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//===- interfaces.go - IR generation for interfaces -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements IR generation for dealing with interface values.
//
//===----------------------------------------------------------------------===//
package irgen
import (
"llvm.org/llgo/third_party/gotools/go/types"
"llvm.org/llvm/bindings/go/llvm"
)
// interfaceMethod returns a function and receiver pointer for the specified
// interface and method pair.
func (fr *frame) interfaceMethod(lliface llvm.Value, ifacety types.Type, method *types.Func) (fn, recv *govalue) {
llitab := fr.builder.CreateExtractValue(lliface, 0, "")
recv = newValue(fr.builder.CreateExtractValue(lliface, 1, ""), types.Typ[types.UnsafePointer])
methodset := fr.types.MethodSet(ifacety)
// TODO(axw) cache ordered method index
index := -1
for i, m := range orderedMethodSet(methodset) {
if m.Obj() == method {
index = i
break
}
}
if index == -1 {
panic("could not find method index")
}
llitab = fr.builder.CreateBitCast(llitab, llvm.PointerType(llvm.PointerType(llvm.Int8Type(), 0), 0), "")
// Skip runtime type pointer.
llifnptr := fr.builder.CreateGEP(llitab, []llvm.Value{
llvm.ConstInt(llvm.Int32Type(), uint64(index+1), false),
}, "")
llifn := fr.builder.CreateLoad(llifnptr, "")
// Replace receiver type with unsafe.Pointer.
recvparam := types.NewParam(0, nil, "", types.Typ[types.UnsafePointer])
sig := method.Type().(*types.Signature)
sig = types.NewSignature(nil, recvparam, sig.Params(), sig.Results(), sig.Variadic())
fn = newValue(llifn, sig)
return
}
// compareInterfaces emits code to compare two interfaces for
// equality.
func (fr *frame) compareInterfaces(a, b *govalue) *govalue {
aNull := a.value.IsNull()
bNull := b.value.IsNull()
if aNull && bNull {
return newValue(boolLLVMValue(true), types.Typ[types.Bool])
}
compare := fr.runtime.emptyInterfaceCompare
aI := a.Type().Underlying().(*types.Interface).NumMethods() > 0
bI := b.Type().Underlying().(*types.Interface).NumMethods() > 0
switch {
case aI && bI:
compare = fr.runtime.interfaceCompare
case aI:
a = fr.convertI2E(a)
case bI:
b = fr.convertI2E(b)
}
result := compare.call(fr, a.value, b.value)[0]
result = fr.builder.CreateIsNull(result, "")
result = fr.builder.CreateZExt(result, llvm.Int8Type(), "")
return newValue(result, types.Typ[types.Bool])
}
func (fr *frame) makeInterface(llv llvm.Value, vty types.Type, iface types.Type) *govalue {
if _, ok := vty.Underlying().(*types.Pointer); !ok {
ptr := fr.createTypeMalloc(vty)
fr.builder.CreateStore(llv, ptr)
llv = ptr
}
return fr.makeInterfaceFromPointer(llv, vty, iface)
}
func (fr *frame) makeInterfaceFromPointer(vptr llvm.Value, vty types.Type, iface types.Type) *govalue {
i8ptr := llvm.PointerType(llvm.Int8Type(), 0)
llv := fr.builder.CreateBitCast(vptr, i8ptr, "")
value := llvm.Undef(fr.types.ToLLVM(iface))
itab := fr.types.getItabPointer(vty, iface.Underlying().(*types.Interface))
value = fr.builder.CreateInsertValue(value, itab, 0, "")
value = fr.builder.CreateInsertValue(value, llv, 1, "")
return newValue(value, iface)
}
// Reads the type descriptor from the given interface type.
func (fr *frame) getInterfaceTypeDescriptor(v *govalue) llvm.Value {
isempty := v.Type().Underlying().(*types.Interface).NumMethods() == 0
itab := fr.builder.CreateExtractValue(v.value, 0, "")
if isempty {
return itab
} else {
itabnonnull := fr.builder.CreateIsNotNull(itab, "")
return fr.loadOrNull(itabnonnull, itab, types.Typ[types.UnsafePointer]).value
}
}
// Reads the value from the given interface type, assuming that the
// interface holds a value of the correct type.
