Merge rust-lang#15

15: Move most of the control point logic into to Rust code. r=ltratt a=vext01



Co-authored-by: Edd Barrett <vext01@gmail.com>

Author: bors[bot]

llvm/lib/Transforms/Yk/ControlPoint.cpp

@@ -88,6 +88,11 @@
 #define DEBUG_TYPE "yk-control-point"
 #define JIT_STATE_PREFIX "jit-state: "
 
+// These constants mirror `ykrt::mt::JITACTION_*`.
+const uintptr_t JITActionNop = 1;
+const uintptr_t JITActionStartTracing = 2;
+const uintptr_t JITActionStopTracing = 3;
+
 using namespace llvm;
 
 /// Find the call to the dummy control point that we want to patch.
@@ -130,20 +135,34 @@ void createControlPoint(Module &Mod, Function *F, std::vector<Value *> LiveVars,
 
   // Create control point blocks and setup the IRBuilder.
   BasicBlock *CtrlPointEntry = BasicBlock::Create(Context, "cpentry", F);
-  BasicBlock *BBTracing = BasicBlock::Create(Context, "bbtracing", F);
-  BasicBlock *BBNotTracing = BasicBlock::Create(Context, "bbnottracing", F);
-  BasicBlock *BBHasTrace = BasicBlock::Create(Context, "bbhastrace", F);
-  BasicBlock *BBExecuteTrace = BasicBlock::Create(Context, "bbhastrace", F);
-  BasicBlock *BBHasNoTrace = BasicBlock::Create(Context, "bbhasnotrace", F);
+  BasicBlock *BBExecuteTrace = BasicBlock::Create(Context, "bbhexectrace", F);
+  BasicBlock *BBStartTracing = BasicBlock::Create(Context, "bbstarttracing", F);
   BasicBlock *BBReturn = BasicBlock::Create(Context, "bbreturn", F);
   BasicBlock *BBStopTracing = BasicBlock::Create(Context, "bbstoptracing", F);
-  IRBuilder<> Builder(CtrlPointEntry);
+
+  // Get the type for a pointer-sized integer.
+  DataLayout DL(&Mod);
+  unsigned PtrBitSize = DL.getPointerSize() * 8;
+  IntegerType *PtrSizedInteger = IntegerType::getIntNTy(Context, PtrBitSize);
 
   // Some frequently used constants.
-  ConstantInt *Int0 = ConstantInt::get(Context, APInt(8, 0));
-  Constant *PtNull = Constant::getNullValue(Type::getInt8PtrTy(Context));
+  ConstantInt *JActNop = ConstantInt::get(PtrSizedInteger, JITActionNop);
+  ConstantInt *JActStartTracing =
+      ConstantInt::get(PtrSizedInteger, JITActionStartTracing);
+  ConstantInt *JActStopTracing =
+      ConstantInt::get(PtrSizedInteger, JITActionStopTracing);
+
+  // Add definitions for __yk functions.
+  Function *FuncTransLoc = llvm::Function::Create(
+      FunctionType::get(PtrSizedInteger, {Type::getInt8PtrTy(Context)}, false),
+      GlobalValue::ExternalLinkage, "__ykrt_transition_location", Mod);
+
+  Function *FuncSetCodePtr = llvm::Function::Create(
+      FunctionType::get(
+          Type::getVoidTy(Context),
+          {Type::getInt8PtrTy(Context), Type::getInt8PtrTy(Context)}, false),
+      GlobalValue::ExternalLinkage, "__ykrt_set_loc_code_ptr", Mod);
 
-  // Add definitions for __yktrace functions.
   Function *FuncStartTracing = llvm::Function::Create(
       FunctionType::get(Type::getVoidTy(Context), {Type::getInt64Ty(Context)},
                         false),
@@ -158,82 +177,52 @@ void createControlPoint(Module &Mod, Function *F, std::vector<Value *> LiveVars,
                         {Type::getInt8PtrTy(Context)}, false),
       GlobalValue::ExternalLinkage, "__yktrace_irtrace_compile", Mod);
 
