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package compiler
import (
"fmt"
"strings"
"tinygo.org/x/go-llvm"
)
// createAtomicOp lowers a sync/atomic function by lowering it as an LLVM atomic
// operation. It returns the result of the operation, or a zero llvm.Value if
// the result is void.
func (b *builder) createAtomicOp(name string) llvm.Value {
switch name {
case "AddInt32", "AddInt64", "AddUint32", "AddUint64", "AddUintptr":
ptr := b.getValue(b.fn.Params[0])
val := b.getValue(b.fn.Params[1])
if strings.HasPrefix(b.Triple, "avr") {
// AtomicRMW does not work on AVR as intended:
// - There are some register allocation issues (fixed by https://reviews.llvm.org/D97127 which is not yet in a usable LLVM release)
// - The result is the new value instead of the old value
vType := val.Type()
name := fmt.Sprintf("__sync_fetch_and_add_%d", vType.IntTypeWidth()/8)
fn := b.mod.NamedFunction(name)
if fn.IsNil() {
fn = llvm.AddFunction(b.mod, name, llvm.FunctionType(vType, []llvm.Type{ptr.Type(), vType}, false))
}
oldVal := b.createCall(fn.GlobalValueType(), fn, []llvm.Value{ptr, val}, "")
// Return the new value, not the original value returned.
return b.CreateAdd(oldVal, val, "")
}
oldVal := b.CreateAtomicRMW(llvm.AtomicRMWBinOpAdd, ptr, val, llvm.AtomicOrderingSequentiallyConsistent, true)
// Return the new value, not the original value returned by atomicrmw.
return b.CreateAdd(oldVal, val, "")
case "SwapInt32", "SwapInt64", "SwapUint32", "SwapUint64", "SwapUintptr", "SwapPointer":
ptr := b.getValue(b.fn.Params[0])
val := b.getValue(b.fn.Params[1])
isPointer := val.Type().TypeKind() == llvm.PointerTypeKind
if isPointer {
// atomicrmw only supports integers, so cast to an integer.
// TODO: this is fixed in LLVM 15.
val = b.CreatePtrToInt(val, b.uintptrType, "")
ptr = b.CreateBitCast(ptr, llvm.PointerType(val.Type(), 0), "")
}
oldVal := b.CreateAtomicRMW(llvm.AtomicRMWBinOpXchg, ptr, val, llvm.AtomicOrderingSequentiallyConsistent, true)
if isPointer {
oldVal = b.CreateIntToPtr(oldVal, b.i8ptrType, "")
}
return oldVal
case "CompareAndSwapInt32", "CompareAndSwapInt64", "CompareAndSwapUint32", "CompareAndSwapUint64", "CompareAndSwapUintptr", "CompareAndSwapPointer":
ptr := b.getValue(b.fn.Params[0])
old := b.getValue(b.fn.Params[1])
newVal := b.getValue(b.fn.Params[2])
tuple := b.CreateAtomicCmpXchg(ptr, old, newVal, llvm.AtomicOrderingSequentiallyConsistent, llvm.AtomicOrderingSequentiallyConsistent, true)
swapped := b.CreateExtractValue(tuple, 1, "")
return swapped
case "LoadInt32", "LoadInt64", "LoadUint32", "LoadUint64", "LoadUintptr", "LoadPointer":
ptr := b.getValue(b.fn.Params[0])
val := b.CreateLoad(b.getLLVMType(b.fn.Signature.Results().At(0).Type()), ptr, "")
val.SetOrdering(llvm.AtomicOrderingSequentiallyConsistent)
val.SetAlignment(b.targetData.PrefTypeAlignment(val.Type())) // required
return val
case "StoreInt32", "StoreInt64", "StoreUint32", "StoreUint64", "StoreUintptr", "StorePointer":
ptr := b.getValue(b.fn.Params[0])
val := b.getValue(b.fn.Params[1])
if strings.HasPrefix(b.Triple, "avr") {
// SelectionDAGBuilder is currently missing the "are unaligned atomics allowed" check for stores.
vType := val.Type()
isPointer := vType.TypeKind() == llvm.PointerTypeKind
if isPointer {
// libcalls only supports integers, so cast to an integer.
vType = b.uintptrType
val = b.CreatePtrToInt(val, vType, "")
ptr = b.CreateBitCast(ptr, llvm.PointerType(vType, 0), "")
}
name := fmt.Sprintf("__atomic_store_%d", vType.IntTypeWidth()/8)
fn := b.mod.NamedFunction(name)
if fn.IsNil() {
fn = llvm.AddFunction(b.mod, name, llvm.FunctionType(vType, []llvm.Type{ptr.Type(), vType, b.uintptrType}, false))
}
b.createCall(fn.GlobalValueType(), fn, []llvm.Value{ptr, val, llvm.ConstInt(b.uintptrType, 5, false)}, "")
return llvm.Value{}
}
store := b.CreateStore(val, ptr)
store.SetOrdering(llvm.AtomicOrderingSequentiallyConsistent)
store.SetAlignment(b.targetData.PrefTypeAlignment(val.Type())) // required
return llvm.Value{}
default:
b.addError(b.fn.Pos(), "unknown atomic operation: "+b.fn.Name())
return llvm.Value{}
}
}
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