aot: enable post-Byzantium & no input => no copy

* Enable WASM precompiles after the Byzantium fork since the WASM code
  is modelled after that code.
* x86 glue would go into an infinite loop if the size of the data to
  copy was zero as it would cycle back to 0xffffffffffffffff

core/vm/aot.go

@@ -24,7 +24,9 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
+	"github.com/ethereum/go-ethereum/common"
 	"log"
+	"math/big"
 	"os"
 	"reflect"
 	"syscall"
@@ -121,8 +123,8 @@ func (ac *AoTContract) ResolveGlobal(module, field string, t wa.Type) (init uint
 	return
 }
 
-func (ac *AoTContract) RequiredGas(code []byte) uint64 {
-	return 0
+func (ac *AoTContract) RequiredGas(input []byte) uint64 {
+	return PrecompiledContractsByzantium[common.BigToAddress(big.NewInt(int64(ac.Num)))].RequiredGas(input)
 }
 
 func (ac *AoTContract) Run(input []byte, contract *Contract) ([]byte, error) {
@@ -231,21 +233,13 @@ func (ac *AoTContract) Run(input []byte, contract *Contract) ([]byte, error) {
 
 	retaddr, retsize := aot.Exec(textAddr, stackLimit, memoryAddr, stackPtr)
 
-	gasLeft := binary.LittleEndian.Uint64(contractData[8:])
-	if gasLeft == 0xffffffffffffffff {
-		fmt.Println("Out of gas")
-		return nil, ErrOutOfGas
-	} else {
-		fmt.Println("gas left: ", gasLeft, "result: ", globalsMemory[retaddr+obj.MemoryOffset:retaddr+obj.MemoryOffset+retsize])
-		contract.Gas = gasLeft
-		if retsize == 0 {
-			return nil, nil
-		}
-
-		retData := make([]byte, retsize)
-		copy(retData, globalsMemory[retaddr+obj.MemoryOffset:retaddr+obj.MemoryOffset+retsize])
-		return retData, nil
+	if retsize == 0 {
+		return nil, nil
 	}
 
+	retData := make([]byte, retsize)
+	copy(retData, globalsMemory[retaddr+obj.MemoryOffset:retaddr+obj.MemoryOffset+retsize])
+	return retData, nil
+
 	// TODO cleanup all protected memory areas
 }

core/vm/aot/eei_amd64.s

@@ -36,13 +36,15 @@ TEXT ethereumUseGas<>(SB),NOSPLIT,$0
 	// Get pointer to the contract info area into r13
 	MOVQ    -0x20(R15), R13
 
-	MOVQ    8(SP), AX		// Gas required
-	MOVQ	0x8(R13), CX	// Gas left
-	CMPQ	AX, CX
-	JA		oog
+	// Disable gas accounting as it is currently implemented
+	// before calling the precompile.
+	//MOVQ    8(SP), AX		// Gas required
+	//MOVQ	0x8(R13), CX	// Gas left
+	//CMPQ	AX, CX
+	//JA		oog
 	
-	SUBQ	AX, CX
-	MOVQ	CX, 0x8(R13)
+	//SUBQ	AX, CX
+	//MOVQ	CX, 0x8(R13)
 	XORQ	AX, AX
 	XORQ	CX, CX
 	RET
@@ -80,6 +82,10 @@ TEXT ethereumCallDataCopy<>(SB),NOSPLIT,$0
 	CMPQ	AX, R12
 	JA		eei_error
 
+	// Skip copy loop if there are no data to copy
+	CMPQ	AX, $0
+	JZ		calldatacopy_end
+
 	// Load address of the destination buffer
 	MOVQ	0x18(SP), DI
 	ADDQ	R14, DI
@@ -90,6 +96,7 @@ TEXT ethereumCallDataCopy<>(SB),NOSPLIT,$0
 	ADDQ	$1, SI
 	ADDQ	$1, DI
 	LOOP	copy
+calldatacopy_end:
 	RET
 
 	eei_error:

core/vm/evm.go

@@ -45,9 +45,6 @@ func run(evm *EVM, contract *Contract, input []byte, readOnly bool) ([]byte, err
 	if contract.CodeAddr != nil {
 		precompiles := PrecompiledContractsHomestead
 		if evm.ChainConfig().IsByzantium(evm.BlockNumber) {
-			precompiles = PrecompiledContractsByzantium
-		}
-		if evm.ChainConfig().IsEWASM(evm.BlockNumber) {
 			precompiles = PrecompiledContractsEWASM
 		}
 		if p := precompiles[*contract.CodeAddr]; p != nil {

params/config.go

@@ -104,6 +104,7 @@ var (
 		ByzantiumBlock:      big.NewInt(1035301),
 		ConstantinopleBlock: big.NewInt(3660663),
 		PetersburgBlock:     big.NewInt(4321234),
+		EWASMBlock:          nil,
 		Clique: &CliqueConfig{
 			Period: 15,
 			Epoch:  30000,