func (fr *frame) getInterfaceValue(v *govalue, ty types.Type) *govalue {
val := fr.builder.CreateExtractValue(v.value, 1, "")
if _, ok := ty.Underlying().(*types.Pointer); !ok {
typedval := fr.builder.CreateBitCast(val, llvm.PointerType(fr.types.ToLLVM(ty), 0), "")
val = fr.builder.CreateLoad(typedval, "")
}
return newValue(val, ty)
}
// If cond is true, reads the value from the given interface type, otherwise
// returns a nil value.
func (fr *frame) getInterfaceValueOrNull(cond llvm.Value, v *govalue, ty types.Type) *govalue {
val := fr.builder.CreateExtractValue(v.value, 1, "")
if _, ok := ty.Underlying().(*types.Pointer); ok {
val = fr.builder.CreateSelect(cond, val, llvm.ConstNull(val.Type()), "")
} else {
val = fr.loadOrNull(cond, val, ty).value
}
return newValue(val, ty)
}
func (fr *frame) interfaceTypeCheck(val *govalue, ty types.Type) (v *govalue, okval *govalue) {
tytd := fr.types.ToRuntime(ty)
if _, ok := ty.Underlying().(*types.Interface); ok {
var result []llvm.Value
if val.Type().Underlying().(*types.Interface).NumMethods() > 0 {
result = fr.runtime.ifaceI2I2.call(fr, tytd, val.value)
} else {
result = fr.runtime.ifaceE2I2.call(fr, tytd, val.value)
}
v = newValue(result[0], ty)
okval = newValue(result[1], types.Typ[types.Bool])
} else {
valtd := fr.getInterfaceTypeDescriptor(val)
tyequal := fr.runtime.typeDescriptorsEqual.call(fr, valtd, tytd)[0]
okval = newValue(tyequal, types.Typ[types.Bool])
tyequal = fr.builder.CreateTrunc(tyequal, llvm.Int1Type(), "")
v = fr.getInterfaceValueOrNull(tyequal, val, ty)
}
return
}
func (fr *frame) interfaceTypeAssert(val *govalue, ty types.Type) *govalue {
if _, ok := ty.Underlying().(*types.Interface); ok {
return fr.changeInterface(val, ty, true)
} else {
valtytd := fr.types.ToRuntime(val.Type())
valtd := fr.getInterfaceTypeDescriptor(val)
tytd := fr.types.ToRuntime(ty)
fr.runtime.checkInterfaceType.call(fr, valtd, tytd, valtytd)
return fr.getInterfaceValue(val, ty)
}
}
// convertI2E converts a non-empty interface value to an empty interface.
func (fr *frame) convertI2E(v *govalue) *govalue {
td := fr.getInterfaceTypeDescriptor(v)
val := fr.builder.CreateExtractValue(v.value, 1, "")
typ := types.NewInterface(nil, nil)
intf := llvm.Undef(fr.types.ToLLVM(typ))
intf = fr.builder.CreateInsertValue(intf, td, 0, "")
intf = fr.builder.CreateInsertValue(intf, val, 1, "")
return newValue(intf, typ)
}
func (fr *frame) changeInterface(v *govalue, ty types.Type, assert bool) *govalue {
td := fr.getInterfaceTypeDescriptor(v)
tytd := fr.types.ToRuntime(ty)
var itab llvm.Value
if assert {
itab = fr.runtime.assertInterface.call(fr, tytd, td)[0]
} else {
itab = fr.runtime.convertInterface.call(fr, tytd, td)[0]
}
val := fr.builder.CreateExtractValue(v.value, 1, "")
intf := llvm.Undef(fr.types.ToLLVM(ty))
intf = fr.builder.CreateInsertValue(intf, itab, 0, "")
intf = fr.builder.CreateInsertValue(intf, val, 1, "")
return newValue(intf, ty)
}
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