// fixAndAndAssign rewrites if(x && (y = z) ...) ... to if(x) { y = z; if(...) ... }
func fixAndAndAssign(stmt *cc.Stmt) {
changed := false
clauses := splitExpr(stmt.Expr, cc.AndAnd)
for i := len(clauses) - 1; i > 0; i-- {
before, _ := extractSideEffects(clauses[i], sideNoAfter)
if len(before) == 0 {
continue
}
changed = true
stmt.Body = &cc.Stmt{
Op: BlockNoBrace,
Block: append(before, &cc.Stmt{
Op: cc.If,
Expr: joinExpr(clauses[i:], cc.AndAnd),
Body: stmt.Body,
}),
}
clauses = clauses[:i]
}
if changed {
stmt.Expr = joinExpr(clauses, cc.AndAnd)
}
}
func fixMemset(prog *cc.Prog, fn *cc.Decl, stmt *cc.Stmt) {
x := stmt.Expr
if len(x.List) != 3 || x.List[1].Op != cc.Number || x.List[1].Text != "0" {
// fprintf(x.Span, "unsupported %v - nonzero", x)
return
}
if x.List[2].Op == cc.SizeofExpr || x.List[2].Op == cc.SizeofType {
obj, objType := objIndir(fn, x.List[0])
if !matchSize(fn, obj, objType, x.List[2]) {
// fprintf(x.Span, "unsupported %v - wrong size", x)
return
}
x.Op = cc.Eq
x.Left = obj
x.Right = zeroFor(objType)
x.List = nil
return
}
siz := x.List[2]
var count *cc.Expr
var objType *cc.Type
if siz.Op == cc.Mul {
count = siz.Left
siz = siz.Right
if siz.Op != cc.SizeofExpr && siz.Op != cc.SizeofType {
// fprintf(x.Span, "unsupported %v - wrong array size", x)
return
}
switch siz.Op {
case cc.SizeofExpr:
p := unparen(siz.Left)
if p.Op != cc.Indir && p.Op != cc.Index || !sameType(p.Left.XType, x.List[0].XType) {
// fprintf(x.Span, "unsupported %v - wrong size", x)
}
objType = fixGoTypesExpr(fn, x.List[0], nil)
case cc.SizeofType:
objType = fixGoTypesExpr(fn, x.List[0], nil)
if !sameType(siz.Type, objType.Base) {
// fprintf(x.Span, "unsupported %v - wrong size", x)
}
}
} else {
count = siz
objType = fixGoTypesExpr(fn, x.List[0], nil)
if !objType.Base.Is(Byte) && !objType.Base.Is(Uint8) {
// fprintf(x.Span, "unsupported %v - wrong size form for non-byte type", x)
return
}
}
if objType == nil {
fprintf(x.Span, "unsupported %v - lost type", x)
return
}
// Found it. Replace with zeroing for loop.
stmt.Op = cc.For
stmt.Pre = &cc.Expr{
Op: cc.Eq,
Left: &cc.Expr{
Op: cc.Name,
Text: "i",
XType: intType,
},
Right: &cc.Expr{
Op: cc.Number,
Text: "0",
XType: intType,
},
XType: boolType,
}
stmt.Expr = &cc.Expr{
Op: cc.Lt,
Left: &cc.Expr{
Op: cc.Name,
Text: "i",
XType: intType,
},
Right: count,
XType: boolType,
}
stmt.Post = &cc.Expr{
Op: cc.PostInc,
Left: &cc.Expr{
Op: cc.Name,
Text: "i",
XType: intType,
},
XType: intType,
}
stmt.Body = &cc.Stmt{
Op: cc.Block,
Block: []*cc.Stmt{
{
Op: cc.StmtExpr,
Expr: &cc.Expr{
Op: cc.Eq,
Left: &cc.Expr{
Op: cc.Index,
Left: x.List[0],
Right: &cc.Expr{Op: cc.Name, Text: "i"},
},
Right: zeroFor(objType.Base),
},
},
},
}
return
}
func rewriteStmt(stmt *cc.Stmt) {
// TODO: Double-check stmt.Labels
switch stmt.Op {
case cc.ARGBEGIN:
panic(fmt.Sprintf("unexpected ARGBEGIN"))
case cc.Do:
// Rewrite do { ... } while(x)
// to for(;;) { ... if(!x) break }
// Since rewriteStmt is called in a preorder traversal,
// the recursion into the children will clean up x
// in the if condition as needed.
stmt.Op = cc.For
x := stmt.Expr
stmt.Expr = nil
stmt.Body = forceBlock(stmt.Body)
stmt.Body.Block = append(stmt.Body.Block, &cc.Stmt{
Op: cc.If,
Expr: &cc.Expr{Op: cc.Not, Left: x},
Body: &cc.Stmt{Op: cc.Break},
})
case cc.While:
stmt.Op = cc.For
fallthrough
case cc.For:
before1, _ := extractSideEffects(stmt.Pre, sideStmt|sideNoAfter)
before2, _ := extractSideEffects(stmt.Expr, sideNoAfter)
if len(before2) > 0 {
x := stmt.Expr
stmt.Expr = nil
stmt.Body = forceBlock(stmt.Body)
top := &cc.Stmt{
Op: cc.If,
Expr: &cc.Expr{Op: cc.Not, Left: x},
Body: &cc.Stmt{Op: cc.Break},
}
stmt.Body.Block = append(append(before2, top), stmt.Body.Block...)
}
if len(before1) > 0 {
old := copyStmt(stmt)
stmt.Pre = nil
stmt.Expr = nil
stmt.Post = nil
stmt.Body = nil
stmt.Op = BlockNoBrace
stmt.Block = append(before1, old)
}
before, after := extractSideEffects(stmt.Post, sideStmt)
if len(before)+len(after) > 0 {
all := append(append(before, &cc.Stmt{Op: cc.StmtExpr, Expr: stmt.Post}), after...)
stmt.Post = &cc.Expr{Op: ExprBlock, Block: all}
}
case cc.If, cc.Return:
if stmt.Op == cc.If && stmt.Else == nil {
fixAndAndAssign(stmt)
}
before, _ := extractSideEffects(stmt.Expr, sideNoAfter)
if len(before) > 0 {
old := copyStmt(stmt)
stmt.Expr = nil
stmt.Body = nil
stmt.Else = nil
stmt.Op = BlockNoBrace
stmt.Block = append(before, old)
}
case cc.StmtExpr:
before, after := extractSideEffects(stmt.Expr, sideStmt)
if len(before)+len(after) > 0 {
old := copyStmt(stmt)
stmt.Expr = nil
stmt.Op = BlockNoBrace
stmt.Block = append(append(before, old), after...)
}
case cc.Goto:
// TODO: Figure out where the goto goes and maybe rewrite
// to labeled break/continue.
// Otherwise move code or something.
case cc.Switch:
// TODO: Change default fallthrough to default break.
before, _ := extractSideEffects(stmt.Expr, sideNoAfter)
if len(before) > 0 {
old := copyStmt(stmt)
stmt.Expr = nil
stmt.Body = nil
stmt.Else = nil
stmt.Op = BlockNoBrace
stmt.Block = append(before, old)
break // recursion will rewrite new inner switch
}
rewriteSwitch(stmt)
}
}