-  // Generate global variables to hold the state of the JIT.
-  GlobalVariable *GVTracing = new GlobalVariable(
-      Mod, Type::getInt8Ty(Context), false, GlobalVariable::InternalLinkage,
-      Int0, "tracing", (GlobalVariable *)nullptr);
-
-  GlobalVariable *GVCompiledTrace = new GlobalVariable(
-      Mod, Type::getInt8PtrTy(Context), false, GlobalVariable::InternalLinkage,
-      PtNull, "compiled_trace", (GlobalVariable *)nullptr);
-
-  GlobalVariable *GVStartLoc = new GlobalVariable(
-      Mod, YkLocTy, false, GlobalVariable::InternalLinkage,
-      Constant::getNullValue(YkLocTy), "start_loc", (GlobalVariable *)nullptr);
-
-  // Create control point entry block. Checks if we are currently tracing.
-  Value *GVTracingVal = Builder.CreateLoad(Type::getInt8Ty(Context), GVTracing);
-  Value *IsTracing =
-      Builder.CreateICmp(CmpInst::Predicate::ICMP_EQ, GVTracingVal, Int0);
-  Builder.CreateCondBr(IsTracing, BBNotTracing, BBTracing);
-
-  // Create block for "not tracing" case. Checks if we already compiled a trace.
-  Builder.SetInsertPoint(BBNotTracing);
-  Value *GVCompiledTraceVal =
-      Builder.CreateLoad(Type::getInt8PtrTy(Context), GVCompiledTrace);
-  Value *HasTrace = Builder.CreateICmp(CmpInst::Predicate::ICMP_EQ,
-                                       GVCompiledTraceVal, PtNull);
-  Builder.CreateCondBr(HasTrace, BBHasNoTrace, BBHasTrace);
-
-  // Create block that starts tracing.
-  Builder.SetInsertPoint(BBHasNoTrace);
+  // Populate the entry block. This calls `__ykrt_transition_location()` to
+  // decide what to do next.
+  IRBuilder<> Builder(CtrlPointEntry);
+  Value *CastLoc =
+      Builder.CreateBitCast(F->getArg(0), Type::getInt8PtrTy(Context));
+  Value *JITAction = Builder.CreateCall(FuncTransLoc->getFunctionType(),
+                                        FuncTransLoc, {CastLoc});
+  SwitchInst *ActionSw = Builder.CreateSwitch(JITAction, BBExecuteTrace, 3);
+  ActionSw->addCase(JActNop, BBReturn);
+  ActionSw->addCase(JActStartTracing, BBStartTracing);
+  ActionSw->addCase(JActStopTracing, BBStopTracing);
+
+  // Populate the block that starts tracing.
+  Builder.SetInsertPoint(BBStartTracing);
   createJITStatePrint(Builder, &Mod, "start-tracing");
   Builder.CreateCall(FuncStartTracing->getFunctionType(), FuncStartTracing,
                      {ConstantInt::get(Context, APInt(64, 1))});
-  Builder.CreateStore(ConstantInt::get(Context, APInt(8, 1)), GVTracing);
-  Builder.CreateStore(F->getArg(0), GVStartLoc);
   Builder.CreateBr(BBReturn);
 
-  // Create block that checks if we've reached the same location again so we
-  // can execute a compiled trace.
-  Builder.SetInsertPoint(BBHasTrace);
-  Value *ValStartLoc = Builder.CreateLoad(YkLocTy, GVStartLoc);
-  Value *ExecTraceCond = Builder.CreateICmp(CmpInst::Predicate::ICMP_EQ,
-                                            ValStartLoc, F->getArg(0));
-  Builder.CreateCondBr(ExecTraceCond, BBExecuteTrace, BBReturn);
-
-  // Create block that executes a compiled trace.
+  // Populate the block that calls a compiled trace. If execution gets into
+  // this block then `JITAction` is a pointer to a compiled trace.
   Builder.SetInsertPoint(BBExecuteTrace);
   std::vector<Type *> TypeParams;
   for (Value *LV : LiveVars) {
     TypeParams.push_back(LV->getType());
   }
   FunctionType *FType =
       FunctionType::get(YkCtrlPointStruct, {YkCtrlPointStruct}, false);
-  Value *CastTrace =
-      Builder.CreateBitCast(GVCompiledTraceVal, FType->getPointerTo());
+  Value *JITActionPtr =
+      Builder.CreateIntToPtr(JITAction, Type::getInt8PtrTy(Context));
+  Value *CastTrace = Builder.CreateBitCast(JITActionPtr, FType->getPointerTo());
   createJITStatePrint(Builder, &Mod, "enter-jit-code");
   CallInst *CTResult = Builder.CreateCall(FType, CastTrace, F->getArg(1));
   createJITStatePrint(Builder, &Mod, "exit-jit-code");
   CTResult->setTailCall(true);
   Builder.CreateBr(BBExecuteTrace);
 
-  // Create block that decides when to stop tracing.
-  Builder.SetInsertPoint(BBTracing);
-  Value *ValStartLoc2 = Builder.CreateLoad(YkLocTy, GVStartLoc);
-  Value *StopTracingCond = Builder.CreateICmp(CmpInst::Predicate::ICMP_EQ,
-                                              ValStartLoc2, F->getArg(0));
-  Builder.CreateCondBr(StopTracingCond, BBStopTracing, BBReturn);
-
   // Create block that stops tracing, compiles a trace, and stores it in a
   // global variable.
   Builder.SetInsertPoint(BBStopTracing);
   Value *TR =
       Builder.CreateCall(FuncStopTracing->getFunctionType(), FuncStopTracing);
   Value *CT = Builder.CreateCall(FuncCompileTrace->getFunctionType(),
                                  FuncCompileTrace, {TR});
-  Builder.CreateStore(CT, GVCompiledTrace);
-  Builder.CreateStore(ConstantInt::get(Context, APInt(8, 0)), GVTracing);
+  Builder.CreateCall(FuncSetCodePtr->getFunctionType(), FuncSetCodePtr,
+                     {CastLoc, CT});
   createJITStatePrint(Builder, &Mod, "stop-tracing");
   Builder.CreateBr(BBReturn);
 
@@ -242,10 +231,9 @@ void createControlPoint(Module &Mod, Function *F, std::vector<Value *> LiveVars,
   // which contains the changed interpreter state.
   Builder.SetInsertPoint(BBReturn);
   Value *YkCtrlPointVars = F->getArg(1);
-  PHINode *Phi = Builder.CreatePHI(YkCtrlPointStruct, 3);
-  Phi->addIncoming(YkCtrlPointVars, BBHasTrace);
-  Phi->addIncoming(YkCtrlPointVars, BBTracing);
-  Phi->addIncoming(YkCtrlPointVars, BBHasNoTrace);
+  PHINode *Phi = Builder.CreatePHI(YkCtrlPointStruct, 2);
+  Phi->addIncoming(YkCtrlPointVars, CtrlPointEntry);
+  Phi->addIncoming(YkCtrlPointVars, BBStartTracing);
   Phi->addIncoming(YkCtrlPointVars, BBStopTracing);
   Builder.CreateRet(Phi);
 }