1//===- slice.go - IR generation for slices --------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements IR generation for slices.
10//
11//===----------------------------------------------------------------------===//
12
13package irgen
14
15import (
16	"llvm.org/llgo/third_party/gotools/go/types"
17	"llvm.org/llvm/bindings/go/llvm"
18)
19
20// makeSlice allocates a new slice with the optional length and capacity,
21// initialising its contents to their zero values.
22func (fr *frame) makeSlice(sliceType types.Type, length, capacity *govalue) *govalue {
23	length = fr.convert(length, types.Typ[types.Uintptr])
24	capacity = fr.convert(capacity, types.Typ[types.Uintptr])
25	runtimeType := fr.types.ToRuntime(sliceType)
26	llslice := fr.runtime.makeSlice.call(fr, runtimeType, length.value, capacity.value)
27	return newValue(llslice[0], sliceType)
28}
29
30func (fr *frame) slice(x llvm.Value, xtyp types.Type, low, high, max llvm.Value) llvm.Value {
31	if !low.IsNil() {
32		low = fr.createZExtOrTrunc(low, fr.types.inttype, "")
33	} else {
34		low = llvm.ConstNull(fr.types.inttype)
35	}
36	if !high.IsNil() {
37		high = fr.createZExtOrTrunc(high, fr.types.inttype, "")
38	}
39	if !max.IsNil() {
40		max = fr.createZExtOrTrunc(max, fr.types.inttype, "")
41	}
42
43	var arrayptr, arraylen, arraycap llvm.Value
44	var elemtyp types.Type
45	var errcode uint64
46	switch typ := xtyp.Underlying().(type) {
47	case *types.Pointer: // *array
48		errcode = gccgoRuntimeErrorARRAY_SLICE_OUT_OF_BOUNDS
49		arraytyp := typ.Elem().Underlying().(*types.Array)
50		elemtyp = arraytyp.Elem()
51		arrayptr = x
52		arrayptr = fr.builder.CreateBitCast(arrayptr, llvm.PointerType(llvm.Int8Type(), 0), "")
53		arraylen = llvm.ConstInt(fr.llvmtypes.inttype, uint64(arraytyp.Len()), false)
54		arraycap = arraylen
55	case *types.Slice:
56		errcode = gccgoRuntimeErrorSLICE_SLICE_OUT_OF_BOUNDS
57		elemtyp = typ.Elem()
58		arrayptr = fr.builder.CreateExtractValue(x, 0, "")
59		arraylen = fr.builder.CreateExtractValue(x, 1, "")
60		arraycap = fr.builder.CreateExtractValue(x, 2, "")
61	case *types.Basic:
62		if high.IsNil() {
63			high = llvm.ConstAllOnes(fr.types.inttype) // -1
64		}
65		result := fr.runtime.stringSlice.call(fr, x, low, high)
66		return result[0]
67	default:
68		panic("unimplemented")
69	}
70	if high.IsNil() {
71		high = arraylen
72	}
73	if max.IsNil() {
74		max = arraycap
75	}
76
77	// Bounds checking: 0 <= low <= high <= max <= cap
78	zero := llvm.ConstNull(fr.types.inttype)
79	l0 := fr.builder.CreateICmp(llvm.IntSLT, low, zero, "")
80	hl := fr.builder.CreateICmp(llvm.IntSLT, high, low, "")
81	mh := fr.builder.CreateICmp(llvm.IntSLT, max, high, "")
82	cm := fr.builder.CreateICmp(llvm.IntSLT, arraycap, max, "")
83
84	cond := fr.builder.CreateOr(l0, hl, "")
85	cond = fr.builder.CreateOr(cond, mh, "")
86	cond = fr.builder.CreateOr(cond, cm, "")
87
88	fr.condBrRuntimeError(cond, errcode)
89
90	slicelen := fr.builder.CreateSub(high, low, "")
91	slicecap := fr.builder.CreateSub(max, low, "")
92
93	elemsize := llvm.ConstInt(fr.llvmtypes.inttype, uint64(fr.llvmtypes.Sizeof(elemtyp)), false)
94	offset := fr.builder.CreateMul(low, elemsize, "")
95
96	sliceptr := fr.builder.CreateInBoundsGEP(arrayptr, []llvm.Value{offset}, "")
97
98	llslicetyp := fr.llvmtypes.sliceBackendType().ToLLVM(fr.llvmtypes.ctx)
99	sliceValue := llvm.Undef(llslicetyp)
100	sliceValue = fr.builder.CreateInsertValue(sliceValue, sliceptr, 0, "")
101	sliceValue = fr.builder.CreateInsertValue(sliceValue, slicelen, 1, "")
102	sliceValue = fr.builder.CreateInsertValue(sliceValue, slicecap, 2, "")
103
104	return sliceValue
105}
106