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compiler: implement string slicing

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This commit is contained in:
Ayke van Laethem
2018-09-02 23:46:31 +02:00
parent 1170cdc21f
commit a080ce26ef
1 changed files with 42 additions and 23 deletions
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compiler.go
+42 -23
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@@ -1919,27 +1919,28 @@ func (c *Compiler) parseExpr(frame *Frame, expr ssa.Value) (llvm.Value, error) {
if err != nil {
return llvm.Value{}, err
}
var low, high llvm.Value
if expr.Low == nil {
low = llvm.ConstInt(c.lenType, 0, false)
} else {
low, err = c.parseExpr(frame, expr.Low)
if err != nil {
return llvm.Value{}, nil
}
}
if expr.High != nil {
high, err = c.parseExpr(frame, expr.High)
if err != nil {
return llvm.Value{}, nil
}
}
switch typ := expr.X.Type().Underlying().(type) {
case *types.Pointer: // pointer to array
// slice an array
length := typ.Elem().(*types.Array).Len()
llvmLen := llvm.ConstInt(c.lenType, uint64(length), false)
var low, high llvm.Value
if expr.Low == nil {
low = llvm.ConstInt(c.lenType, 0, false)
} else {
low, err = c.parseExpr(frame, expr.Low)
if err != nil {
return llvm.Value{}, nil
}
}
if expr.High == nil {
if high.IsNil() {
high = llvmLen
} else {
high, err = c.parseExpr(frame, expr.High)
if err != nil {
return llvm.Value{}, nil
}
}
indices := []llvm.Value{
llvm.ConstInt(llvm.Int32Type(), 0, false),
@@ -1948,10 +1949,6 @@ func (c *Compiler) parseExpr(frame *Frame, expr ssa.Value) (llvm.Value, error) {
slicePtr := c.builder.CreateGEP(value, indices, "slice.ptr")
sliceLen := c.builder.CreateSub(high, low, "slice.len")
sliceCap := c.builder.CreateSub(llvmLen, low, "slice.cap")
sliceTyp, err := c.getLLVMType(expr.Type())
if err != nil {
return llvm.Value{}, err
}
// This check is optimized away in most cases.
if !frame.fn.nobounds {
@@ -1959,24 +1956,46 @@ func (c *Compiler) parseExpr(frame *Frame, expr ssa.Value) (llvm.Value, error) {
c.builder.CreateCall(sliceBoundsCheck, []llvm.Value{llvmLen, low, high}, "")
}
slice := llvm.ConstNamedStruct(sliceTyp, []llvm.Value{
slice := llvm.ConstStruct([]llvm.Value{
llvm.Undef(slicePtr.Type()),
llvm.Undef(c.lenType),
llvm.Undef(c.lenType),
})
}, false)
slice = c.builder.CreateInsertValue(slice, slicePtr, 0, "")
slice = c.builder.CreateInsertValue(slice, sliceLen, 1, "")
slice = c.builder.CreateInsertValue(slice, sliceCap, 2, "")
return slice, nil
case *types.Slice:
// slice a slice
return llvm.Value{}, errors.New("todo: slice a slice: " + typ.String())
case *types.Basic:
// slice a string
if typ.Kind() != types.String {
return llvm.Value{}, errors.New("unknown slice type: " + typ.String())
}
return llvm.Value{}, errors.New("todo: slice a string")
// slice a string
oldLen := c.builder.CreateExtractValue(value, 0, "")
oldPtr := c.builder.CreateExtractValue(value, 1, "")
if high.IsNil() {
high = oldLen
}
if !frame.fn.nobounds {
sliceBoundsCheck := c.mod.NamedFunction("runtime.sliceBoundsCheck")
c.builder.CreateCall(sliceBoundsCheck, []llvm.Value{oldLen, low, high}, "")
}
newLen := c.builder.CreateSub(high, low, "")
newPtr := c.builder.CreateGEP(oldPtr, []llvm.Value{low}, "")
str, err := getZeroValue(c.mod.GetTypeByName("runtime._string"))
if err != nil {
return llvm.Value{}, err
}
str = c.builder.CreateInsertValue(str, newLen, 0, "")
str = c.builder.CreateInsertValue(str, newPtr, 1, "")
return str, nil
default:
return llvm.Value{}, errors.New("unknown slice type: " + typ.String())
}