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vm: get rid of recursive (*VM).execute calls

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Recursive execute() calls can affect gas calculation.
This commit makes execute() be called only for real opcodes
and moves duplicate logic for CALL/JMP into a separate function.
This commit is contained in:
Evgenii Stratonikov 2020-01-21 13:48:59 +03:00
parent 4eae55143f
commit 7a6d6f43ce
1 changed files with 30 additions and 23 deletions
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53
pkg/vm/vm.go
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@ -1105,34 +1105,23 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
v.estack.PushVal(len(arr))
case opcode.JMP, opcode.JMPIF, opcode.JMPIFNOT:
var (
rOffset = int16(binary.LittleEndian.Uint16(parameter))
offset = ctx.ip + int(rOffset)
)
if offset < 0 || offset > len(ctx.prog) {
panic(fmt.Sprintf("JMP: invalid offset %d ip at %d", offset, ctx.ip))
}
offset := v.getJumpOffset(ctx, parameter)
cond := true
if op > opcode.JMP {
cond = v.estack.Pop().Bool()
if op == opcode.JMPIFNOT {
cond = !cond
}
}
if cond {
ctx.nextip = offset
if op != opcode.JMP {
cond = v.estack.Pop().Bool() == (op == opcode.JMPIF)
}
v.jumpIf(ctx, offset, cond)
case opcode.CALL:
v.checkInvocationStackSize()
newCtx := ctx.Copy()
newCtx.rvcount = -1
v.istack.PushVal(newCtx)
err = v.execute(v.Context(), opcode.JMP, parameter)
if err != nil {
return
}
offset := v.getJumpOffset(newCtx, parameter)
v.jumpIf(newCtx, offset, true)
case opcode.SYSCALL:
interopID := GetInteropID(parameter)
@ -1401,10 +1390,8 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
v.estack = newCtx.estack
v.astack = newCtx.astack
if op == opcode.CALLI {
err = v.execute(v.Context(), opcode.JMP, parameter[2:])
if err != nil {
return
}
offset := v.getJumpOffset(newCtx, parameter[2:])
v.jumpIf(newCtx, offset, true)
}
case opcode.THROW:
@ -1421,6 +1408,26 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
return
}
// jumpIf performs jump to offset if cond is true.
func (v *VM) jumpIf(ctx *Context, offset int, cond bool) {
if cond {
ctx.nextip = offset
}
}
// getJumpOffset returns instruction number in a current context
// to a which JMP should be performed.
// parameter is interpreted as little-endian int16.
func (v *VM) getJumpOffset(ctx *Context, parameter []byte) int {
rOffset := int16(binary.LittleEndian.Uint16(parameter))
offset := ctx.ip + int(rOffset)
if offset < 0 || offset > len(ctx.prog) {
panic(fmt.Sprintf("JMP: invalid offset %d ip at %d", offset, ctx.ip))
}
return offset
}
func cloneIfStruct(item StackItem) StackItem {
switch it := item.(type) {
case *StructItem: