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Implement strings the way Go itself does

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This makes string slicing cheap.
This commit is contained in:
Ayke van Laethem
2018-04-14 19:24:21 +02:00
parent 7cc2301621
commit 60a01a43a3
3 changed files with 10 additions and 15 deletions
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tgo.go
+6 -11
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@@ -34,7 +34,6 @@ type Compiler struct {
intType llvm.Type
stringLenType llvm.Type
stringType llvm.Type
stringPtrType llvm.Type
printstringFunc llvm.Value
printintFunc llvm.Value
printspaceFunc llvm.Value
@@ -73,10 +72,9 @@ func NewCompiler(path, triple string) (*Compiler, error) {
c.stringLenType = llvm.Int32Type()
// Length-prefixed string.
c.stringType = llvm.StructType([]llvm.Type{c.stringLenType, llvm.ArrayType(llvm.Int8Type(), 0)}, false)
c.stringPtrType = llvm.PointerType(c.stringType, 0)
c.stringType = llvm.StructType([]llvm.Type{c.stringLenType, llvm.PointerType(llvm.Int8Type(), 0)}, false)
printstringType := llvm.FunctionType(llvm.VoidType(), []llvm.Type{c.stringPtrType}, false)
printstringType := llvm.FunctionType(llvm.VoidType(), []llvm.Type{c.stringType}, false)
c.printstringFunc = llvm.AddFunction(c.mod, "__go_printstring", printstringType)
printintType := llvm.FunctionType(llvm.VoidType(), []llvm.Type{c.intType}, false)
c.printintFunc = llvm.AddFunction(c.mod, "__go_printint", printintType)
@@ -306,7 +304,7 @@ func (c *Compiler) parseBuiltin(frame *Frame, instr *ssa.CallCommon, call *ssa.B
return llvm.Value{}, err
}
switch expr.Type() {
case c.stringPtrType:
case c.stringType:
c.builder.CreateCall(c.printstringFunc, []llvm.Value{expr}, "")
case c.intType:
c.builder.CreateCall(c.printintFunc, []llvm.Value{expr}, "")
@@ -426,13 +424,10 @@ func (c *Compiler) parseExpr(frame *Frame, expr ssa.Value) (llvm.Value, error) {
switch expr.Value.Kind() {
case constant.String:
str := constant.StringVal(expr.Value)
strVal := c.ctx.ConstString(str, false)
strLen := llvm.ConstInt(c.stringLenType, uint64(len(str)), false)
strObj := llvm.ConstStruct([]llvm.Value{strLen, strVal}, false)
ptr := llvm.AddGlobal(c.mod, strObj.Type(), ".str")
ptr.SetInitializer(strObj)
ptr.SetLinkage(llvm.InternalLinkage)
return llvm.ConstPointerCast(ptr, c.stringPtrType), nil
strPtr := c.builder.CreateGlobalStringPtr(str, ".str")
strObj := llvm.ConstStruct([]llvm.Value{strLen, strPtr}, false)
return strObj, nil
case constant.Int:
n, _ := constant.Int64Val(expr.Value) // TODO: do something with the 'exact' return value?
return llvm.ConstInt(c.intType, uint64(n), true), nil