wip: vm opcodes: Implement RETURNDATASIZE and RETURNDATACOPY

[whilei]

This change is 

[tzdybal]

Reviewed 10 of 10 files at r1.
Reviewable status: all files reviewed, 4 unresolved discussions (waiting on @whilei)

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core/vm/instructions.go, line 307 at r1 (raw file):

	)

	end := new(big.Int).Add(cOff, l)

Lol, looks like add(cOff, 1) (add one) not add(cOff, l) (add lowercase L). Rename l to len or something.

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core/vm/instructions.go, line 308 at r1 (raw file):

	end := new(big.Int).Add(cOff, l)
	if end.BitLen() > 64 || uint64(len(env.ReturnData())) < end.Uint64() {

Actually, if 2^32 <= end <= 2^64, we're doing unnecessary work ;) (as len returns int). This is not a big issue.
Another thing - I would use end.IsUint64() for clarity.

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core/vm/jump_table.go, line 26 at r1 (raw file):

	writes bool
	// returns determines whether the operation sets the return data
	returns bool

Same as with writes in previous review - I would create a function IsReturning(op OpCode) bool, and list the 5 opcodes there, instead of adding this to jumpPtr.

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core/vm/runtime/env.go, line 44 at r1 (raw file):

	getHashFn func(uint64) common.Hash

	readOnly   bool   // Whether to throw on stateful modifications

readOnly and returnData is repeated in 3 "Env" structs. This doesn't look good.nnn

[whilei]

Reviewable status: all files reviewed, 4 unresolved discussions (waiting on @whilei)

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core/vm/instructions.go, line 307 at r1 (raw file):

Previously, tzdybal (Tomasz Zdybał) wrote…

Lol, looks like add(cOff, 1) (add one) not add(cOff, l) (add lowercase L). Rename l to len or something.

Doing.

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core/vm/instructions.go, line 308 at r1 (raw file):

Previously, tzdybal (Tomasz Zdybał) wrote…

Actually, if 2^32 <= end <= 2^64, we're doing unnecessary work ;) (as len returns int). This is not a big issue.
Another thing - I would use end.IsUint64() for clarity.

Roger, doing the IsUint64

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core/vm/jump_table.go, line 26 at r1 (raw file):

Previously, tzdybal (Tomasz Zdybał) wrote…

Same as with writes in previous review - I would create a function IsReturning(op OpCode) bool, and list the 5 opcodes there, instead of adding this to jumpPtr.

Doing.