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compiler: support recover()

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This commit is contained in:
Evgenii Stratonikov 2020-08-21 15:37:46 +03:00
parent 14ea3c2228
commit 5d82b82efb
4 changed files with 153 additions and 9 deletions
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71
pkg/compiler/codegen.go
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@ -77,6 +77,9 @@ type codegen struct {
// packages contains packages in the order they were loaded.
packages []string
// exceptionIndex is the index of static slot where exception is stored.
exceptionIndex int
// documents contains paths to all files used by the program.
documents []string
// docIndex maps file path to an index in documents array.
@ -216,6 +219,11 @@ func getBaseOpcode(t varType) (opcode.Opcode, opcode.Opcode) {
// emitLoadVar loads specified variable to the evaluation stack.
func (c *codegen) emitLoadVar(pkg string, name string) {
t, i := c.getVarIndex(pkg, name)
c.emitLoadByIndex(t, i)
}
// emitLoadByIndex loads specified variable type with index i.
func (c *codegen) emitLoadByIndex(t varType, i int) {
base, _ := getBaseOpcode(t)
if i < 7 {
emit.Opcode(c.prog.BinWriter, base+opcode.Opcode(i))
@ -231,6 +239,11 @@ func (c *codegen) emitStoreVar(pkg string, name string) {
return
}
t, i := c.getVarIndex(pkg, name)
c.emitStoreByIndex(t, i)
}
// emitLoadByIndex stores top value in the specified variable type with index i.
func (c *codegen) emitStoreByIndex(t varType, i int) {
_, base := getBaseOpcode(t)
if i < 7 {
emit.Opcode(c.prog.BinWriter, base+opcode.Opcode(i))
@ -831,11 +844,14 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
return nil
case *ast.DeferStmt:
catch := c.newLabel()
finally := c.newLabel()
param := make([]byte, 8)
binary.LittleEndian.PutUint16(param[0:], catch)
binary.LittleEndian.PutUint16(param[4:], finally)
emit.Instruction(c.prog.BinWriter, opcode.TRYL, param)
c.scope.deferStack = append(c.scope.deferStack, deferInfo{
catchLabel: catch,
finallyLabel: finally,
expr: n.Call,
})
@ -1103,14 +1119,45 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
}
// processDefers emits code for `defer` statements.
// TRY-related opcodes handle exception as follows:
// 1. CATCH block is executed only if exception has occured.
// 2. FINALLY block is always executed, but after catch block.
// Go `defer` statements are a bit different:
// 1. `defer` is always executed irregardless of whether an exception has occured.
// 2. `recover` can or can not handle a possible exception.
// Thus we use the following approach:
// 1. Throwed exception is saved in a static field X, static fields Y and is set to true.
// 2. CATCH and FINALLY blocks are the same, and both contain the same CALLs.
// 3. In CATCH block we set Y to true and emit default return values if it is the last defer.
// 4. Execute FINALLY block only if Y is false.
func (c *codegen) processDefers() {
for i := len(c.scope.deferStack) - 1; i >= 0; i-- {
stmt := c.scope.deferStack[i]
after := c.newLabel()
emit.Jmp(c.prog.BinWriter, opcode.ENDTRYL, after)
c.setLabel(stmt.finallyLabel)
// Execute body.
c.setLabel(stmt.catchLabel)
c.emitStoreByIndex(varGlobal, c.exceptionIndex)
emit.Int(c.prog.BinWriter, 1)
c.emitStoreByIndex(varLocal, c.scope.finallyProcessedIndex)
ast.Walk(c, stmt.expr)
if i == 0 {
// After panic, default values must be returns, except for named returns,
// which we don't support here for now.
for i := len(c.scope.decl.Type.Results.List) - 1; i >= 0; i-- {
c.emitDefault(c.typeOf(c.scope.decl.Type.Results.List[i].Type))
}
}
emit.Jmp(c.prog.BinWriter, opcode.ENDTRYL, after)
c.setLabel(stmt.finallyLabel)
before := c.newLabel()
c.emitLoadByIndex(varLocal, c.scope.finallyProcessedIndex)
emit.Jmp(c.prog.BinWriter, opcode.JMPIFL, before)
ast.Walk(c, stmt.expr)
c.setLabel(before)
emit.Int(c.prog.BinWriter, 0)
c.emitStoreByIndex(varLocal, c.scope.finallyProcessedIndex)
emit.Opcode(c.prog.BinWriter, opcode.ENDFINALLY)
c.setLabel(after)
}
@ -1464,6 +1511,10 @@ func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
}
case "panic":
emit.Opcode(c.prog.BinWriter, opcode.THROW)
case "recover":
c.emitLoadByIndex(varGlobal, c.exceptionIndex)
emit.Opcode(c.prog.BinWriter, opcode.PUSHNULL)
c.emitStoreByIndex(varGlobal, c.exceptionIndex)
case "ToInteger", "ToByteArray", "ToBool":
typ := stackitem.IntegerT
switch name {
@ -1803,8 +1854,13 @@ func (c *codegen) writeJumps(b []byte) ([]byte, error) {
opcode.JMPGT, opcode.JMPGE, opcode.JMPLE, opcode.JMPLT:
case opcode.TRYL:
nextIP := ctx.NextIP()
catchArg := b[nextIP-8:]
_, err := c.replaceLabelWithOffset(ctx.IP(), catchArg)
if err != nil {
return nil, err
}
finallyArg := b[nextIP-4:]
_, err := c.replaceLabelWithOffset(ctx.IP(), finallyArg)
_, err = c.replaceLabelWithOffset(ctx.IP(), finallyArg)
if err != nil {
return nil, err
}
@ -1886,6 +1942,9 @@ func shortenJumps(b []byte, offsets []int) []byte {
offset += calcOffsetCorrection(ip, ip+offset, offsets)
b[nextIP-1] = byte(offset)
case opcode.TRY:
catchOffset := int(int8(b[nextIP-2]))
catchOffset += calcOffsetCorrection(ip, ip+catchOffset, offsets)
b[nextIP-1] = byte(catchOffset)
finallyOffset := int(int8(b[nextIP-1]))
finallyOffset += calcOffsetCorrection(ip, ip+finallyOffset, offsets)
b[nextIP-1] = byte(finallyOffset)
@ -1898,7 +1957,11 @@ func shortenJumps(b []byte, offsets []int) []byte {
offset += calcOffsetCorrection(ip, ip+offset, offsets)
binary.LittleEndian.PutUint32(arg, uint32(offset))
case opcode.TRYL:
arg := b[nextIP-4:]
arg := b[nextIP-8:]
catchOffset := int(int32(binary.LittleEndian.Uint32(arg)))
catchOffset += calcOffsetCorrection(ip, ip+catchOffset, offsets)
binary.LittleEndian.PutUint32(arg, uint32(catchOffset))
arg = b[nextIP-4:]
finallyOffset := int(int32(binary.LittleEndian.Uint32(arg)))
finallyOffset += calcOffsetCorrection(ip, ip+finallyOffset, offsets)
binary.LittleEndian.PutUint32(arg, uint32(finallyOffset))