a/lib/IR/LLVMContextImpl.cpp
+++ b/lib/IR/LLVMContextImpl.cpp
@@ -41,6 +41,8 @@ LLVMContextImpl::LLVMContextImpl(LLVMContext &C)
   InlineAsmDiagContext = nullptr;
   DiagnosticHandler = nullptr;
   DiagnosticContext = nullptr;
+  YieldCallback = nullptr;
+  YieldOpaqueHandle = nullptr;
   NamedStructTypesUniqueID = 0;
 }
 

diff --git a/lib/IR/LLVMContextImpl.h b/lib/IR/LLVMContextImpl.h
index a6a65e6cacd0d34ee351a2917500bea6ad37e61d..b1ad9ff4a5a8a9c9780a94e3c2d15a2d42eb51ea 100644 (file)
--- a/lib/IR/LLVMContextImpl.h
+++ b/lib/IR/LLVMContextImpl.h
@@ -242,6 +242,9 @@ public:
   LLVMContext::DiagnosticHandlerTy DiagnosticHandler;
   void *DiagnosticContext;
 
+  LLVMContext::YieldCallbackTy YieldCallback;
+  void *YieldOpaqueHandle;
+
   typedef DenseMap<DenseMapAPIntKeyInfo::KeyTy, ConstantInt *,
                    DenseMapAPIntKeyInfo> IntMapTy;
   IntMapTy IntConstants;

diff --git a/lib/IR/LegacyPassManager.cpp b/lib/IR/LegacyPassManager.cpp
index b6d75b483f8abc4a0ef33c525a14bff547936581..d3f3482dc02459c8dbeb488c5d09665be46bc81b 100644 (file)
--- a/lib/IR/LegacyPassManager.cpp
+++ b/lib/IR/LegacyPassManager.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 
+#include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/IRPrintingPasses.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/LegacyPassManagers.h"
@@ -1489,8 +1490,10 @@ bool FunctionPassManagerImpl::run(Function &F) {
   TimingInfo::createTheTimeInfo();
 
   initializeAllAnalysisInfo();
-  for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index)
+  for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index) {
     Changed |= getContainedManager(Index)->runOnFunction(F);
+    F.getContext().yield();
+  }
 
   for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index)
     getContainedManager(Index)->cleanup();
@@ -1723,8 +1726,10 @@ bool PassManagerImpl::run(Module &M) {
   }
 
   initializeAllAnalysisInfo();
-  for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index)
+  for (unsigned Index = 0; Index < getNumContainedManagers(); ++Index) {
     Changed |= getContainedManager(Index)->runOnModule(M);
+    M.getContext().yield();
+  }
 
   for (SmallVectorImpl<ImmutablePass *>::const_iterator I = IPV.begin(),
        E = IPV.end(); I != E; ++I) {

diff --git a/lib/IR/PassManager.cpp b/lib/IR/PassManager.cpp
index 3344b09953702e6907dde26dc329436cde964d64..0defb6ab3e42c1bb22efc5ffc84f13494dae7d82 100644 (file)
--- a/lib/IR/PassManager.cpp
+++ b/lib/IR/PassManager.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
@@ -32,6 +33,8 @@ PreservedAnalyses ModulePassManager::run(Module *M, ModuleAnalysisManager *AM) {
     if (AM)
       AM->invalidate(M, PassPA);
     PA.intersect(std::move(PassPA));
+
+    M->getContext().yield();
   }
 
   if (DebugPM)
@@ -92,6 +95,8 @@ PreservedAnalyses FunctionPassManager::run(Function *F,
     if (AM)
       AM->invalidate(F, PassPA);
     PA.intersect(std::move(PassPA));
+
+    F->getContext().yield();
   }
 
   if (DebugPM)

diff --git a/unittests/ExecutionEngine/MCJIT/MCJITCAPITest.cpp b/unittests/ExecutionEngine/MCJIT/MCJITCAPITest.cpp
index 3813d59dbd1195cb0361fe98122cfc68c72a1ce4..20d3f139b4c54f1089f49b30fbc570bd4db2d03b 100644 (file)
--- a/unittests/ExecutionEngine/MCJIT/MCJITCAPITest.cpp
+++ b/unittests/ExecutionEngine/MCJIT/MCJITCAPITest.cpp
@@ -28,6 +28,7 @@ using namespace llvm;
 
 static bool didCallAllocateCodeSection;
 static bool didAllocateCompactUnwindSection;
+static bool didCallYield;
 
 static uint8_t *roundTripAllocateCodeSection(void *object, uintptr_t size,
                                              unsigned alignment,
@@ -64,6 +65,10 @@ static void roundTripDestroy(void *object) {
   delete static_cast<SectionMemoryManager*>(object);
 }
 
+static void yield(LLVMContextRef, void *) {
+  didCallYield = true;
+}
+
 namespace {
 
 // memory manager to test reserve allocation space callback
@@ -142,6 +147,7 @@ protected:
   virtual void SetUp() {
     didCallAllocateCodeSection = false;
     didAllocateCompactUnwindSection = false;
+    didCallYield = false;
     Module = 0;
     Function = 0;
     Engine = 0;
@@ -429,3 +435,24 @@ TEST_F(MCJITCAPITest, reserve_allocation_space) {
   EXPECT_TRUE(MM->UsedCodeSize > 0); 
   EXPECT_TRUE(MM->UsedDataSizeRW > 0);
 }
+
+TEST_F(MCJITCAPITest, yield) {
+  SKIP_UNSUPPORTED_PLATFORM;
+
+  buildSimpleFunction();
+  buildMCJITOptions();
+  buildMCJITEngine();
+  LLVMContextRef C = LLVMGetGlobalContext();
+  LLVMContextSetYieldCallback(C, yield, NULL);
+  buildAndRunPasses();
+
+  union {
+    void *raw;
+    int (*usable)();
+  } functionPointer;
+  functionPointer.raw = LLVMGetPointerToGlobal(Engine, Function);
+
+  EXPECT_EQ(42, functionPointer.usable());
+  EXPECT_TRUE(didCallYield);
+}
+