slice.go
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//===- slice.go - IR generation for slices --------------------------------===//
//
// 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 slices.
//
//===----------------------------------------------------------------------===//
package irgen
import (
"llvm.org/llgo/third_party/gotools/go/types"
"llvm.org/llvm/bindings/go/llvm"
)
// makeSlice allocates a new slice with the optional length and capacity,
// initialising its contents to their zero values.
func (fr *frame) makeSlice(sliceType types.Type, length, capacity *govalue) *govalue {
length = fr.convert(length, types.Typ[types.Uintptr])
capacity = fr.convert(capacity, types.Typ[types.Uintptr])
runtimeType := fr.types.ToRuntime(sliceType)
llslice := fr.runtime.makeSlice.call(fr, runtimeType, length.value, capacity.value)
return newValue(llslice[0], sliceType)
}
func (fr *frame) slice(x llvm.Value, xtyp types.Type, low, high, max llvm.Value) llvm.Value {
if !low.IsNil() {
low = fr.createZExtOrTrunc(low, fr.types.inttype, "")
} else {
low = llvm.ConstNull(fr.types.inttype)
}
if !high.IsNil() {
high = fr.createZExtOrTrunc(high, fr.types.inttype, "")
}
if !max.IsNil() {
max = fr.createZExtOrTrunc(max, fr.types.inttype, "")
}
var arrayptr, arraylen, arraycap llvm.Value
var elemtyp types.Type
var errcode uint64
switch typ := xtyp.Underlying().(type) {
case *types.Pointer: // *array
errcode = gccgoRuntimeErrorARRAY_SLICE_OUT_OF_BOUNDS
arraytyp := typ.Elem().Underlying().(*types.Array)
elemtyp = arraytyp.Elem()
arrayptr = x
arrayptr = fr.builder.CreateBitCast(arrayptr, llvm.PointerType(llvm.Int8Type(), 0), "")
arraylen = llvm.ConstInt(fr.llvmtypes.inttype, uint64(arraytyp.Len()), false)
arraycap = arraylen
case *types.Slice:
errcode = gccgoRuntimeErrorSLICE_SLICE_OUT_OF_BOUNDS
elemtyp = typ.Elem()
arrayptr = fr.builder.CreateExtractValue(x, 0, "")
arraylen = fr.builder.CreateExtractValue(x, 1, "")
arraycap = fr.builder.CreateExtractValue(x, 2, "")
case *types.Basic:
if high.IsNil() {
high = llvm.ConstAllOnes(fr.types.inttype) // -1
}
result := fr.runtime.stringSlice.call(fr, x, low, high)
return result[0]
default:
panic("unimplemented")
}
if high.IsNil() {
high = arraylen
}
if max.IsNil() {
max = arraycap
}
// Bounds checking: 0 <= low <= high <= max <= cap
zero := llvm.ConstNull(fr.types.inttype)
l0 := fr.builder.CreateICmp(llvm.IntSLT, low, zero, "")
hl := fr.builder.CreateICmp(llvm.IntSLT, high, low, "")
mh := fr.builder.CreateICmp(llvm.IntSLT, max, high, "")
cm := fr.builder.CreateICmp(llvm.IntSLT, arraycap, max, "")
cond := fr.builder.CreateOr(l0, hl, "")
cond = fr.builder.CreateOr(cond, mh, "")
cond = fr.builder.CreateOr(cond, cm, "")
fr.condBrRuntimeError(cond, errcode)
slicelen := fr.builder.CreateSub(high, low, "")
slicecap := fr.builder.CreateSub(max, low, "")
elemsize := llvm.ConstInt(fr.llvmtypes.inttype, uint64(fr.llvmtypes.Sizeof(elemtyp)), false)
offset := fr.builder.CreateMul(low, elemsize, "")
sliceptr := fr.builder.CreateInBoundsGEP(arrayptr, []llvm.Value{offset}, "")
llslicetyp := fr.llvmtypes.sliceBackendType().ToLLVM(fr.llvmtypes.ctx)
sliceValue := llvm.Undef(llslicetyp)
sliceValue = fr.builder.CreateInsertValue(sliceValue, sliceptr, 0, "")
sliceValue = fr.builder.CreateInsertValue(sliceValue, slicelen, 1, "")
sliceValue = fr.builder.CreateInsertValue(sliceValue, slicecap, 2, "")
return sliceValue
}