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compiler: add support for 'go' on func values

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This commit allows starting a new goroutine directly from a func value,
not just when the static callee is known.

This is necessary to support the whole time package, not just the
commonly used subset that was compiled with the SimpleDCE pass enabled.
This commit is contained in:
Ayke van Laethem
2019-08-15 15:52:26 +02:00
committed by Ron Evans
parent e4fc3bb66a
commit bbc3046687
6 changed files with 238 additions and 131 deletions
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compiler/goroutine.go
+82 -30
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@@ -18,14 +18,12 @@ func (c *Compiler) emitStartGoroutine(funcPtr llvm.Value, params []llvm.Value) l
calleeValue := c.createGoroutineStartWrapper(funcPtr)
c.createRuntimeCall("startGoroutine", []llvm.Value{calleeValue, paramBundle}, "")
case "coroutines":
// Mark this function as a 'go' invocation and break invalid
// interprocedural optimizations. For example, heap-to-stack
// transformations are not sound as goroutines can outlive their parent.
calleeType := funcPtr.Type()
// We roundtrip through runtime.makeGoroutine as a signal (to find these
// calls) and to break any optimizations LLVM will try to do: they are
// invalid if we called this as a regular function to be updated later.
calleeValue := c.builder.CreatePtrToInt(funcPtr, c.uintptrType, "")
calleeValue = c.createRuntimeCall("makeGoroutine", []llvm.Value{calleeValue}, "")
calleeValue = c.builder.CreateIntToPtr(calleeValue, calleeType, "")
calleeValue = c.builder.CreateIntToPtr(calleeValue, funcPtr.Type(), "")
c.createCall(calleeValue, params, "")
default:
panic("unreachable")
@@ -52,32 +50,86 @@ func (c *Compiler) emitStartGoroutine(funcPtr llvm.Value, params []llvm.Value) l
// ignores the return value because newly started goroutines do not have a
// return value.
func (c *Compiler) createGoroutineStartWrapper(fn llvm.Value) llvm.Value {
if fn.IsAFunction().IsNil() {
panic("todo: goroutine start wrapper for func value")
var wrapper llvm.Value
if !fn.IsAFunction().IsNil() {
// See whether this wrapper has already been created. If so, return it.
name := fn.Name()
wrapper = c.mod.NamedFunction(name + "$gowrapper")
if !wrapper.IsNil() {
return c.builder.CreateIntToPtr(wrapper, c.uintptrType, "")
}
// Save the current position in the IR builder.
currentBlock := c.builder.GetInsertBlock()
defer c.builder.SetInsertPointAtEnd(currentBlock)
// Create the wrapper.
wrapperType := llvm.FunctionType(c.ctx.VoidType(), []llvm.Type{c.i8ptrType}, false)
wrapper = llvm.AddFunction(c.mod, name+"$gowrapper", wrapperType)
wrapper.SetLinkage(llvm.PrivateLinkage)
wrapper.SetUnnamedAddr(true)
entry := llvm.AddBasicBlock(wrapper, "entry")
c.builder.SetInsertPointAtEnd(entry)
// Create the list of params for the call.
paramTypes := fn.Type().ElementType().ParamTypes()
params := c.emitPointerUnpack(wrapper.Param(0), paramTypes[:len(paramTypes)-2])
params = append(params, llvm.Undef(c.i8ptrType), llvm.ConstPointerNull(c.i8ptrType))
// Create the call.
c.builder.CreateCall(fn, params, "")
} else {
// For a function pointer like this:
//
// var funcPtr func(x, y int) int
//
// A wrapper like the following is created:
//
// func .gowrapper(ptr *unsafe.Pointer) {
// args := (*struct{
// x, y int
// fn func(x, y int) int
// })(ptr)
// args.fn(x, y)
// }
//
// With a bit of luck, identical wrapper functions like these can be
// merged into one.
// Save the current position in the IR builder.
currentBlock := c.builder.GetInsertBlock()
defer c.builder.SetInsertPointAtEnd(currentBlock)
// Create the wrapper.
wrapperType := llvm.FunctionType(c.ctx.VoidType(), []llvm.Type{c.i8ptrType}, false)
wrapper = llvm.AddFunction(c.mod, ".gowrapper", wrapperType)
wrapper.SetLinkage(llvm.InternalLinkage)
wrapper.SetUnnamedAddr(true)
entry := llvm.AddBasicBlock(wrapper, "entry")
c.builder.SetInsertPointAtEnd(entry)
// Get the list of parameters, with the extra parameters at the end.
paramTypes := fn.Type().ElementType().ParamTypes()
paramTypes[len(paramTypes)-1] = fn.Type() // the last element is the function pointer
params := c.emitPointerUnpack(wrapper.Param(0), paramTypes)
// Get the function pointer.
fnPtr := params[len(params)-1]
// Ignore the last param, which isn't used anymore.
// TODO: avoid this extra "parent handle" parameter in most functions.
params[len(params)-1] = llvm.Undef(c.i8ptrType)
// Create the call.
c.builder.CreateCall(fnPtr, params, "")
}
// See whether this wrapper has already been created. If so, return it.
name := fn.Name()
wrapper := c.mod.NamedFunction(name + "$gowrapper")
if !wrapper.IsNil() {
return c.builder.CreateIntToPtr(wrapper, c.uintptrType, "")
}
// Save the current position in the IR builder.
currentBlock := c.builder.GetInsertBlock()
defer c.builder.SetInsertPointAtEnd(currentBlock)
// Create the wrapper.
wrapperType := llvm.FunctionType(c.ctx.VoidType(), []llvm.Type{c.i8ptrType}, false)
wrapper = llvm.AddFunction(c.mod, name+"$gowrapper", wrapperType)
wrapper.SetLinkage(llvm.PrivateLinkage)
wrapper.SetUnnamedAddr(true)
entry := llvm.AddBasicBlock(wrapper, "entry")
c.builder.SetInsertPointAtEnd(entry)
paramTypes := fn.Type().ElementType().ParamTypes()
params := c.emitPointerUnpack(wrapper.Param(0), paramTypes[:len(paramTypes)-2])
params = append(params, llvm.Undef(c.i8ptrType), llvm.ConstPointerNull(c.i8ptrType))
c.builder.CreateCall(fn, params, "")
// Finish the function. Every basic block must end in a terminator, and
// because goroutines never return a value we can simply return void.
c.builder.CreateRetVoid()
// Return a ptrtoint of the wrapper, not the function itself.
return c.builder.CreatePtrToInt(wrapper, c.uintptrType, "")
}